diff --git a/i.c b/i.c
index 81834db..937448f 100644
--- a/i.c
+++ b/i.c
@@ -93,19 +93,31 @@ static obj *init_modules(obj *r, obj *sp, obj *hp);
 #define VM_STACK_RSZ  64   /* red zone for overflow checks */
 #define VM_STACK_GSZ  (VM_STACK_LEN-VM_STACK_RSZ)
 
+/* box representation extras */
+#define boxbsz()      hbsz(1+1)
+#define hend_box()    (*--hp = obj_from_size(BOX_BTAG), hendblk(1+1))
+
+/* pair representation extras */
+#define pairbsz()     hbsz(2+1)
+#define hend_pair()   (*--hp = obj_from_size(PAIR_BTAG), hendblk(2+1))
+
+/* vector representation extras */
+#define vecbsz(n)     hbsz((n)+1)
+#define hend_vec(n)   (*--hp = obj_from_size(VECTOR_BTAG), hendblk((n)+1))
+
 /* vm closure representation */
 #ifdef NDEBUG /* quick */
 #define isvmclo(x)    (isobjptr(x) && isobjptr(hblkref(x, 0)))
 #define vmcloref(x,i) hblkref(x, i)
 #define vmclolen(x)   hblklen(x)
 #define vmclobsz(c)   hbsz(c)
-#define hpushvmclo(c) hendblk(c)
+#define hend_vmclo(c) hendblk(c)
 #else /* slow but thorough */
 #define isvmclo       isprocedure
 #define vmcloref      *procedureref
 #define vmclolen      procedurelen
 #define vmclobsz(c)   hbsz(c)
-#define hpushvmclo(c) hendblk(c)
+#define hend_vmclo(c) hendblk(c)
 #endif
 
 /* vm tuple representation (c != 1) */
@@ -113,7 +125,7 @@ static obj *init_modules(obj *r, obj *sp, obj *hp);
 #define tupleref      recordref
 #define tuplelen      recordlen
 #define tuplebsz(c)   hbsz((c)+2)
-#define hpushtuple(c) (*--hp = 0, *--hp = obj_from_size(RECORD_BTAG), hendblk((c)+2))
+#define hend_tuple(c) (*--hp = 0, *--hp = obj_from_size(RECORD_BTAG), hendblk((c)+2))
 
 /* in/re-loading gc-save shadow registers */
 #define unload_ip()   (rx = obj_from_fixnum(ip - &vectorref(vmcloref(rd, 0), 0)))
@@ -142,12 +154,31 @@ static void _sck(obj *s) {
 #define sgrow(n)      (sp += (n))
 #endif
 
+/* reserving heap memory inside instructions */
 #define hp_reserve(n) do { \
  if (unlikely(hp < cxg_heap + (n))) { \
    unload_ac(); unload_ip();   \
    hp = cxm_hgc(r, sp, hp, n); \
    reload_ac(); reload_ip();   \
  } } while (0)
+#define hp_reserve_inline(n) \
+ ((hp < cxg_heap + (n)) \
+ ? (unload_ac(), unload_ip(), hp = cxm_hgc(r, sp, hp, (n)), reload_ac(), reload_ip(), hp) \
+ : hp)
+#define hp_pushptr(p, pt) \
+  (hp_reserve_inline(2), *--hp = (obj)(p), *--hp = (obj)(pt), (obj)(hp+1))   
+
+/* small object representation extras */
+#define bool_obj(b) obj_from_bool(b)
+#define char_obj(b) obj_from_char(b)
+#define eof_obj() mkeof()
+#define fixnum_obj(x) obj_from_fixnum(x)
+#define flonum_obj(x) hp_pushptr(dupflonum(x), FLONUM_NTAG)
+#define string_obj(s) hp_pushptr((s), STRING_NTAG)
+#define iport_file_obj(fp) hp_pushptr((fp), IPORT_FILE_NTAG)
+#define oport_file_obj(fp) hp_pushptr((fp), OPORT_FILE_NTAG)
+#define iport_string_obj(fp) hp_pushptr((fp), IPORT_STRING_NTAG)
+#define oport_string_obj(fp) hp_pushptr((fp), OPORT_STRING_NTAG)
 
 /* cxi instructions protocol; retval is new hp: */
 typedef obj* regcall (*ins_t)(IPARAMS);
@@ -233,7 +264,7 @@ jump:
     /* r[0] = k; r[1] = code */
     hreserve(vmclobsz(1), 2); /* 2 live regs */
     *--hp = r[1];
-    r[2] = hpushvmclo(1);
+    r[2] = hend_vmclo(1);
     r[1] = obj_from_ktrap();
     pc = objptr_from_obj(r[0])[0];
     rc = 3;
@@ -388,7 +419,7 @@ define_instrhelper(cxi_fail) {
 define_instrhelper(cxi_failactype) { 
   char *msg = (char*)spop(); obj p;
   fprintf(stderr, "run-time failure: argument is not a %s:\n", msg); 
-  p = mkoport_file(sp-r, stderr); spush(p);
+  p = oport_file_obj(stderr); spush(p);
   oportputcircular(ac, p, 0);
   fputc('\n', stderr);
   spop();
@@ -473,17 +504,16 @@ define_instruction(dclose) {
   hp_reserve(vmclobsz(c));
   for (i = n-1; i >= 0; --i) *--hp = sref(i); /* display */
   *--hp = *ip++; /* code */
-  ac = hpushvmclo(c); /* closure */
+  ac = hend_vmclo(c); /* closure */
   sdrop(n);   
   gonexti();
 }
 
 define_instruction(sbox) {
   int i = fixnum_from_obj(*ip++); 
-  hp_reserve(hbsz(1+1));
+  hp_reserve(boxbsz());
   *--hp = sref(i);  
-  *--hp = obj_from_size(BOX_BTAG); 
-  sref(i) = hendblk(1+1);
+  sref(i) = hend_box();
   gonexti();
 }
 
@@ -542,8 +572,8 @@ define_instruction(appl) {
   int n, i; obj l = spop(), t = l;
   for (n = 0; ispair(t); t = cdr(t)) ++n; sgrow(n);
   for (i = 0; i < n; ++i, l = cdr(l)) sref(i) = car(l);
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0);
-  ac = obj_from_fixnum(n); /* argc */
+  ckx(ac); rd = ac; rx = fixnum_obj(0);
+  ac = fixnum_obj(n); /* argc */
   callsubi();
 }
 
@@ -557,16 +587,16 @@ define_instruction(cwmv) {
     sp = r + VM_REGC; /* stack is empty */
     memcpy(sp, &vmcloref(x, 1), n*sizeof(obj));
     sp += n; /* contains n elements now */
-    rd = t; rx = obj_from_fixnum(0); 
-    ac = obj_from_fixnum(0);
+    rd = t; rx = fixnum_obj(0); 
+    ac = fixnum_obj(0);
     callsubi();
   } else { 
     /* arrange return to cwmv code w/x */
     spush(x);
     spush(cx_callmv_2Dadapter_2Dclosure); 
-    spush(obj_from_fixnum(0));
+    spush(fixnum_obj(0));
     /* call the producer */
-    rd = t; rx = obj_from_fixnum(0); ac = obj_from_fixnum(0); 
+    rd = t; rx = fixnum_obj(0); ac = fixnum_obj(0); 
     callsubi(); 
   }
 }
@@ -575,14 +605,14 @@ define_instruction(rcmv) {
   /* single-value producer call returns here with result in ac, cns on stack */
   obj val = ac, x = spop();
   /* tail-call the consumer with the returned value */
-  spush(val); ac = obj_from_fixnum(1);
-  rd = x; rx = obj_from_fixnum(0); 
+  spush(val); ac = fixnum_obj(1);
+  rd = x; rx = fixnum_obj(0); 
   callsubi();
 }
 
 define_instruction(sdmv) {
   /* sending values on stack, ac contains argc */
-  if (ac == obj_from_fixnum(1)) {
+  if (ac == fixnum_obj(1)) {
     /* can return anywhere, including rcmv */
     ac = spop();
     rx = spop();
@@ -591,16 +621,16 @@ define_instruction(sdmv) {
   } else {
     /* can only pseudo-return to rcmv */
     int n = fixnum_from_obj(ac), m = 3, i;
-    if (sref(n) == obj_from_fixnum(0) && sref(n+1) == cx_callmv_2Dadapter_2Dclosure) {
+    if (sref(n) == fixnum_obj(0) && sref(n+1) == cx_callmv_2Dadapter_2Dclosure) {
       /* tail-call the consumer with the produced values */
-      rd = sref(n+2); rx = obj_from_fixnum(0); /* cns */
+      rd = sref(n+2); rx = fixnum_obj(0); /* cns */
       /* NB: can be sped up for popular cases: n == 0, n == 2 */
       memmove((void*)(sp-n-m), (void*)(sp-n), (size_t)n*sizeof(obj));
       sdrop(m); callsubi();
     } else { /* return args as a tuple (n != 1) */
       hp_reserve(tuplebsz(n));
       for (i = n-1; i >= 0; --i) *--hp = sref(i);
-      ac = hpushtuple(n);
+      ac = hend_tuple(n);
       sdrop(n);
       rx = spop();
       rd = spop();
@@ -616,7 +646,7 @@ define_instruction(lck) {
   hp_reserve(vmclobsz(n+1));
   hp -= n; memcpy(hp, sp-n-m, n*sizeof(obj));
   *--hp = cx_continuation_2Dadapter_2Dcode;
-  ac = hpushvmclo(n+1);
+  ac = hend_vmclo(n+1);
   gonexti();
 }
 
@@ -626,7 +656,7 @@ define_instruction(lck0) {
   hp_reserve(vmclobsz(n+1));
   hp -= n; memcpy(hp, sp-n, n*sizeof(obj));
   *--hp = cx_continuation_2Dadapter_2Dcode;
-  ac = hendblk(n+1);
+  ac = hend_vmclo(n+1);
   gonexti();
 }
 
@@ -639,8 +669,8 @@ define_instruction(wck) {
   sp = r + VM_REGC; /* stack is empty */
   memcpy(sp, &vmcloref(x, 1), n*sizeof(obj));
   sp += n; /* contains n elements now */
-  rd = t; rx = obj_from_fixnum(0); 
-  ac = obj_from_fixnum(0);
+  rd = t; rx = fixnum_obj(0); 
+  ac = fixnum_obj(0);
   callsubi();
 }
 
@@ -661,15 +691,15 @@ define_instruction(wckr) {
 
 define_instruction(rck) {
   /* in: ac:argc, args on stack, rd display is saved stack */
-  if (ac == obj_from_fixnum(1)) { /* easy, popular case */
+  if (ac == fixnum_obj(1)) { /* easy, popular case */
     ac = rd; 
     goi(wckr);
   } else { /* multiple results case */
     int c = fixnum_from_obj(ac), n = vmclolen(rd) - 1, i;
     obj *ks = &vmcloref(rd, 1), *ke = ks + n;
-    if (ke-ks > 3 && *--ke == obj_from_fixnum(0) && *--ke == cx_callmv_2Dadapter_2Dclosure) {
+    if (ke-ks > 3 && *--ke == fixnum_obj(0) && *--ke == cx_callmv_2Dadapter_2Dclosure) {
       obj *sb = r + VM_REGC;
-      rd = *--ke; rx = obj_from_fixnum(0); n = ke - ks; /* cns */
+      rd = *--ke; rx = fixnum_obj(0); n = ke - ks; /* cns */
       /* arrange stack as follows: [ks..ke] [arg ...] */
       assert((cxg_rend - cxg_regs - VM_REGC) > n + c);
       if (c) memmove(sb+n, sp-c, c*sizeof(obj));
@@ -678,7 +708,7 @@ define_instruction(rck) {
     } else { /* return args as a tuple (c != 1) */
       hp_reserve(tuplebsz(c));
       for (i = c-1; i >= 0; --i) *--hp = sref(i);
-      ac = hpushtuple(c);
+      ac = hend_tuple(c);
       sdrop(c);
       spush(ac);
       ac = rd;
@@ -690,7 +720,7 @@ define_instruction(rck) {
 define_instruction(save) {
   int dx = fixnum_from_obj(*ip++); 
   spush(rd);
-  spush(obj_from_fixnum(ip + dx - &vectorref(vmcloref(rd, 0), 0)));  
+  spush(fixnum_obj(ip + dx - &vectorref(vmcloref(rd, 0), 0)));  
   gonexti();
 }
 
@@ -700,7 +730,7 @@ define_instruction(jdceq) {
   obj v = *ip++, i = *ip++;
   if (ac == v) {
     rd = dref(fixnum_from_obj(i));
-    rx = obj_from_fixnum(0);
+    rx = fixnum_obj(0);
     callsubi();
   }
   gonexti();
@@ -710,7 +740,7 @@ define_instruction(jdcge) {
   obj v = *ip++, i = *ip++;
   if (ac >= v) { /* unsigned tagged fixnums can be compared as-is */
     rd = dref(fixnum_from_obj(i));
-    rx = obj_from_fixnum(0);
+    rx = fixnum_obj(0);
     callsubi();
   }
   gonexti();
@@ -719,21 +749,21 @@ define_instruction(jdcge) {
 define_instruction(jdref) {
   int i = fixnum_from_obj(*ip++); 
   rd = dref(i); 
-  rx = obj_from_fixnum(0);
+  rx = fixnum_obj(0);
   callsubi();
 }
 
 define_instruction(call) {
   int n = fixnum_from_obj(*ip++); 
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); 
-  ac = obj_from_fixnum(n); /* argc */
+  ckx(ac); rd = ac; rx = fixnum_obj(0); 
+  ac = fixnum_obj(n); /* argc */
   callsubi();
 }
 
 define_instruction(scall) {
   int m = fixnum_from_obj(*ip++), n = fixnum_from_obj(*ip++);
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); 
-  ac = obj_from_fixnum(n); /* argc */
+  ckx(ac); rd = ac; rx = fixnum_obj(0); 
+  ac = fixnum_obj(n); /* argc */
   memmove((void*)(sp-n-m), (void*)(sp-n), (size_t)n*sizeof(obj));
   sdrop(m);
   callsubi();
@@ -779,18 +809,17 @@ define_instruction(shrarg) {
     spush(mknull());
   } else {
     obj l = mknull();
-    hp_reserve(hbsz(2+1)*m);
+    hp_reserve(pairbsz()*m);
     while (m > 0) { 
       *--hp = l; *--hp = sref(n + m - 1);
-      *--hp = obj_from_size(PAIR_BTAG); 
-      l = hendblk(2+1); 
+      l = hend_pair(); 
       --m;
     }
     memmove((void*)(sp-c), (void*)(sp-n), (size_t)n*sizeof(obj));
     sdrop(c-n);
     spush(l); 
   }
-  ac = obj_from_fixnum(n+1);
+  ac = fixnum_obj(n+1);
   gonexti();
 }
 
@@ -807,7 +836,7 @@ define_instruction(shlit) {
 
 define_instruction(shi0) { 
   spush(ac);
-  ac = obj_from_fixnum(0);
+  ac = fixnum_obj(0);
   gonexti();
 }
 
@@ -834,19 +863,19 @@ define_instruction(ckz) { ckz(ac); gonexti(); }
 
 define_instruction(isq) {
   obj x = ac, y = spop();
-  ac = obj_from_bool(x == y);
+  ac = bool_obj(x == y);
   gonexti(); 
 }
 
 define_instruction(isv) {
   obj x = ac, y = spop();
-  ac = obj_from_bool(iseqv(x,y));
+  ac = bool_obj(iseqv(x,y));
   gonexti(); 
 }
 
 define_instruction(ise) {
   obj x = ac, y = spop();
-  ac = obj_from_bool(isequal(x,y));
+  ac = bool_obj(isequal(x,y));
   gonexti(); 
 }
 
@@ -854,10 +883,9 @@ define_instruction(unbox) { ckz(ac); ac = boxref(ac); gonexti(); }
 define_instruction(setbox) { ckz(ac); boxref(ac) = spop(); gonexti(); }
 
 define_instruction(box) {
-  hp_reserve(hbsz(1+1));
+  hp_reserve(boxbsz());
   *--hp = ac;
-  *--hp = obj_from_size(BOX_BTAG);
-  ac = hendblk(1+1);
+  ac = hend_box();
   gonexti();
 }
 
@@ -873,37 +901,35 @@ define_instruction(cddr) { ckp(ac); ac = cdr(ac); ckp(ac); ac = cdr(ac); gonexti
 
 
 define_instruction(nullp) {
-  ac = obj_from_bool(isnull(ac));
+  ac = bool_obj(isnull(ac));
   gonexti();
 }
 
 define_instruction(pairp) {
-  ac = obj_from_bool(ispair(ac));
+  ac = bool_obj(ispair(ac));
   gonexti();
 }
 
 define_instruction(cons) {
-  hp_reserve(hbsz(2+1));
+  hp_reserve(pairbsz());
   *--hp = spop(); /* cdr */
   *--hp = ac;     /* car */
-  *--hp = obj_from_size(PAIR_BTAG);
-  ac = hendblk(2+1);
+  ac = hend_pair();
   gonexti();
 }
 
 define_instruction(listp) {
-  ac = obj_from_bool(islist(ac));
+  ac = bool_obj(islist(ac));
   gonexti();
 }
 
 define_instruction(list) {
   int i, n = fixnum_from_obj(*ip++);
-  hp_reserve(hbsz(2+1)*n);
+  hp_reserve(pairbsz()*n);
   for (ac = mknull(), i = n-1; i >= 0; --i) {
     *--hp = ac;      /* cdr */
     *--hp = sref(i); /* car */
-    *--hp = obj_from_size(PAIR_BTAG);
-    ac = hendblk(2+1);
+    ac = hend_pair();
   }
   sdrop(n);
   gonexti();
@@ -912,13 +938,12 @@ define_instruction(list) {
 define_instruction(lmk) {
   int i, n; obj v; ckk(ac);
   n = fixnum_from_obj(ac); 
-  hp_reserve(hbsz(2+1)*n); v = sref(0);
+  hp_reserve(pairbsz()*n); v = sref(0);
   ac = mknull();
   for (i = 0; i < n; ++i) {
     *--hp = ac; /* cdr */
     *--hp = v;  /* car */
-    *--hp = obj_from_size(PAIR_BTAG);
-    ac = hendblk(2+1);
+    ac = hend_pair();
   }
   sdrop(1);
   gonexti();
@@ -927,7 +952,7 @@ define_instruction(lmk) {
 define_instruction(llen) {
   int n = 0;
   while (ispair(ac)) { ac = cdr(ac); ++n; }
-  ac = obj_from_fixnum(n);
+  ac = fixnum_obj(n);
   gonexti();
 }
 
@@ -953,7 +978,7 @@ define_instruction(memq) {
   for (; ispair(l); l = cdr(l)) {
     if (car(l) == ac) { ac = l; gonexti(); }
   }
-  ac = obj_from_bool(0);
+  ac = bool_obj(0);
   gonexti();
 }
 
@@ -972,7 +997,7 @@ define_instruction(assq) {
   for (; ispair(l); l = cdr(l)) {
     obj p = car(l); if (ispair(p) && car(p) == ac) { ac = p; gonexti(); }
   }
-  ac = obj_from_bool(0);
+  ac = bool_obj(0);
   gonexti();
 }
 
@@ -994,7 +1019,7 @@ define_instruction(ltail) {
 }
 
 define_instruction(lpair) {
-  obj l = obj_from_bool(0);
+  obj l = bool_obj(0);
   while (ispair(ac)) { l = ac; ac = cdr(ac); }
   ac = l;
   gonexti();
@@ -1003,10 +1028,10 @@ define_instruction(lpair) {
 define_instruction(lrev) {
   obj l = ac, o = mknull(); int n = 0;
   while (ispair(ac)) { ac = cdr(ac); ++n; }
-  hp_reserve(hbsz(2+1)*n);
+  hp_reserve(pairbsz()*n);
   for (ac = l; ac != mknull(); ac = cdr(ac)) { 
     *--hp = o; *--hp = car(ac);
-    *--hp = obj_from_size(PAIR_BTAG); o = hendblk(2+1); 
+    o = hend_pair(); 
   }
   ac = o;
   gonexti();
@@ -1020,18 +1045,18 @@ define_instruction(lrevi) {
 }
 
 define_instruction(charp) {
-  ac = obj_from_bool(ischar(ac));
+  ac = bool_obj(ischar(ac));
   gonexti();
 }
 
 define_instruction(strp) {
-  ac = obj_from_bool(isstring(ac));
+  ac = bool_obj(isstring(ac));
   gonexti();
 }
 
 define_instruction(str) {
   int i, n = fixnum_from_obj(*ip++);
-  obj o = hpushstr(sp-r, allocstring(n, ' '));
+  obj o = string_obj(allocstring(n, ' '));
   unsigned char *s = (unsigned char *)stringchars(o);
   for (i = 0; i < n; ++i) {
     obj x = sref(i); ckc(x); s[i] = char_from_obj(x);
@@ -1044,13 +1069,13 @@ define_instruction(smk) {
   int n, c; obj x = spop(); 
   ckk(ac); ckc(x);
   n = fixnum_from_obj(ac), c = char_from_obj(x);
-  ac = hpushstr(sp-r, allocstring(n, c)); 
+  ac = string_obj(allocstring(n, c)); 
   gonexti();
 }
 
 define_instruction(slen) {
   cks(ac);
-  ac = obj_from_fixnum(stringlen(ac));
+  ac = fixnum_obj(stringlen(ac));
   gonexti();
 }
 
@@ -1059,7 +1084,7 @@ define_instruction(sget) {
   cks(ac); ckk(x); 
   i = fixnum_from_obj(x); 
   if (i >= stringlen(ac)) failtype(x, "valid string index");
-  ac = obj_from_char(*stringref(ac, i));
+  ac = char_obj(*stringref(ac, i));
   gonexti();
 }
 
@@ -1076,7 +1101,7 @@ define_instruction(scat) {
   obj x = ac, y = spop(); int *d; 
   cks(x); cks(y);
   d = stringcat(stringdata(x), stringdata(y));
-  ac = hpushstr(sp-r, d);
+  ac = string_obj(d);
   gonexti();
 }
 
@@ -1087,21 +1112,20 @@ define_instruction(ssub) {
   if (is > ie) failtype(x, "valid start string index");
   if (ie > stringlen(ac)) failtype(y, "valid end string index");
   d = substring(stringdata(ac), is, ie);
-  ac = hpushstr(sp-r, d);
+  ac = string_obj(d);
   gonexti();
 }
 
 define_instruction(vecp) {
-  ac = obj_from_bool(isvector(ac));
+  ac = bool_obj(isvector(ac));
   gonexti();
 }
 
 define_instruction(vec) {
   int i, n = fixnum_from_obj(*ip++);
-  hp_reserve(hbsz(n+1));
+  hp_reserve(vecbsz(n));
   for (i = n-1; i >= 0; --i) *--hp = sref(i);
-  *--hp = obj_from_size(VECTOR_BTAG);
-  ac = hendblk(n+1);
+  ac = hend_vec(n);
   sdrop(n);
   gonexti();
 }
@@ -1109,17 +1133,16 @@ define_instruction(vec) {
 define_instruction(vmk) {
   int i, n; obj v; ckk(ac);
   n = fixnum_from_obj(ac); 
-  hp_reserve(hbsz(n+1)); v = sref(0);
+  hp_reserve(vecbsz(n)); v = sref(0);
   for (i = 0; i < n; ++i) *--hp = v;
-  *--hp = obj_from_size(VECTOR_BTAG);
-  ac = hendblk(n+1);
+  ac = hend_vec(n);
   sdrop(1);
   gonexti();
 }
 
 define_instruction(vlen) {
   ckv(ac);
-  ac = obj_from_fixnum(vectorlen(ac));
+  ac = fixnum_obj(vectorlen(ac));
   gonexti();
 }
 
@@ -1145,12 +1168,11 @@ define_instruction(vcat) {
   obj x = ac, y = sref(0); int n1, n2, n;
   ckv(x); ckv(y);
   n1 = vectorlen(x), n2 = vectorlen(y), n = n1 + n2;
-  hp_reserve(hbsz(n+1));
+  hp_reserve(vecbsz(n));
   /* NB: vectorref fails to return pointer to empty vector's start */
   hp -= n2; if (n2) memcpy(hp, &vectorref(y, 0), n2*sizeof(obj));
   hp -= n1; if (n1) memcpy(hp, &vectorref(x, 0), n1*sizeof(obj));
-  *--hp = obj_from_size(VECTOR_BTAG);
-  ac = hendblk(n+1);
+  ac = hend_vec(n);
   sdrop(1);
   gonexti();
 }
@@ -1158,11 +1180,10 @@ define_instruction(vcat) {
 define_instruction(vtol) {
   obj l = mknull(); int n;
   ckv(ac); n = vectorlen(ac);
-  hp_reserve(hbsz(2+1)*n);
+  hp_reserve(pairbsz()*n);
   while (n > 0) {
     *--hp = l; *--hp = vectorref(ac, n-1);
-    *--hp = obj_from_size(PAIR_BTAG);
-    l = hendblk(2+1);
+    l = hend_pair();
     --n;
   }
   ac = l;
@@ -1172,21 +1193,19 @@ define_instruction(vtol) {
 define_instruction(ltov) {
   obj l = ac; int n = 0, i;
   while (ispair(l)) { l = cdr(l); ++n; }
-  hp_reserve(hbsz(n+1));
+  hp_reserve(vecbsz(n));
   for (l = ac, i = 0, hp -= n; i < n; ++i, l = cdr(l)) hp[i] = car(l);
-  *--hp = obj_from_size(VECTOR_BTAG);
-  ac = hendblk(n+1);
+  ac = hend_vec(n);
   gonexti();
 }
 
 define_instruction(stol) {
   obj l = mknull(); int n;
   cks(ac); n = stringlen(ac);
-  hp_reserve(hbsz(2+1)*n);
+  hp_reserve(pairbsz()*n);
   while (n > 0) {
-    *--hp = l; *--hp = obj_from_char(*stringref(ac, n-1));
-    *--hp = obj_from_size(PAIR_BTAG);
-    l = hendblk(2+1);
+    *--hp = l; *--hp = char_obj(*stringref(ac, n-1));
+    l = hend_pair();
     --n;
   }
   ac = l;
@@ -1199,13 +1218,13 @@ define_instruction(ltos) {
   d = allocstring(n, ' ');
   for (i = 0; i < n; ac = cdr(ac), ++i)
     sdatachars(d)[i] = char_from_obj(car(ac));
-  ac = hpushstr(sp-r, d);
+  ac = string_obj(d);
   gonexti();
 }
 
 define_instruction(ytos) {
   cky(ac);
-  ac = hpushstr(sp-r, newstring(symbolname(getsymbol(ac))));
+  ac = string_obj(newstring(symbolname(getsymbol(ac))));
   gonexti();
 }
 
@@ -1226,7 +1245,7 @@ define_instruction(itos) {
   do { int d = num % radix; *--s = d < 10 ? d + '0' : d - 10 + 'a'; }
   while (num /= radix);
   if (neg) *--s = '-';
-  ac = hpushstr(sp-r, newstring(s));  
+  ac = string_obj(newstring(s));  
   gonexti();
 }
 
@@ -1240,20 +1259,20 @@ define_instruction(stoi) {
   else if (s[0] == '#' && (s[1] == 'd' || s[1] == 'D')) s += 2, radix = 10;
   else if (s[0] == '#' && (s[1] == 'x' || s[1] == 'X')) s += 2, radix = 16;
   l = (errno = 0, strtol(s, &e, radix));
-  if (errno || l < FIXNUM_MIN || l > FIXNUM_MAX || e == s || *e) ac = obj_from_bool(0);
-  else ac = obj_from_fixnum(l);
+  if (errno || l < FIXNUM_MIN || l > FIXNUM_MAX || e == s || *e) ac = bool_obj(0);
+  else ac = fixnum_obj(l);
   gonexti();
 }
 
 define_instruction(ctoi) {
   ckc(ac);
-  ac = obj_from_fixnum(char_from_obj(ac));
+  ac = fixnum_obj(char_from_obj(ac));
   gonexti();
 }
 
 define_instruction(itoc) {
   cki(ac); /* TODO: range check? */
-  ac = obj_from_char(fixnum_from_obj(ac));
+  ac = char_obj(fixnum_from_obj(ac));
   gonexti();
 }
 
@@ -1264,7 +1283,7 @@ define_instruction(jtos) {
   if (d != d) strcpy(buf, "+nan.0"); else if (d <= -HUGE_VAL) strcpy(buf, "-inf.0");
   else if (d >= HUGE_VAL) strcpy(buf, "+inf.0"); else if (*s == 'E') *s = 'e'; 
   else if (*s == 0) {  *s++ = '.'; *s++ = '0'; *s = 0; }
-  ac = hpushstr(sp-r, newstring(buf));
+  ac = string_obj(newstring(buf));
   gonexti();
 }
 
@@ -1275,14 +1294,14 @@ define_instruction(stoj) {
   else if (strcmp_ci(s+1, "inf.0") == 0) d = (*s == '-' ? -HUGE_VAL : HUGE_VAL); 
   else if (strcmp_ci(s+1, "nan.0") == 0) d = HUGE_VAL - HUGE_VAL; 
   else d = strtod(s, &e);
-  if (errno || e == s || *e) ac = obj_from_bool(0);
-  else ac = obj_from_flonum(sp-r, d);
+  if (errno || e == s || *e) ac = bool_obj(0);
+  else ac = flonum_obj(d);
   gonexti();
 }
 
 define_instruction(ntos) {
   if (is_fixnum_obj(ac)) goi(itos);
-  if (unlikely(spop() != obj_from_fixnum(10))) fail("non-10 radix in flonum conversion");
+  if (unlikely(spop() != fixnum_obj(10))) fail("non-10 radix in flonum conversion");
   goi(jtos);
 }
 
@@ -1292,77 +1311,77 @@ define_instruction(ston) {
   s = stringchars(x); radix = fixnum_from_obj(y);
   if (radix < 2 || radix > 10 + 'z' - 'a') failtype(y, "valid radix");
   switch (strtofxfl(s, radix, &l, &d)) {
-    case 'e': ac = obj_from_fixnum(l); break;
-    case 'i': ac = obj_from_flonum(sp-r, d); break;
-    default : ac = obj_from_bool(0); break;
+    case 'e': ac = fixnum_obj(l); break;
+    case 'i': ac = flonum_obj(d); break;
+    default : ac = bool_obj(0); break;
   }
   gonexti();
 }
 
 define_instruction(not) {
-  ac = obj_from_bool(ac == 0);
+  ac = bool_obj(ac == 0);
   gonexti();
 }
 
 define_instruction(izerop) {
   cki(ac);
-  ac = obj_from_bool(ac == obj_from_fixnum(0));
+  ac = bool_obj(ac == fixnum_obj(0));
   gonexti();
 }
 
 define_instruction(iposp) {
   cki(ac);
-  ac = obj_from_bool(fixnum_from_obj(ac) > 0);
+  ac = bool_obj(fixnum_from_obj(ac) > 0);
   gonexti(); 
 }
 
 define_instruction(inegp) {
   cki(ac);
-  ac = obj_from_bool(fixnum_from_obj(ac) < 0);
+  ac = bool_obj(fixnum_from_obj(ac) < 0);
   gonexti(); 
 }
 
 define_instruction(ievnp) {
   cki(ac);
-  ac = obj_from_bool((fixnum_from_obj(ac) & 1) == 0);
+  ac = bool_obj((fixnum_from_obj(ac) & 1) == 0);
   gonexti(); 
 }
 
 define_instruction(ioddp) {
   cki(ac);
-  ac = obj_from_bool((fixnum_from_obj(ac) & 1) != 0);
+  ac = bool_obj((fixnum_from_obj(ac) & 1) != 0);
   gonexti(); 
 }
 
 define_instruction(iadd) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fxadd(fixnum_from_obj(x), fixnum_from_obj(y)));
+  ac = fixnum_obj(fxadd(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(isub) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fxsub(fixnum_from_obj(x), fixnum_from_obj(y)));
+  ac = fixnum_obj(fxsub(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(imul) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fxmul(fixnum_from_obj(x), fixnum_from_obj(y)));
+  ac = fixnum_obj(fxmul(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(iquo) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  if (y == obj_from_fixnum(0)) fail("division by zero");
-  ac = obj_from_fixnum(fxquo(fixnum_from_obj(x), fixnum_from_obj(y)));
+  if (y == fixnum_obj(0)) fail("division by zero");
+  ac = fixnum_obj(fxquo(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(irem) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  if (y == obj_from_fixnum(0)) fail("division by zero");
-  ac = obj_from_fixnum(fxrem(fixnum_from_obj(x), fixnum_from_obj(y)));
+  if (y == fixnum_obj(0)) fail("division by zero");
+  ac = fixnum_obj(fxrem(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
@@ -1380,271 +1399,271 @@ define_instruction(imax) {
 
 define_instruction(ineg) {
   cki(ac);
-  ac = obj_from_fixnum(fxneg(fixnum_from_obj(ac)));
+  ac = fixnum_obj(fxneg(fixnum_from_obj(ac)));
   gonexti();
 }
 
 define_instruction(iabs) {
   cki(ac);
-  ac = obj_from_fixnum(fxabs(fixnum_from_obj(ac)));
+  ac = fixnum_obj(fxabs(fixnum_from_obj(ac)));
   gonexti();
 }
 
 define_instruction(itoj) {
   cki(ac);
-  ac = obj_from_flonum(sp-r, (double)fixnum_from_obj(ac));
+  ac = flonum_obj((double)fixnum_from_obj(ac));
   gonexti();
 }
 
 define_instruction(idiv) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  if (y == obj_from_fixnum(0)) fail("division by zero");
-  ac = obj_from_fixnum(fxdiv(fixnum_from_obj(x), fixnum_from_obj(y)));
+  if (y == fixnum_obj(0)) fail("division by zero");
+  ac = fixnum_obj(fxdiv(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(imqu) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  if (y == obj_from_fixnum(0)) fail("division by zero");
-  ac = obj_from_fixnum(fxmqu(fixnum_from_obj(x), fixnum_from_obj(y)));
+  if (y == fixnum_obj(0)) fail("division by zero");
+  ac = fixnum_obj(fxmqu(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(imlo) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  if (y == obj_from_fixnum(0)) fail("division by zero");
-  ac = obj_from_fixnum(fxmlo(fixnum_from_obj(x), fixnum_from_obj(y)));
+  if (y == fixnum_obj(0)) fail("division by zero");
+  ac = fixnum_obj(fxmlo(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(ieuq) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  if (y == obj_from_fixnum(0)) fail("division by zero");
-  ac = obj_from_fixnum(fxeuq(fixnum_from_obj(x), fixnum_from_obj(y)));
+  if (y == fixnum_obj(0)) fail("division by zero");
+  ac = fixnum_obj(fxeuq(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(ieur) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  if (y == obj_from_fixnum(0)) fail("division by zero");
-  ac = obj_from_fixnum(fxeur(fixnum_from_obj(x), fixnum_from_obj(y)));
+  if (y == fixnum_obj(0)) fail("division by zero");
+  ac = fixnum_obj(fxeur(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(igcd) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fxgcd(fixnum_from_obj(x), fixnum_from_obj(y)));
+  ac = fixnum_obj(fxgcd(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(ipow) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fxpow(fixnum_from_obj(x), fixnum_from_obj(y)));
+  ac = fixnum_obj(fxpow(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(isqrt) {
   cki(ac); /* TODO: check for negative */
-  ac = obj_from_fixnum(fxsqrt(fixnum_from_obj(ac)));
+  ac = fixnum_obj(fxsqrt(fixnum_from_obj(ac)));
   gonexti();
 }
 
 define_instruction(inot) {
   cki(ac);
-  ac = obj_from_fixnum(~fixnum_from_obj(ac));
+  ac = fixnum_obj(~fixnum_from_obj(ac));
   gonexti();
 }
 
 define_instruction(iand) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fixnum_from_obj(x) & fixnum_from_obj(y));
+  ac = fixnum_obj(fixnum_from_obj(x) & fixnum_from_obj(y));
   gonexti();
 }
 
 define_instruction(iior) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fixnum_from_obj(x) | fixnum_from_obj(y));
+  ac = fixnum_obj(fixnum_from_obj(x) | fixnum_from_obj(y));
   gonexti();
 }
 
 define_instruction(ixor) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fixnum_from_obj(x) ^ fixnum_from_obj(y));
+  ac = fixnum_obj(fixnum_from_obj(x) ^ fixnum_from_obj(y));
   gonexti();
 }
 
 define_instruction(iasl) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fxasl(fixnum_from_obj(x), fixnum_from_obj(y)));
+  ac = fixnum_obj(fxasl(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(iasr) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_fixnum(fxasr(fixnum_from_obj(x), fixnum_from_obj(y)));
+  ac = fixnum_obj(fxasr(fixnum_from_obj(x), fixnum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(ilt) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_bool(fixnum_from_obj(x) < fixnum_from_obj(y));
+  ac = bool_obj(fixnum_from_obj(x) < fixnum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(igt) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_bool(fixnum_from_obj(x) > fixnum_from_obj(y));
+  ac = bool_obj(fixnum_from_obj(x) > fixnum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(ile) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_bool(fixnum_from_obj(x) <= fixnum_from_obj(y));
+  ac = bool_obj(fixnum_from_obj(x) <= fixnum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(ige) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_bool(fixnum_from_obj(x) >= fixnum_from_obj(y));
+  ac = bool_obj(fixnum_from_obj(x) >= fixnum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(ieq) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_bool(x == y);
+  ac = bool_obj(x == y);
   gonexti(); 
 }
 
 define_instruction(ine) {
   obj x = ac, y = spop(); cki(x); cki(y);
-  ac = obj_from_bool(x != y);
+  ac = bool_obj(x != y);
   gonexti(); 
 }
 
 
 define_instruction(jzerop) {
   ckj(ac);
-  ac = obj_from_bool(flonum_from_obj(ac) == 0.0);
+  ac = bool_obj(flonum_from_obj(ac) == 0.0);
   gonexti();
 }
 
 define_instruction(jposp) {
   ckj(ac);
-  ac = obj_from_bool(flonum_from_obj(ac) > 0.0);
+  ac = bool_obj(flonum_from_obj(ac) > 0.0);
   gonexti(); 
 }
 
 define_instruction(jnegp) {
   ckj(ac);
-  ac = obj_from_bool(flonum_from_obj(ac) < 0.0);
+  ac = bool_obj(flonum_from_obj(ac) < 0.0);
   gonexti(); 
 }
 
 define_instruction(jevnp) {
   double f; ckj(ac);
   f = flonum_from_obj(ac);
-  ac = obj_from_bool(flisint(f / 2.0));
+  ac = bool_obj(flisint(f / 2.0));
   gonexti(); 
 }
 
 define_instruction(joddp) {
   double f; ckj(ac);
   f = flonum_from_obj(ac);
-  ac = obj_from_bool(flisint((f + 1.0) / 2.0));
+  ac = bool_obj(flisint((f + 1.0) / 2.0));
   gonexti(); 
 }
 
 define_instruction(jintp) {
   double f; ckj(ac);
   f = flonum_from_obj(ac);
-  ac = obj_from_bool(f > -HUGE_VAL && f < HUGE_VAL && f == floor(f));
+  ac = bool_obj(f > -HUGE_VAL && f < HUGE_VAL && f == floor(f));
   gonexti(); 
 }
 
 define_instruction(jnanp) {
   double f; ckj(ac);
   f = flonum_from_obj(ac);
-  ac = obj_from_bool(f != f);
+  ac = bool_obj(f != f);
   gonexti(); 
 }
 
 define_instruction(jfinp) {
   double f; ckj(ac);
   f = flonum_from_obj(ac);
-  ac = obj_from_bool(f > -HUGE_VAL && f < HUGE_VAL);
+  ac = bool_obj(f > -HUGE_VAL && f < HUGE_VAL);
   gonexti(); 
 }
 
 define_instruction(jinfp) {
   double f; ckj(ac);
   f = flonum_from_obj(ac);
-  ac = obj_from_bool(f <= -HUGE_VAL || f >= HUGE_VAL);
+  ac = bool_obj(f <= -HUGE_VAL || f >= HUGE_VAL);
   gonexti(); 
 }
 
 define_instruction(jadd) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, flonum_from_obj(x) + flonum_from_obj(y));
+  ac = flonum_obj(flonum_from_obj(x) + flonum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(jsub) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, flonum_from_obj(x) - flonum_from_obj(y));
+  ac = flonum_obj(flonum_from_obj(x) - flonum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(jmul) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, flonum_from_obj(x) * flonum_from_obj(y));
+  ac = flonum_obj(flonum_from_obj(x) * flonum_from_obj(y));
   gonexti();
 }
 
 define_instruction(jdiv) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, flonum_from_obj(x) / flonum_from_obj(y));
+  ac = flonum_obj(flonum_from_obj(x) / flonum_from_obj(y));
   gonexti();
 }
 
 define_instruction(jrem) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, flrem(flonum_from_obj(x), flonum_from_obj(y)));
+  ac = flonum_obj(flrem(flonum_from_obj(x), flonum_from_obj(y)));
   gonexti();
 }
 
 define_instruction(jlt) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_bool(flonum_from_obj(x) < flonum_from_obj(y));
+  ac = bool_obj(flonum_from_obj(x) < flonum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(jgt) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_bool(flonum_from_obj(x) > flonum_from_obj(y));
+  ac = bool_obj(flonum_from_obj(x) > flonum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(jle) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_bool(flonum_from_obj(x) <= flonum_from_obj(y));
+  ac = bool_obj(flonum_from_obj(x) <= flonum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(jge) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_bool(flonum_from_obj(x) >= flonum_from_obj(y));
+  ac = bool_obj(flonum_from_obj(x) >= flonum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(jeq) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_bool(flonum_from_obj(x) == flonum_from_obj(y));
+  ac = bool_obj(flonum_from_obj(x) == flonum_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(jne) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_bool(flonum_from_obj(x) != flonum_from_obj(y));
+  ac = bool_obj(flonum_from_obj(x) != flonum_from_obj(y));
   gonexti(); 
 }
 
@@ -1662,67 +1681,67 @@ define_instruction(jmax) {
 
 define_instruction(jneg) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, -flonum_from_obj(ac));
+  ac = flonum_obj(-flonum_from_obj(ac));
   gonexti(); 
 }
 
 define_instruction(jabs) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, fabs(flonum_from_obj(ac)));
+  ac = flonum_obj(fabs(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jgcd) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, flgcd(flonum_from_obj(x), flonum_from_obj(y)));
+  ac = flonum_obj(flgcd(flonum_from_obj(x), flonum_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(jpow) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, pow(flonum_from_obj(x), flonum_from_obj(y)));
+  ac = flonum_obj(pow(flonum_from_obj(x), flonum_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(jsqrt) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, sqrt(flonum_from_obj(ac)));
+  ac = flonum_obj(sqrt(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jtoi) {
   ckj(ac);
-  ac = obj_from_fixnum(fxflo(flonum_from_obj(ac)));
+  ac = fixnum_obj(fxflo(flonum_from_obj(ac)));
   gonexti();
 }
 
 define_instruction(jquo) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, flquo(flonum_from_obj(x), flonum_from_obj(y)));
+  ac = flonum_obj(flquo(flonum_from_obj(x), flonum_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(jmqu) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, flmqu(flonum_from_obj(x), flonum_from_obj(y)));
+  ac = flonum_obj(flmqu(flonum_from_obj(x), flonum_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(jmlo) {
   obj x = ac, y = spop(); ckj(x); ckj(y);
-  ac = obj_from_flonum(sp-r, flmlo(flonum_from_obj(x), flonum_from_obj(y)));
+  ac = flonum_obj(flmlo(flonum_from_obj(x), flonum_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(jfloor) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, floor(flonum_from_obj(ac)));
+  ac = flonum_obj(floor(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jceil) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, ceil(flonum_from_obj(ac)));
+  ac = flonum_obj(ceil(flonum_from_obj(ac)));
   gonexti(); 
 }
 
@@ -1730,71 +1749,71 @@ define_instruction(jtrunc) {
   double f, i; ckj(ac);
   f = flonum_from_obj(ac);
   modf(f,  &i);
-  ac = obj_from_flonum(sp-r, i);
+  ac = flonum_obj(i);
   gonexti(); 
 }
 
 define_instruction(jround) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, flround(flonum_from_obj(ac)));
+  ac = flonum_obj(flround(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jexp) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, exp(flonum_from_obj(ac)));
+  ac = flonum_obj(exp(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jlog) {
   obj x = ac, y = spop(); ckj(ac);
   if (likely(!y)) {
-    ac = obj_from_flonum(sp-r, log(flonum_from_obj(ac)));
+    ac = flonum_obj(log(flonum_from_obj(ac)));
   } else {
     double b; ckj(y); b = flonum_from_obj(y);
-    if (likely(b == 10.0)) ac = obj_from_flonum(sp-r, log10(flonum_from_obj(ac)));
-    else ac = obj_from_flonum(sp-r, log(flonum_from_obj(ac))/log(b));
+    if (likely(b == 10.0)) ac = flonum_obj(log10(flonum_from_obj(ac)));
+    else ac = flonum_obj(log(flonum_from_obj(ac))/log(b));
   }
   gonexti(); 
 }
 
 define_instruction(jsin) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, sin(flonum_from_obj(ac)));
+  ac = flonum_obj(sin(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jcos) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, cos(flonum_from_obj(ac)));
+  ac = flonum_obj(cos(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jtan) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, tan(flonum_from_obj(ac)));
+  ac = flonum_obj(tan(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jasin) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, asin(flonum_from_obj(ac)));
+  ac = flonum_obj(asin(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jacos) {
   ckj(ac);
-  ac = obj_from_flonum(sp-r, acos(flonum_from_obj(ac)));
+  ac = flonum_obj(acos(flonum_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(jatan) {
   obj x = ac, y = spop(); ckj(ac);
   if (likely(!y)) {
-    ac = obj_from_flonum(sp-r, atan(flonum_from_obj(x)));
+    ac = flonum_obj(atan(flonum_from_obj(x)));
   } else {
     ckj(y); 
-    ac = obj_from_flonum(sp-r, atan2(flonum_from_obj(x), flonum_from_obj(y)));
+    ac = flonum_obj(atan2(flonum_from_obj(x), flonum_from_obj(y)));
   }
   gonexti(); 
 }
@@ -1803,23 +1822,23 @@ define_instruction(jatan) {
 define_instruction(zerop) {
   obj x = ac;
   if (likely(is_fixnum_obj(x))) {
-    ac = obj_from_bool(x == obj_from_fixnum(0));
+    ac = bool_obj(x == fixnum_obj(0));
   } else if (likely(is_flonum_obj(x))) {
-    ac = obj_from_bool(flonum_from_obj(x) == 0.0);
+    ac = bool_obj(flonum_from_obj(x) == 0.0);
   } else failactype("number");
   gonexti();
 }
 
 define_instruction(posp) {
-  if (likely(is_fixnum_obj(ac))) ac = obj_from_bool(get_fixnum_unchecked(ac) > 0);
-  else if (likely(is_flonum_obj(ac))) ac = obj_from_bool(flonum_from_obj(ac) > 0.0);
+  if (likely(is_fixnum_obj(ac))) ac = bool_obj(get_fixnum_unchecked(ac) > 0);
+  else if (likely(is_flonum_obj(ac))) ac = bool_obj(flonum_from_obj(ac) > 0.0);
   else failactype("number");
   gonexti(); 
 }
 
 define_instruction(negp) {
-  if (likely(is_fixnum_obj(ac))) ac = obj_from_bool(get_fixnum_unchecked(ac) < 0);
-  else if (likely(is_flonum_obj(ac))) ac = obj_from_bool(flonum_from_obj(ac) < 0.0);
+  if (likely(is_fixnum_obj(ac))) ac = bool_obj(get_fixnum_unchecked(ac) < 0);
+  else if (likely(is_flonum_obj(ac))) ac = bool_obj(flonum_from_obj(ac) < 0.0);
   else failactype("number");
   gonexti(); 
 }
@@ -1827,7 +1846,7 @@ define_instruction(negp) {
 define_instruction(add) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    ac = obj_from_fixnum(fxadd(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
+    ac = fixnum_obj(fxadd(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1836,7 +1855,7 @@ define_instruction(add) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, dx + dy);
+    ac = flonum_obj(dx + dy);
   }
   gonexti(); 
 }
@@ -1844,7 +1863,7 @@ define_instruction(add) {
 define_instruction(sub) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    ac = obj_from_fixnum(fxsub(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
+    ac = fixnum_obj(fxsub(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1853,7 +1872,7 @@ define_instruction(sub) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, dx - dy);
+    ac = flonum_obj(dx - dy);
   }
   gonexti(); 
 }
@@ -1861,7 +1880,7 @@ define_instruction(sub) {
 define_instruction(mul) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    ac = obj_from_fixnum(fxmul(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
+    ac = fixnum_obj(fxmul(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1870,7 +1889,7 @@ define_instruction(mul) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, dx * dy);
+    ac = flonum_obj(dx * dy);
   }
   gonexti(); 
 }
@@ -1879,9 +1898,9 @@ define_instruction(div) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
     long i; double d;
-    if (unlikely(y == obj_from_fixnum(0))) fail("division by zero");
-    if (fxifdv(get_fixnum_unchecked(x), get_fixnum_unchecked(y), &i, &d)) ac = obj_from_fixnum(i);
-    else obj_from_flonum(sp-r, d);
+    if (unlikely(y == fixnum_obj(0))) fail("division by zero");
+    if (fxifdv(get_fixnum_unchecked(x), get_fixnum_unchecked(y), &i, &d)) ac = fixnum_obj(i);
+    else flonum_obj(d);
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1890,7 +1909,7 @@ define_instruction(div) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, dx / dy);
+    ac = flonum_obj(dx / dy);
   }
   gonexti(); 
 }
@@ -1898,8 +1917,8 @@ define_instruction(div) {
 define_instruction(quo) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    if (unlikely(y == obj_from_fixnum(0))) fail("division by zero");
-    ac = obj_from_fixnum(fxquo(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
+    if (unlikely(y == fixnum_obj(0))) fail("division by zero");
+    ac = fixnum_obj(fxquo(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1908,7 +1927,7 @@ define_instruction(quo) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, flquo(dx, dy));
+    ac = flonum_obj(flquo(dx, dy));
   }
   gonexti(); 
 }
@@ -1916,8 +1935,8 @@ define_instruction(quo) {
 define_instruction(rem) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    if (unlikely(y == obj_from_fixnum(0))) fail("division by zero");
-    ac = obj_from_fixnum(fxrem(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
+    if (unlikely(y == fixnum_obj(0))) fail("division by zero");
+    ac = fixnum_obj(fxrem(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1926,7 +1945,7 @@ define_instruction(rem) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, flrem(dx, dy));
+    ac = flonum_obj(flrem(dx, dy));
   }
   gonexti(); 
 }
@@ -1934,8 +1953,8 @@ define_instruction(rem) {
 define_instruction(mqu) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    if (unlikely(y == obj_from_fixnum(0))) fail("division by zero");
-    ac = obj_from_fixnum(fxmqu(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
+    if (unlikely(y == fixnum_obj(0))) fail("division by zero");
+    ac = fixnum_obj(fxmqu(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1944,7 +1963,7 @@ define_instruction(mqu) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, flmqu(dx, dy));
+    ac = flonum_obj(flmqu(dx, dy));
   }
   gonexti(); 
 }
@@ -1952,8 +1971,8 @@ define_instruction(mqu) {
 define_instruction(mlo) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    if (unlikely(y == obj_from_fixnum(0))) fail("division by zero");
-    ac = obj_from_fixnum(fxmlo(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
+    if (unlikely(y == fixnum_obj(0))) fail("division by zero");
+    ac = fixnum_obj(fxmlo(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1962,7 +1981,7 @@ define_instruction(mlo) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, flmlo(dx, dy));
+    ac = flonum_obj(flmlo(dx, dy));
   }
   gonexti(); 
 }
@@ -1971,7 +1990,7 @@ define_instruction(mlo) {
 define_instruction(lt) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    ac = obj_from_bool(get_fixnum_unchecked(x) < get_fixnum_unchecked(y));
+    ac = bool_obj(get_fixnum_unchecked(x) < get_fixnum_unchecked(y));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1980,7 +1999,7 @@ define_instruction(lt) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_bool(dx < dy);
+    ac = bool_obj(dx < dy);
   }
   gonexti(); 
 }
@@ -1988,7 +2007,7 @@ define_instruction(lt) {
 define_instruction(gt) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    ac = obj_from_bool(get_fixnum_unchecked(x) > get_fixnum_unchecked(y));
+    ac = bool_obj(get_fixnum_unchecked(x) > get_fixnum_unchecked(y));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -1997,7 +2016,7 @@ define_instruction(gt) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_bool(dx > dy);
+    ac = bool_obj(dx > dy);
   }
   gonexti(); 
 }
@@ -2005,7 +2024,7 @@ define_instruction(gt) {
 define_instruction(le) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    ac = obj_from_bool(get_fixnum_unchecked(x) <= get_fixnum_unchecked(y));
+    ac = bool_obj(get_fixnum_unchecked(x) <= get_fixnum_unchecked(y));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -2014,7 +2033,7 @@ define_instruction(le) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_bool(dx <= dy);
+    ac = bool_obj(dx <= dy);
   }
   gonexti(); 
 }
@@ -2022,7 +2041,7 @@ define_instruction(le) {
 define_instruction(ge) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    ac = obj_from_bool(get_fixnum_unchecked(x) >= get_fixnum_unchecked(y));
+    ac = bool_obj(get_fixnum_unchecked(x) >= get_fixnum_unchecked(y));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -2031,14 +2050,14 @@ define_instruction(ge) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_bool(dx >= dy);
+    ac = bool_obj(dx >= dy);
   }
   gonexti(); 
 }
 
 define_instruction(eq) {
   obj x = ac, y = spop();
-  if (x == y) ac = obj_from_bool(1);
+  if (x == y) ac = bool_obj(1);
   else if (is_flonum_obj(x) || is_flonum_obj(y)) {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -2047,14 +2066,14 @@ define_instruction(eq) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_bool(dx == dy);
-  } else ac = obj_from_bool(0);
+    ac = bool_obj(dx == dy);
+  } else ac = bool_obj(0);
   gonexti(); 
 }
 
 define_instruction(ne) {
   obj x = ac, y = spop();
-  if (x == y) ac = obj_from_bool(0);
+  if (x == y) ac = bool_obj(0);
   else if (is_flonum_obj(x) || is_flonum_obj(y)) {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -2063,8 +2082,8 @@ define_instruction(ne) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_bool(dx != dy);
-  } else ac = obj_from_bool(1);
+    ac = bool_obj(dx != dy);
+  } else ac = bool_obj(1);
   gonexti(); 
 }
 
@@ -2080,7 +2099,7 @@ define_instruction(min) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = dx < dy ? obj_from_flonum(sp-r, dx) : obj_from_flonum(sp-r, dy);
+    ac = dx < dy ? flonum_obj(dx) : flonum_obj(dy);
   }
   gonexti(); 
 }
@@ -2097,7 +2116,7 @@ define_instruction(max) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = dx > dy ? obj_from_flonum(sp-r, dx) : obj_from_flonum(sp-r, dy);
+    ac = dx > dy ? flonum_obj(dx) : flonum_obj(dy);
   }
   gonexti(); 
 }
@@ -2105,7 +2124,7 @@ define_instruction(max) {
 define_instruction(gcd) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    ac = obj_from_fixnum(fxgcd(fixnum_from_obj(x), fixnum_from_obj(y)));
+    ac = fixnum_obj(fxgcd(fixnum_from_obj(x), fixnum_from_obj(y)));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -2114,7 +2133,7 @@ define_instruction(gcd) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, flgcd(dx, dy));
+    ac = flonum_obj(flgcd(dx, dy));
   }
   gonexti(); 
 }
@@ -2123,7 +2142,7 @@ define_instruction(pow) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
     /* fixme: this will either overflow, or fail on negative y */
-    ac = obj_from_fixnum(fxpow(fixnum_from_obj(x), fixnum_from_obj(y)));
+    ac = fixnum_obj(fxpow(fixnum_from_obj(x), fixnum_from_obj(y)));
   } else {
     double dx, dy;
     if (likely(is_flonum_obj(x))) dx = flonum_from_obj(x);
@@ -2132,19 +2151,19 @@ define_instruction(pow) {
     if (likely(is_flonum_obj(y))) dy = flonum_from_obj(y);
     else if (likely(is_fixnum_obj(y))) dy = (double)fixnum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, pow(dx, dy));
+    ac = flonum_obj(pow(dx, dy));
   }
   gonexti(); 
 }
 
 define_instruction(sqrt) {
   if (likely(is_flonum_obj(ac))) {
-    ac = obj_from_flonum(sp-r, sqrt(flonum_from_obj(ac)));
+    ac = flonum_obj(sqrt(flonum_from_obj(ac)));
   } else if (likely(is_fixnum_obj(ac))) {
     long x = fixnum_from_obj(ac), y;
-    if (x < 0) ac = obj_from_flonum(sp-r, (HUGE_VAL - HUGE_VAL));   
-    else if (y = fxsqrt(x), y*y == x) ac = obj_from_fixnum(y);
-    else ac = obj_from_flonum(sp-r, sqrt((double)x));
+    if (x < 0) ac = flonum_obj((HUGE_VAL - HUGE_VAL));   
+    else if (y = fxsqrt(x), y*y == x) ac = fixnum_obj(y);
+    else ac = flonum_obj(sqrt((double)x));
   } else failactype("number");
   gonexti(); 
 }
@@ -2154,7 +2173,7 @@ define_instruction(exp) {
   if (unlikely(is_fixnum_obj(ac))) x = (double)fixnum_from_obj(ac);
   else if (likely(is_flonum_obj(ac))) x = flonum_from_obj(ac);
   else failactype("number");
-  ac = obj_from_flonum(sp-r, exp(x));
+  ac = flonum_obj(exp(x));
   gonexti(); 
 }
 
@@ -2164,16 +2183,16 @@ define_instruction(log) {
   else if (likely(is_flonum_obj(ac))) x = flonum_from_obj(ac);
   else failactype("number");
   if (likely(!y)) {
-    ac = obj_from_flonum(sp-r, log(x));
-  } else if (likely(y == obj_from_fixnum(10))) {
-    ac = obj_from_flonum(sp-r, log10(x));
+    ac = flonum_obj(log(x));
+  } else if (likely(y == fixnum_obj(10))) {
+    ac = flonum_obj(log10(x));
   } else {
     double b; 
     if (unlikely(is_fixnum_obj(y))) b = (double)fixnum_from_obj(y);
     else if (likely(is_flonum_obj(y))) b = flonum_from_obj(y);
     else failtype(y, "number");
-    if (likely(b == 10.0)) ac = obj_from_flonum(sp-r, log10(x));
-    else ac = obj_from_flonum(sp-r, log(x)/log(b));
+    if (likely(b == 10.0)) ac = flonum_obj(log10(x));
+    else ac = flonum_obj(log(x)/log(b));
   }
   gonexti(); 
 }
@@ -2185,7 +2204,7 @@ define_instruction(sin) {
   } else if (likely(is_flonum_obj(ac))) {
     x = flonum_from_obj(ac);
   } else failactype("number");
-  ac = obj_from_flonum(sp-r, sin(x));
+  ac = flonum_obj(sin(x));
   gonexti(); 
 }
 
@@ -2196,7 +2215,7 @@ define_instruction(cos) {
   } else if (likely(is_flonum_obj(ac))) {
     x = flonum_from_obj(ac);
   } else failactype("number");
-  ac = obj_from_flonum(sp-r, cos(x));
+  ac = flonum_obj(cos(x));
   gonexti(); 
 }
 
@@ -2207,7 +2226,7 @@ define_instruction(tan) {
   } else if (likely(is_flonum_obj(ac))) {
     x = flonum_from_obj(ac);
   } else failactype("number");
-  ac = obj_from_flonum(sp-r, tan(x));
+  ac = flonum_obj(tan(x));
   gonexti(); 
 }
 
@@ -2218,7 +2237,7 @@ define_instruction(asin) {
   } else if (likely(is_flonum_obj(ac))) {
     x = flonum_from_obj(ac);
   } else failactype("number");
-  ac = obj_from_flonum(sp-r, asin(x));
+  ac = flonum_obj(asin(x));
   gonexti(); 
 }
 
@@ -2229,7 +2248,7 @@ define_instruction(acos) {
   } else if (likely(is_flonum_obj(ac))) {
     x = flonum_from_obj(ac);
   } else failactype("number");
-  ac = obj_from_flonum(sp-r, acos(x));
+  ac = flonum_obj(acos(x));
   gonexti(); 
 }
 
@@ -2239,38 +2258,38 @@ define_instruction(atan) {
   else if (likely(is_flonum_obj(ac))) x = flonum_from_obj(ac);
   else failactype("number");
   if (likely(!y)) {
-    ac = obj_from_flonum(sp-r, atan(x));
+    ac = flonum_obj(atan(x));
   } else {
     double b; 
     if (unlikely(is_fixnum_obj(y))) b = (double)fixnum_from_obj(y);
     else if (likely(is_flonum_obj(y))) b = flonum_from_obj(y);
     else failtype(y, "number");
-    ac = obj_from_flonum(sp-r, atan2(x, b));
+    ac = flonum_obj(atan2(x, b));
   }
   gonexti(); 
 }
 
 define_instruction(neg) {
   if (likely(is_fixnum_obj(ac))) {
-    ac = obj_from_fixnum(-fixnum_from_obj(ac));
+    ac = fixnum_obj(-fixnum_from_obj(ac));
   } else if (likely(is_flonum_obj(ac))) {
-    ac = obj_from_flonum(sp-r, -flonum_from_obj(ac));
+    ac = flonum_obj(-flonum_from_obj(ac));
   } else failactype("number");
   gonexti(); 
 }
 
 define_instruction(abs) {
   if (likely(is_fixnum_obj(ac))) {
-    ac = obj_from_fixnum(fxabs(fixnum_from_obj(ac)));
+    ac = fixnum_obj(fxabs(fixnum_from_obj(ac)));
   } else if (likely(is_flonum_obj(ac))) {
-    ac = obj_from_flonum(sp-r, fabs(flonum_from_obj(ac)));
+    ac = flonum_obj(fabs(flonum_from_obj(ac)));
   } else failactype("number");
   gonexti(); 
 }
 
 define_instruction(floor) {
   if (likely(is_flonum_obj(ac))) {
-    ac = obj_from_flonum(sp-r, floor(flonum_from_obj(ac)));
+    ac = flonum_obj(floor(flonum_from_obj(ac)));
   } else if (unlikely(!is_fixnum_obj(ac))) {
     failactype("number");
   }
@@ -2279,7 +2298,7 @@ define_instruction(floor) {
 
 define_instruction(ceil) {
   if (likely(is_flonum_obj(ac))) {
-    ac = obj_from_flonum(sp-r, ceil(flonum_from_obj(ac)));
+    ac = flonum_obj(ceil(flonum_from_obj(ac)));
   } else if (unlikely(!is_fixnum_obj(ac))) {
     failactype("number");
   }
@@ -2290,7 +2309,7 @@ define_instruction(trunc) {
   if (likely(is_flonum_obj(ac))) {
     double x = flonum_from_obj(ac);
     double i; modf(x,  &i);
-    ac = obj_from_flonum(sp-r, i);
+    ac = flonum_obj(i);
   } else if (unlikely(!is_fixnum_obj(ac))) {
     failactype("number");
   }
@@ -2299,7 +2318,7 @@ define_instruction(trunc) {
 
 define_instruction(round) {
   if (likely(is_flonum_obj(ac))) {
-    ac = obj_from_flonum(sp-r, flround(flonum_from_obj(ac)));
+    ac = flonum_obj(flround(flonum_from_obj(ac)));
   } else if (unlikely(!is_fixnum_obj(ac))) {
     failactype("number");
   }
@@ -2308,88 +2327,88 @@ define_instruction(round) {
 
 
 define_instruction(nump) {
-  ac = obj_from_bool(is_fixnum_obj(ac) || is_flonum_obj(ac));
+  ac = bool_obj(is_fixnum_obj(ac) || is_flonum_obj(ac));
   gonexti(); 
 }
 
 define_instruction(fixp) {
-  ac = obj_from_bool(is_fixnum_obj(ac));
+  ac = bool_obj(is_fixnum_obj(ac));
   gonexti(); 
 }
 
 define_instruction(flop) {
-  ac = obj_from_bool(is_flonum_obj(ac));
+  ac = bool_obj(is_flonum_obj(ac));
   gonexti(); 
 }
 
 define_instruction(intp) {
   if (likely(is_fixnum_obj(ac))) {
-    ac = obj_from_bool(1);
+    ac = bool_obj(1);
   } else { /* accepts any object! */
-    ac = obj_from_bool(is_flonum_obj(ac) && flisint(flonum_from_obj(ac)));
+    ac = bool_obj(is_flonum_obj(ac) && flisint(flonum_from_obj(ac)));
   }
   gonexti(); 
 }
 
 define_instruction(nanp) {
   if (unlikely(is_fixnum_obj(ac))) {
-    ac = obj_from_bool(0);
+    ac = bool_obj(0);
   } else if (likely(is_flonum_obj(ac))) {
     double f = flonum_from_obj(ac);
-    ac = obj_from_bool(f != f);
+    ac = bool_obj(f != f);
   } else failactype("number");
   gonexti(); 
 }
 
 define_instruction(finp) {
   if (unlikely(is_fixnum_obj(ac))) {
-    ac = obj_from_bool(1);
+    ac = bool_obj(1);
   } else if (likely(is_flonum_obj(ac))) {
     double f = flonum_from_obj(ac);
-    ac = obj_from_bool(f > -HUGE_VAL && f < HUGE_VAL);
+    ac = bool_obj(f > -HUGE_VAL && f < HUGE_VAL);
   } else failactype("number");
   gonexti(); 
 }
 
 define_instruction(infp) {
   if (unlikely(is_fixnum_obj(ac))) {
-    ac = obj_from_bool(0);
+    ac = bool_obj(0);
   } else if (likely(is_flonum_obj(ac))) {
     double f = flonum_from_obj(ac);
-    ac = obj_from_bool(f <= -HUGE_VAL || f >= HUGE_VAL);
+    ac = bool_obj(f <= -HUGE_VAL || f >= HUGE_VAL);
   } else failactype("number");
   gonexti(); 
 }
 
 define_instruction(evnp) {
   if (likely(is_fixnum_obj(ac))) {
-    ac = obj_from_bool((fixnum_from_obj(ac) & 1) == 0);
+    ac = bool_obj((fixnum_from_obj(ac) & 1) == 0);
   } else if (likely(is_flonum_obj(ac))) {
     double f = flonum_from_obj(ac);
-    ac = obj_from_bool(flisint(f / 2.0));
+    ac = bool_obj(flisint(f / 2.0));
   } else failactype("number");
   gonexti(); 
 }
 
 define_instruction(oddp) {
   if (likely(is_fixnum_obj(ac))) {
-    ac = obj_from_bool((fixnum_from_obj(ac) & 1) != 0);
+    ac = bool_obj((fixnum_from_obj(ac) & 1) != 0);
   } else if (likely(is_flonum_obj(ac))) {
     double f = flonum_from_obj(ac);
-    ac = obj_from_bool(flisint((f + 1.0) / 2.0));
+    ac = bool_obj(flisint((f + 1.0) / 2.0));
   } else failactype("number");
   gonexti(); 
 }
 
 define_instruction(ntoi) {
-  if (likely(is_flonum_obj(ac))) ac = obj_from_fixnum(fxflo(flonum_from_obj(ac)));
+  if (likely(is_flonum_obj(ac))) ac = fixnum_obj(fxflo(flonum_from_obj(ac)));
   else if (likely(is_fixnum_obj(ac))) /* keep ac as-is */ ;
   else failactype("number");
   gonexti(); 
 }
 
 define_instruction(ntoj) {
-  if (likely(is_fixnum_obj(ac))) ac = obj_from_flonum(sp-r, (flonum_t)fixnum_from_obj(ac));
+  if (likely(is_fixnum_obj(ac))) ac = flonum_obj((flonum_t)fixnum_from_obj(ac));
   else if (likely(is_flonum_obj(ac))) /* keep ac as-is */ ;
   else failactype("number");
   gonexti(); 
@@ -2399,12 +2418,11 @@ define_instruction(ntoj) {
 define_instruction(lcat) {
   obj t, l, *p, *d; int c;
   for (l = ac, c = 0; ispair(l); l = cdr(l)) ++c;
-  hp_reserve(hbsz(2+1)*c);
+  hp_reserve(pairbsz()*c);
   p = --sp; t = *p; /* pop & take addr */
   for (l = ac; ispair(l); l = cdr(l)) {
     *--hp = t; d = hp; *--hp = car(l);
-    *--hp = obj_from_size(PAIR_BTAG); 
-    *p = hendblk(2+1); p = d;
+    *p = hend_pair(); p = d;
   }
   ac = *sp;
   gonexti(); 
@@ -2413,133 +2431,133 @@ define_instruction(lcat) {
 define_instruction(ccmp) {
   obj x = ac, y = spop(); int cmp; ckc(x); ckc(y);
   cmp = char_from_obj(x) - char_from_obj(y);
-  ac = obj_from_fixnum(cmp);
+  ac = fixnum_obj(cmp);
   gonexti(); 
 }
 
 define_instruction(ceq) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(char_from_obj(x) == char_from_obj(y));
+  ac = bool_obj(char_from_obj(x) == char_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(clt) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(char_from_obj(x) < char_from_obj(y));
+  ac = bool_obj(char_from_obj(x) < char_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(cgt) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(char_from_obj(x) > char_from_obj(y));
+  ac = bool_obj(char_from_obj(x) > char_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(cle) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(char_from_obj(x) <= char_from_obj(y));
+  ac = bool_obj(char_from_obj(x) <= char_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(cge) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(char_from_obj(x) >= char_from_obj(y));
+  ac = bool_obj(char_from_obj(x) >= char_from_obj(y));
   gonexti(); 
 }
 
 define_instruction(cicmp) {
   obj x = ac, y = spop(); int cmp; ckc(x); ckc(y);
   cmp = tolower(char_from_obj(x)) - tolower(char_from_obj(y));
-  ac = obj_from_fixnum(cmp);
+  ac = fixnum_obj(cmp);
   gonexti(); 
 }
 
 define_instruction(cieq) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(tolower(char_from_obj(x)) == tolower(char_from_obj(y)));
+  ac = bool_obj(tolower(char_from_obj(x)) == tolower(char_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(cilt) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(tolower(char_from_obj(x)) < tolower(char_from_obj(y)));
+  ac = bool_obj(tolower(char_from_obj(x)) < tolower(char_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(cigt) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(tolower(char_from_obj(x)) > tolower(char_from_obj(y)));
+  ac = bool_obj(tolower(char_from_obj(x)) > tolower(char_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(cile) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(tolower(char_from_obj(x)) <= tolower(char_from_obj(y)));
+  ac = bool_obj(tolower(char_from_obj(x)) <= tolower(char_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(cige) {
   obj x = ac, y = spop(); ckc(x); ckc(y);
-  ac = obj_from_bool(tolower(char_from_obj(x)) >= tolower(char_from_obj(y)));
+  ac = bool_obj(tolower(char_from_obj(x)) >= tolower(char_from_obj(y)));
   gonexti(); 
 }
 
 define_instruction(cwsp) {
   ckc(ac);
-  ac = obj_from_bool(isspace(char_from_obj(ac)));
+  ac = bool_obj(isspace(char_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(clcp) {
   ckc(ac);
-  ac = obj_from_bool(islower(char_from_obj(ac)));
+  ac = bool_obj(islower(char_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(cucp) {
   ckc(ac);
-  ac = obj_from_bool(isupper(char_from_obj(ac)));
+  ac = bool_obj(isupper(char_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(calp) {
   ckc(ac);
-  ac = obj_from_bool(isalpha(char_from_obj(ac)));
+  ac = bool_obj(isalpha(char_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(cnup) {
   ckc(ac);
-  ac = obj_from_bool(isdigit(char_from_obj(ac)));
+  ac = bool_obj(isdigit(char_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(cupc) {
   ckc(ac);
-  ac = obj_from_char(toupper(char_from_obj(ac)));
+  ac = char_obj(toupper(char_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(cdnc) {
   ckc(ac);
-  ac = obj_from_char(tolower(char_from_obj(ac)));
+  ac = char_obj(tolower(char_from_obj(ac)));
   gonexti(); 
 }
 
 define_instruction(cflc) {
   ckc(ac);
-  ac = obj_from_char(tolower(char_from_obj(ac))); /* stub */
+  ac = char_obj(tolower(char_from_obj(ac))); /* stub */
   gonexti(); 
 }
 
 define_instruction(cdgv) {
   int ch; ckc(ac);
   ch = char_from_obj(ac);
-  if (likely('0' <= ch && ch <= '9')) ac = obj_from_fixnum(ch - '0');  
+  if (likely('0' <= ch && ch <= '9')) ac = fixnum_obj(ch - '0');  
   /* R7RS won't allow hex and any larger radix digits
-  else if (likely('a' <= ch && ch <= 'z')) ac = obj_from_fixnum(10 + ch - 'a');  
-  else if (likely('A' <= ch && ch <= 'Z')) ac = obj_from_fixnum(10 + ch - 'A'); */
-  else ac = obj_from_bool(0);
+  else if (likely('a' <= ch && ch <= 'z')) ac = fixnum_obj(10 + ch - 'a');  
+  else if (likely('A' <= ch && ch <= 'Z')) ac = fixnum_obj(10 + ch - 'A'); */
+  else ac = bool_obj(0);
   gonexti(); 
 }
 
@@ -2547,160 +2565,160 @@ define_instruction(cdgv) {
 define_instruction(scmp) {
   obj x = ac, y = spop(); int cmp; cks(x); cks(y);
   cmp = strcmp(stringchars(x), stringchars(y));
-  ac = obj_from_fixnum(cmp);
+  ac = fixnum_obj(cmp);
   gonexti(); 
 }
 
 define_instruction(seq) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp(stringchars(x), stringchars(y)) == 0);
+  ac = bool_obj(strcmp(stringchars(x), stringchars(y)) == 0);
   gonexti(); 
 }
 
 define_instruction(slt) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp(stringchars(x), stringchars(y)) < 0);
+  ac = bool_obj(strcmp(stringchars(x), stringchars(y)) < 0);
   gonexti(); 
 }
 
 define_instruction(sgt) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp(stringchars(x), stringchars(y)) > 0);
+  ac = bool_obj(strcmp(stringchars(x), stringchars(y)) > 0);
   gonexti(); 
 }
 
 define_instruction(sle) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp(stringchars(x), stringchars(y)) <= 0);
+  ac = bool_obj(strcmp(stringchars(x), stringchars(y)) <= 0);
   gonexti(); 
 }
 
 define_instruction(sge) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp(stringchars(x), stringchars(y)) >= 0);
+  ac = bool_obj(strcmp(stringchars(x), stringchars(y)) >= 0);
   gonexti(); 
 }
 
 define_instruction(sicmp) {
   obj x = ac, y = spop(); int cmp; cks(x); cks(y);
   cmp = strcmp_ci(stringchars(x), stringchars(y));
-  ac = obj_from_fixnum(cmp);
+  ac = fixnum_obj(cmp);
   gonexti(); 
 }
 
 define_instruction(sieq) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp_ci(stringchars(x), stringchars(y)) == 0);
+  ac = bool_obj(strcmp_ci(stringchars(x), stringchars(y)) == 0);
   gonexti(); 
 }
 
 define_instruction(silt) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp_ci(stringchars(x), stringchars(y)) < 0);
+  ac = bool_obj(strcmp_ci(stringchars(x), stringchars(y)) < 0);
   gonexti(); 
 }
 
 define_instruction(sigt) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp_ci(stringchars(x), stringchars(y)) > 0);
+  ac = bool_obj(strcmp_ci(stringchars(x), stringchars(y)) > 0);
   gonexti(); 
 }
 
 define_instruction(sile) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp_ci(stringchars(x), stringchars(y)) <= 0);
+  ac = bool_obj(strcmp_ci(stringchars(x), stringchars(y)) <= 0);
   gonexti(); 
 }
 
 define_instruction(sige) {
   obj x = ac, y = spop(); cks(x); cks(y);
-  ac = obj_from_bool(strcmp_ci(stringchars(x), stringchars(y)) >= 0);
+  ac = bool_obj(strcmp_ci(stringchars(x), stringchars(y)) >= 0);
   gonexti(); 
 }
 
 
 define_instruction(symp) {
-  ac = obj_from_bool(issymbol(ac));
+  ac = bool_obj(issymbol(ac));
   gonexti();
 }
 
 define_instruction(boolp) {
-  ac = obj_from_bool(is_bool_obj(ac));
+  ac = bool_obj(is_bool_obj(ac));
   gonexti();
 }
 
 define_instruction(boxp) {
-  ac = obj_from_bool(isbox(ac));
+  ac = bool_obj(isbox(ac));
   gonexti();
 }
 
 define_instruction(funp) {
-  ac = obj_from_bool(isvmclo(ac));
+  ac = bool_obj(isvmclo(ac));
   gonexti();
 }
 
 define_instruction(ipp) {
-  ac = obj_from_bool(isiport(ac));
+  ac = bool_obj(isiport(ac));
   gonexti();
 }
 
 define_instruction(opp) {
-  ac = obj_from_bool(isoport(ac));
+  ac = bool_obj(isoport(ac));
   gonexti();
 }
 
 define_instruction(sip) {
-  ac = mkiport_file(sp-r, stdin); /* TODO: keep in global var -- in r7rs it is a parameter */
+  ac = iport_file_obj(stdin); /* TODO: keep in global var -- in r7rs it is a parameter */
   gonexti();
 }
 
 define_instruction(sop) {
-  ac = mkoport_file(sp-r, stdout); /* TODO: keep in global var -- in r7rs it is a parameter */
+  ac = oport_file_obj(stdout); /* TODO: keep in global var -- in r7rs it is a parameter */
   gonexti();
 }
 
 define_instruction(sep) {
-  ac = mkoport_file(sp-r, stderr); /* TODO: keep in global var -- in r7rs it is a parameter */
+  ac = oport_file_obj(stderr); /* TODO: keep in global var -- in r7rs it is a parameter */
   gonexti();
 }
 
 define_instruction(ipop) {
   cxtype_iport_t *vt; ckr(ac); 
   vt = iportvt(ac); assert(vt);
-  ac = obj_from_bool(vt != (cxtype_iport_t *)IPORT_CLOSED_NTAG);
+  ac = bool_obj(vt != (cxtype_iport_t *)IPORT_CLOSED_NTAG);
   gonexti();
 }
 
 define_instruction(opop) {
   cxtype_oport_t *vt; ckw(ac); 
   vt = oportvt(ac); assert(vt);
-  ac = obj_from_bool(vt != (cxtype_oport_t *)OPORT_CLOSED_NTAG);
+  ac = bool_obj(vt != (cxtype_oport_t *)OPORT_CLOSED_NTAG);
   gonexti();
 }
 
 define_instruction(otip) {
   FILE *fp = fopen(stringchars(ac), "r");
   if (fp == NULL) fail("can't open input file");
-  ac = mkiport_file(sp-r, fp);
+  ac = iport_file_obj(fp);
   gonexti();
 }
 
 define_instruction(otop) {
   FILE *fp = fopen(stringchars(ac), "w");
   if (fp == NULL) fail("can't open output file");
-  ac = mkoport_file(sp-r, fp);
+  ac = oport_file_obj(fp);
   gonexti();
 }
 
 define_instruction(ois) {
   int *d; cks(ac);
   d = dupstring(stringdata(ac));
-  ac = mkiport_string(sp-r, sialloc(sdatachars(d), d));
+  ac = iport_string_obj(sialloc(sdatachars(d), d));
   gonexti();
 }
 
 define_instruction(oos) {
-  ac = mkoport_string(sp-r, newcb());
+  ac = oport_string_obj(newcb());
   gonexti();
 }
 
@@ -2725,10 +2743,10 @@ define_instruction(gos) {
   vt = ckoportvt(ac);
   if (vt != (cxtype_oport_t *)OPORT_STRING_NTAG &&
       vt != (cxtype_oport_t *)OPORT_BYTEVECTOR_NTAG) {
-    ac = mkeof();
+    ac = eof_obj();
   } else {
     cbuf_t *pcb = oportdata(ac);
-    ac = hpushstr(sp-r, newstring(cbdata(pcb)));
+    ac = string_obj(newstring(cbdata(pcb)));
   }
   gonexti();
 }
@@ -2737,32 +2755,32 @@ define_instruction(gos) {
 define_instruction(rdc) {
   int c; ckr(ac);
   c = iportgetc(ac);
-  if (unlikely(c == EOF)) ac = mkeof();
-  else ac = obj_from_char(c);
+  if (unlikely(c == EOF)) ac = eof_obj();
+  else ac = char_obj(c);
   gonexti();
 }
 
 define_instruction(rdac) {
   int c; ckr(ac);
   c = iportpeekc(ac);
-  if (unlikely(c == EOF)) ac = mkeof();
-  else ac = obj_from_char(c);
+  if (unlikely(c == EOF)) ac = eof_obj();
+  else ac = char_obj(c);
   gonexti();
 }
 
 define_instruction(rdcr) {
   ckr(ac);
-  ac = obj_from_bool(1); /* no portable way to detect hanging? */
+  ac = bool_obj(1); /* no portable way to detect hanging? */
   gonexti();
 }
 
 define_instruction(eofp) {
-  ac = obj_from_bool(iseof(ac));
+  ac = bool_obj(iseof(ac));
   gonexti();
 }
 
 define_instruction(eof) {
-  ac = mkeof();
+  ac = eof_obj();
   gonexti();
 }
 
@@ -2810,28 +2828,28 @@ define_instruction(wriw) {
 }
 
 define_instruction(igp) {
-  ac = obj_from_bool(isintegrable(ac));
+  ac = bool_obj(isintegrable(ac));
   gonexti(); 
 }
 
 define_instruction(iglk) {
   struct intgtab_entry *pe; cky(ac);
   pe = lookup_integrable(getsymbol(ac));
-  ac = pe ? mkintegrable(pe) : obj_from_bool(0);
+  ac = pe ? mkintegrable(pe) : bool_obj(0);
   gonexti(); 
 }
 
 define_instruction(igty) {
   int it; ckg(ac);
   it = integrable_type(integrabledata(ac));
-  ac = it ? obj_from_char(it) : obj_from_bool(0);
+  ac = it ? char_obj(it) : bool_obj(0);
   gonexti(); 
 }
 
 define_instruction(iggl) {
   const char *igs; ckg(ac);
   igs = integrable_global(integrabledata(ac));
-  ac = igs ? mksymbol(internsym((char*)igs)) : obj_from_bool(0);
+  ac = igs ? mksymbol(internsym((char*)igs)) : bool_obj(0);
   gonexti(); 
 }
 
@@ -2839,53 +2857,59 @@ define_instruction(igco) {
   int n; const char *cs; ckg(ac); ckk(sref(0));
   n = fixnum_from_obj(spop());
   cs = integrable_code(integrabledata(ac), n);
-  ac = cs ? hpushstr(sp-r, newstring((char*)cs)) : obj_from_bool(0);
+  ac = cs ? string_obj(newstring((char*)cs)) : bool_obj(0);
   gonexti(); 
 }
 
 define_instruction(rdsx) {
-  cks(ac); unload_ac(); /* ac->ra (string) */
+  cks(ac); 
+  unload_ac(); /* ac->ra (string) */
+  unload_ip(); /* ip->rx */
   hp = rds_stox(r, sp, hp);
   reload_ac(); /* ra->ac (sexp or eof) */
-  if (ac == mkeof()) fail("failed to read serialized s-expression");
+  reload_ip(); /* rx->ip */
+  if (ac == eof_obj()) fail("failed to read serialized s-expression");
   gonexti(); 
 }
 
 define_instruction(rdsc) {
   cks(ac); unload_ac(); /* ac->ra (string) */
+  unload_ac(); /* ac->ra (string) */
+  unload_ip(); /* ip->rx */
   hp = rds_stoc(r, sp, hp);
   reload_ac(); /* ra->ac (codevec or eof) */
-  if (ac == mkeof()) fail("failed to read serialized code");
+  reload_ip(); /* rx->ip */
+  if (ac == eof_obj()) fail("failed to read serialized code");
   gonexti(); 
 }
 
-define_instruction(litf) { ac = obj_from_bool(0); gonexti(); }  
-define_instruction(litt) { ac = obj_from_bool(1); gonexti(); }  
+define_instruction(litf) { ac = bool_obj(0); gonexti(); }  
+define_instruction(litt) { ac = bool_obj(1); gonexti(); }  
 define_instruction(litn) { ac = mknull(); gonexti(); }  
-define_instruction(pushlitf) { ac = obj_from_bool(0); spush(ac); gonexti(); }  
-define_instruction(pushlitt) { ac = obj_from_bool(1); spush(ac); gonexti(); }  
+define_instruction(pushlitf) { ac = bool_obj(0); spush(ac); gonexti(); }  
+define_instruction(pushlitt) { ac = bool_obj(1); spush(ac); gonexti(); }  
 define_instruction(pushlitn) { ac = mknull(); spush(ac); gonexti(); }  
 
-define_instruction(lit0) { ac = obj_from_fixnum(0); gonexti(); }  
-define_instruction(lit1) { ac = obj_from_fixnum(1); gonexti(); }  
-define_instruction(lit2) { ac = obj_from_fixnum(2); gonexti(); }  
-define_instruction(lit3) { ac = obj_from_fixnum(3); gonexti(); }  
-define_instruction(lit4) { ac = obj_from_fixnum(4); gonexti(); }  
-define_instruction(lit5) { ac = obj_from_fixnum(5); gonexti(); }  
-define_instruction(lit6) { ac = obj_from_fixnum(6); gonexti(); }  
-define_instruction(lit7) { ac = obj_from_fixnum(7); gonexti(); }  
-define_instruction(lit8) { ac = obj_from_fixnum(8); gonexti(); }  
-define_instruction(lit9) { ac = obj_from_fixnum(9); gonexti(); }  
-define_instruction(pushlit0) { ac = obj_from_fixnum(0); spush(ac); gonexti(); }  
-define_instruction(pushlit1) { ac = obj_from_fixnum(1); spush(ac); gonexti(); }  
-define_instruction(pushlit2) { ac = obj_from_fixnum(2); spush(ac); gonexti(); }  
-define_instruction(pushlit3) { ac = obj_from_fixnum(3); spush(ac); gonexti(); }  
-define_instruction(pushlit4) { ac = obj_from_fixnum(4); spush(ac); gonexti(); }  
-define_instruction(pushlit5) { ac = obj_from_fixnum(5); spush(ac); gonexti(); }  
-define_instruction(pushlit6) { ac = obj_from_fixnum(6); spush(ac); gonexti(); }  
-define_instruction(pushlit7) { ac = obj_from_fixnum(7); spush(ac); gonexti(); }  
-define_instruction(pushlit8) { ac = obj_from_fixnum(8); spush(ac); gonexti(); }  
-define_instruction(pushlit9) { ac = obj_from_fixnum(9); spush(ac); gonexti(); }  
+define_instruction(lit0) { ac = fixnum_obj(0); gonexti(); }  
+define_instruction(lit1) { ac = fixnum_obj(1); gonexti(); }  
+define_instruction(lit2) { ac = fixnum_obj(2); gonexti(); }  
+define_instruction(lit3) { ac = fixnum_obj(3); gonexti(); }  
+define_instruction(lit4) { ac = fixnum_obj(4); gonexti(); }  
+define_instruction(lit5) { ac = fixnum_obj(5); gonexti(); }  
+define_instruction(lit6) { ac = fixnum_obj(6); gonexti(); }  
+define_instruction(lit7) { ac = fixnum_obj(7); gonexti(); }  
+define_instruction(lit8) { ac = fixnum_obj(8); gonexti(); }  
+define_instruction(lit9) { ac = fixnum_obj(9); gonexti(); }  
+define_instruction(pushlit0) { ac = fixnum_obj(0); spush(ac); gonexti(); }  
+define_instruction(pushlit1) { ac = fixnum_obj(1); spush(ac); gonexti(); }  
+define_instruction(pushlit2) { ac = fixnum_obj(2); spush(ac); gonexti(); }  
+define_instruction(pushlit3) { ac = fixnum_obj(3); spush(ac); gonexti(); }  
+define_instruction(pushlit4) { ac = fixnum_obj(4); spush(ac); gonexti(); }  
+define_instruction(pushlit5) { ac = fixnum_obj(5); spush(ac); gonexti(); }  
+define_instruction(pushlit6) { ac = fixnum_obj(6); spush(ac); gonexti(); }  
+define_instruction(pushlit7) { ac = fixnum_obj(7); spush(ac); gonexti(); }  
+define_instruction(pushlit8) { ac = fixnum_obj(8); spush(ac); gonexti(); }  
+define_instruction(pushlit9) { ac = fixnum_obj(9); spush(ac); gonexti(); }  
 
 define_instruction(sref0) { ac = sref(0); gonexti(); }  
 define_instruction(sref1) { ac = sref(1); gonexti(); }  
@@ -2942,23 +2966,23 @@ define_instruction(pushdrefi3) { ac = boxref(dref(3)); spush(ac); gonexti(); }
 define_instruction(pushdrefi4) { ac = boxref(dref(4)); spush(ac); gonexti(); }
 
 define_instruction(call0) { 
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(0); 
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(0); 
   callsubi(); 
 }
 define_instruction(call1) { 
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(1); 
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(1); 
   callsubi(); 
 }
 define_instruction(call2) { 
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(2); 
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(2); 
   callsubi(); 
 }
 define_instruction(call3) { 
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(3); 
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(3); 
   callsubi(); 
 }
 define_instruction(call4) { 
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(4); 
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(4); 
   callsubi(); 
 }
 
@@ -2980,174 +3004,174 @@ define_instruction(sreturn4) {
 }
 
 define_instruction(atest0) {
-  if (unlikely(ac != obj_from_fixnum(0))) fail("argument count error on entry");
+  if (unlikely(ac != fixnum_obj(0))) fail("argument count error on entry");
   gonexti();
 }
 
 define_instruction(atest1) {
-  if (unlikely(ac != obj_from_fixnum(1))) fail("argument count error on entry");
+  if (unlikely(ac != fixnum_obj(1))) fail("argument count error on entry");
   gonexti();
 }
 
 define_instruction(atest2) {
-  if (unlikely(ac != obj_from_fixnum(2))) fail("argument count error on entry");
+  if (unlikely(ac != fixnum_obj(2))) fail("argument count error on entry");
   gonexti();
 }
 
 define_instruction(atest3) {
-  if (unlikely(ac != obj_from_fixnum(3))) fail("argument count error on entry");
+  if (unlikely(ac != fixnum_obj(3))) fail("argument count error on entry");
   gonexti();
 }
 
 define_instruction(atest4) {
-  if (unlikely(ac != obj_from_fixnum(4))) fail("argument count error on entry");
+  if (unlikely(ac != fixnum_obj(4))) fail("argument count error on entry");
   gonexti();
 }
 
 define_instruction(scall1) {
   int m = 1, n = fixnum_from_obj(*ip++);
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); 
-  ac = obj_from_fixnum(n); /* argc */
+  ckx(ac); rd = ac; rx = fixnum_obj(0); 
+  ac = fixnum_obj(n); /* argc */
   memmove((void*)(sp-n-m), (void*)(sp-n), (size_t)n*sizeof(obj));
   sdrop(m); callsubi();
 }
 
 define_instruction(scall10) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(0);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(0);
   sdrop(1); callsubi();
 }
 
 define_instruction(scall11) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(1);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(1);
   sref(1) = sref(0);
   sdrop(1); callsubi();
 }
 
 define_instruction(scall12) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(2);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(2);
   sref(2) = sref(1); sref(1) = sref(0);
   sdrop(1); callsubi();
 }
 
 define_instruction(scall13) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(3);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(3);
   sref(3) = sref(2); sref(2) = sref(1); sref(1) = sref(0);
   sdrop(1); callsubi();
 }
 
 define_instruction(scall14) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(4);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(4);
   sref(4) = sref(3); sref(3) = sref(2); sref(2) = sref(1); sref(1) = sref(0);
   sdrop(1); callsubi();
 }
 
 define_instruction(scall2) {
   int m = 2, n = fixnum_from_obj(*ip++);
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); 
-  ac = obj_from_fixnum(n);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); 
+  ac = fixnum_obj(n);
   memmove((void*)(sp-n-m), (void*)(sp-n), (size_t)n*sizeof(obj));
   sdrop(m); callsubi();
 }
 
 define_instruction(scall20) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(0);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(0);
   sdrop(2); callsubi();
 }
 
 define_instruction(scall21) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(1);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(1);
   sref(2) = sref(0);
   sdrop(2); callsubi();
 }
 
 define_instruction(scall22) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(2);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(2);
   sref(3) = sref(1); sref(2) = sref(0);
   sdrop(2); callsubi();
 }
 
 define_instruction(scall23) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(3);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(3);
   sref(4) = sref(2); sref(3) = sref(1); sref(2) = sref(0);
   sdrop(2); callsubi();
 }
 
 define_instruction(scall24) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(4);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(4);
   sref(5) = sref(3); sref(4) = sref(2); sref(3) = sref(1); sref(2) = sref(0);
   sdrop(2); callsubi();
 }
 
 define_instruction(scall3) {
   int m = 3, n = fixnum_from_obj(*ip++);
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); 
-  ac = obj_from_fixnum(n);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); 
+  ac = fixnum_obj(n);
   memmove((void*)(sp-n-m), (void*)(sp-n), (size_t)n*sizeof(obj));
   sdrop(m); callsubi();
 }
 
 define_instruction(scall30) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(0);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(0);
   sdrop(3); callsubi();
 }
 
 define_instruction(scall31) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(1);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(1);
   sref(3) = sref(0);
   sdrop(3); callsubi();
 }
 
 define_instruction(scall32) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(2);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(2);
   sref(4) = sref(1); sref(3) = sref(0);
   sdrop(3); callsubi();
 }
 
 define_instruction(scall33) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(3);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(3);
   sref(5) = sref(2); sref(4) = sref(1); sref(3) = sref(0);
   sdrop(3); callsubi();
 }
 
 define_instruction(scall34) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(4);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(4);
   sref(6) = sref(3); sref(5) = sref(2); sref(4) = sref(1); sref(3) = sref(0);
   sdrop(3); callsubi();
 }
 
 define_instruction(scall4) {
   int m = 4, n = fixnum_from_obj(*ip++);
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); 
-  ac = obj_from_fixnum(n);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); 
+  ac = fixnum_obj(n);
   memmove((void*)(sp-n-m), (void*)(sp-n), (size_t)n*sizeof(obj));
   sdrop(m); callsubi();
 }
 
 define_instruction(scall40) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(0);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(0);
   sdrop(4); callsubi();
 }
 
 define_instruction(scall41) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(1);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(1);
   sref(4) = sref(0);
   sdrop(4); callsubi();
 }
 
 define_instruction(scall42) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(2);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(2);
   sref(5) = sref(1); sref(4) = sref(0);
   sdrop(4); callsubi();
 }
 
 define_instruction(scall43) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(3);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(3);
   sref(6) = sref(2); sref(5) = sref(1); sref(4) = sref(0);
   sdrop(4); callsubi();
 }
 
 define_instruction(scall44) {
-  ckx(ac); rd = ac; rx = obj_from_fixnum(0); ac = obj_from_fixnum(4);
+  ckx(ac); rd = ac; rx = fixnum_obj(0); ac = fixnum_obj(4);
   sref(7) = sref(3); sref(6) = sref(2); sref(5) = sref(1); sref(4) = sref(0);
   sdrop(4); callsubi();
 }
@@ -3156,7 +3180,7 @@ define_instruction(brnotlt) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
     int dx = fixnum_from_obj(*ip++);
-    ac = obj_from_bool(get_fixnum_unchecked(x) < get_fixnum_unchecked(y));
+    ac = bool_obj(get_fixnum_unchecked(x) < get_fixnum_unchecked(y));
     ip = ac ? ip : ip + dx;
     gonexti(); 
   } else {
@@ -3166,7 +3190,7 @@ define_instruction(brnotlt) {
     else { cki(x); fx = (double)get_fixnum_unchecked(x); }
     if (likely(is_flonum_obj(y))) fy = flonum_from_obj(y);
     else { cki(y); fy = (double)get_fixnum_unchecked(y); }
-    ac = obj_from_bool(fx < fy);
+    ac = bool_obj(fx < fy);
     ip = ac ? ip : ip + dx;
     gonexti(); 
   }
@@ -3175,14 +3199,14 @@ define_instruction(brnotlt) {
 define_instruction(pushsub) {
   obj x = ac, y = spop();
   if (likely(are_fixnum_objs(x, y))) {
-    ac = obj_from_fixnum(fxsub(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
+    ac = fixnum_obj(fxsub(get_fixnum_unchecked(x), get_fixnum_unchecked(y)));
   } else {
     double fx, fy;
     if (likely(is_flonum_obj(x))) fx = flonum_from_obj(x);
     else { cki(x); fx = (double)get_fixnum_unchecked(x); }
     if (likely(is_flonum_obj(y))) fy = flonum_from_obj(y);
     else { cki(y); fy = (double)get_fixnum_unchecked(y); }
-    ac = obj_from_flonum(sp-r, fx - fy);
+    ac = flonum_obj(fx - fy);
   }
   spush(ac);
   gonexti(); 
@@ -3383,11 +3407,10 @@ static obj *rds_sexp(obj *r, obj *sp, obj *hp)
       if (iseof(ra)) { sdrop(1); return hp; } else spush(ra);
       ra = sref(1); hp = rds_elt(r, sp, hp); 
       if (iseof(ra)) { sdrop(2); return hp; } else spush(ra);
-      hreserve(hbsz(3), sp-r);
+      hreserve(pairbsz(), sp-r);
       *--hp = sref(0);  
       *--hp = sref(1);  
-      *--hp = obj_from_size(PAIR_BTAG); 
-      ra = hendblk(3);
+      ra = hend_pair();
       sdrop(3);      
     } break; 
     case 'l': {
@@ -3397,13 +3420,12 @@ static obj *rds_sexp(obj *r, obj *sp, obj *hp)
         ra = sref((int)i); hp = rds_elt(r, sp, hp); 
         if (iseof(ra)) { sdrop(i+1); return hp; } else spush(ra);
       }
-      hreserve(hbsz(3)*n, sp-r);
+      hreserve(pairbsz()*n, sp-r);
       ra = mknull();
       for (i = 0; i < n; ++i) {
         *--hp = ra;  
         *--hp = sref((int)i);  
-        *--hp = obj_from_size(PAIR_BTAG); 
-        ra = hendblk(3);
+        ra = hend_pair();
       }      
       sdrop(n+1);
     } break; 
@@ -3414,10 +3436,9 @@ static obj *rds_sexp(obj *r, obj *sp, obj *hp)
         ra = sref((int)i); hp = rds_elt(r, sp, hp); 
         if (iseof(ra)) { sdrop(i+1); return hp; } else spush(ra);
       }
-      hreserve(hbsz(n+1), sp-r);
+      hreserve(vecbsz(n), sp-r);
       hp -= n; memcpy(hp, sp-n, n*sizeof(obj));      
-      *--hp = obj_from_size(VECTOR_BTAG);
-      ra = hendblk(n+1);
+      ra = hend_vec(n);
       sdrop(n+1);
     } break;
     case 's': case 'y': {
@@ -3518,7 +3539,7 @@ static struct embranch *rds_prefix(obj port)
 
 static obj lastpair(obj l)
 {
-  obj p = obj_from_bool(0);
+  obj p = bool_obj(0);
   while (ispair(l)) { p = l; l = cdr(l); }
   return p;
 }
@@ -3534,10 +3555,9 @@ static fixnum_t length(obj l)
 obj *revlist2vec(obj *r, obj *sp, obj *hp)
 {
   obj l; fixnum_t n = length(ra), i;
-  hreserve(hbsz(n+1), sp-r);
+  hreserve(vecbsz(n), sp-r);
   for (l = ra, i = 0; i < n; ++i, l = cdr(l)) *--hp = car(l);
-  *--hp = obj_from_size(VECTOR_BTAG);
-  ra = hendblk(n+1);
+  ra = hend_vec(n);
   return hp;
 }
 
@@ -3546,7 +3566,7 @@ obj *close0(obj *r, obj *sp, obj *hp)
 {
   hreserve(vmclobsz(1), sp-r);
   *--hp = ra;
-  ra = hpushvmclo(1);
+  ra = hend_vmclo(1);
   return hp;
 }
 
@@ -3576,13 +3596,13 @@ static obj *rds_global_loc(obj *r, obj *sp, obj *hp)
     if (ispair(p)) ra = cdr(p);
     else { /* prepend (sym . #&sym) to *globals* */
       obj box;
-      hreserve(hbsz(2)*1+hbsz(3)*2, sp-r);
-      *--hp = ra; /* mksymbol(internsym("undefined")); */
-      *--hp = obj_from_size(BOX_BTAG); box = hendblk(2);
+      hreserve(boxbsz()*1+pairbsz()*2, sp-r);
+      *--hp = ra;
+      box = hend_box();
       *--hp = box; *--hp = ra;
-      *--hp = obj_from_size(PAIR_BTAG); ra = hendblk(3);
+      ra = hend_pair();
       *--hp = cx__2Aglobals_2A; *--hp = ra;
-      *--hp = obj_from_size(PAIR_BTAG); cx__2Aglobals_2A = hendblk(3);
+      cx__2Aglobals_2A = hend_pair();
       ra = box;
     }
   } else {
@@ -3618,9 +3638,9 @@ static obj *rds_seq(obj *r, obj *sp, obj *hp)
 more:  
   c = iportpeekc(sref(1));
   if (c == EOF) {
-    hreserve(hbsz(3), sp-r);
+    hreserve(pairbsz(), sp-r);
     *--hp = sref(0); *--hp = glue(cx_ins_2D, halt);  
-    *--hp = obj_from_size(PAIR_BTAG); ra = hendblk(3);
+    ra = hend_pair();
   } else if (c == '}') { 
     ra = sref(0);
   } else {
@@ -3632,42 +3652,42 @@ more:
       ra = mkeof();
     } else switch (pbr->etyp) {
       case 0: {
-        hreserve(hbsz(3), sp-r);
+        hreserve(pairbsz(), sp-r);
         *--hp = sref(0); *--hp = pbr->g;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         goto more;
       } break;
       case 1: {
         ra = sref(1); hp = rds_arg(r, sp, hp);
         if (iseof(ra)) goto out;
-        hreserve(hbsz(3)*2, sp-r);
+        hreserve(pairbsz()*2, sp-r);
         *--hp = sref(0); *--hp = pbr->g;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         *--hp = sref(0); *--hp = ra;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         goto more;
       } break;
       case 2: {
         ra = sref(1); hp = rds_arg(r, sp, hp);
         if (iseof(ra)) goto out;
-        hreserve(hbsz(3)*2, sp-r);
+        hreserve(pairbsz()*2, sp-r);
         *--hp = sref(0); *--hp = pbr->g;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         *--hp = sref(0); *--hp = ra;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         ra = sref(1); hp = rds_arg(r, sp, hp);
         if (iseof(ra)) goto out;
-        hreserve(hbsz(3), sp-r);
+        hreserve(pairbsz(), sp-r);
         *--hp = sref(0); *--hp = ra;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         goto more;
       } break;
       case 'f': case 't': case 'n': {
-        hreserve(hbsz(3)*2, sp-r);
+        hreserve(pairbsz()*2, sp-r);
         *--hp = sref(0); *--hp = pbr->g;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         *--hp = sref(0); *--hp = (pbr->etyp == 'n' ? mknull() : obj_from_bool(pbr->etyp == 't'));
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         goto more;
       } break;
       case 'g': { /* gref/gset */
@@ -3675,24 +3695,24 @@ more:
         if (iseof(ra)) goto out;
         hp = rds_global_loc(r, sp, hp); /* ra => ra */
         if (iseof(ra)) goto out;
-        hreserve(hbsz(3)*2, sp-r); 
+        hreserve(pairbsz()*2, sp-r); 
         *--hp = sref(0); *--hp = pbr->g;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         *--hp = sref(0); *--hp = ra;
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         goto more;
       } break;
       case 'a': { /* andbo */
-        hreserve(hbsz(3), sp-r);
+        hreserve(pairbsz(), sp-r);
         *--hp = sref(0); *--hp = pbr->g;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         c = iportpeekc(sref(1));
         if (c == EOF || c == '}') { ra = mkeof(); goto out; }
         pbr = rds_prefix(sref(1));
         if (pbr->g == 0 || pbr->etyp != 0) { ra = mkeof(); goto out; }
-        hreserve(hbsz(3), sp-r);
+        hreserve(pairbsz(), sp-r);
         *--hp = sref(0); *--hp = pbr->g;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         goto more;
       } break;
       case 's': { /* save */
@@ -3700,11 +3720,11 @@ more:
         ra = sref(1); hp = rds_block(r, sp, hp);
         if (iseof(ra)) goto out;
         n = length(ra);
-        hreserve(hbsz(3)*2, sp-r); 
+        hreserve(pairbsz()*2, sp-r); 
         *--hp = sref(0); *--hp = pbr->g;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         *--hp = sref(0); *--hp = obj_from_fixnum(n);
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         if (n > 0) {
           obj lp = lastpair(ra); assert(ispair(lp));
           cdr(lp) = sref(0); sref(0) = ra;
@@ -3720,13 +3740,13 @@ more:
         if (iseof(ra)) goto out;
         hp = revlist2vec(r, sp, hp); /* ra => ra */
         if (iseof(ra)) goto out;
-        hreserve(hbsz(3)*3, sp-r); 
+        hreserve(pairbsz()*3, sp-r); 
         *--hp = sref(0); *--hp = pbr->g;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         *--hp = sref(0); *--hp = obj_from_fixnum(n);
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         *--hp = sref(0); *--hp = ra;  
-        *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+        sref(0) = hend_pair();
         goto more;
       } break;
       case 'b': { /* branches */
@@ -3739,33 +3759,33 @@ more:
           spush(bseq1); /* ... port, l, bseq1 <= sp */
           ra = sref(2); hp = rds_block(r, sp, hp);
           if (iseof(ra)) { sdrop(1); goto out; }
-          hreserve(hbsz(3)*4, sp-r); 
+          hreserve(pairbsz()*4, sp-r); 
           bseq1 = spop(); bseq2 = ra;
           n = length(bseq1);
           *--hp = sref(0); *--hp = pbr->g;  
-          *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+          sref(0) = hend_pair();
           *--hp = sref(0); *--hp = obj_from_fixnum(n+2);
-          *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+          sref(0) = hend_pair();
           if (n > 0) {
             obj lp = lastpair(bseq1); assert(ispair(lp));
             cdr(lp) = sref(0); sref(0) = bseq1;
           }
           *--hp = sref(0); *--hp = glue(cx_ins_2D, br);
-          *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+          sref(0) = hend_pair();
           n = length(bseq2);
           *--hp = sref(0); *--hp = obj_from_fixnum(n);
-          *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+          sref(0) = hend_pair();
           if (n > 0) {
             obj lp = lastpair(bseq2); assert(ispair(lp));
             cdr(lp) = sref(0); sref(0) = bseq2;
           }
         } else { /* regular 1-arm branch */
           n = length(ra);
-          hreserve(hbsz(3)*2, sp-r); 
+          hreserve(pairbsz()*2, sp-r); 
           *--hp = sref(0); *--hp = pbr->g;  
-          *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+          sref(0) = hend_pair();
           *--hp = sref(0); *--hp = obj_from_fixnum(n);
-          *--hp = obj_from_size(PAIR_BTAG); sref(0) = hendblk(3);
+          sref(0) = hend_pair();
           if (n > 0) {
             obj lp = lastpair(ra); assert(ispair(lp));
             cdr(lp) = sref(0); sref(0) = ra;
@@ -3930,11 +3950,11 @@ static obj *init_module(obj *r, obj *sp, obj *hp, const char **mod)
       /* or add new binding */
       spush(oldden); /* protect from gc */
       if (!bnd) { /* acons (sym . #f) */
-        hreserve(hbsz(3)*2, sp-r);
+        hreserve(pairbsz()*2, sp-r);
         *--hp = obj_from_bool(0); *--hp = sym;
-        *--hp = obj_from_size(PAIR_BTAG); bnd = hendblk(3);
+        bnd = hend_pair();
         *--hp = cx__2Atransformers_2A; *--hp = bnd;
-        *--hp = obj_from_size(PAIR_BTAG); cx__2Atransformers_2A = hendblk(3);
+        cx__2Atransformers_2A = hend_pair();
       }
       cdr(bnd) = spop(); /* oldden */
       continue;    
@@ -3953,11 +3973,11 @@ static obj *init_module(obj *r, obj *sp, obj *hp, const char **mod)
       }
       /* or add new binding */
       if (bnd == mknull()) { /* acons (sym . #f) */
-        hreserve(hbsz(3)*2, sp-r);
+        hreserve(pairbsz()*2, sp-r);
         *--hp = obj_from_bool(0); *--hp = sym;
-        *--hp = obj_from_size(PAIR_BTAG); bnd = hendblk(3);
+        bnd = hend_pair();
         *--hp = cx__2Atransformers_2A; *--hp = bnd;
-        *--hp = obj_from_size(PAIR_BTAG); cx__2Atransformers_2A = hendblk(3);
+        cx__2Atransformers_2A = hend_pair();
       }
       /* sexp-decode data into the cdr of the binding */
       spush(bnd); /* protect from gc */
diff --git a/src/s.scm b/src/s.scm
index f0c5aee..d51e8a0 100644
--- a/src/s.scm
+++ b/src/s.scm
@@ -861,6 +861,8 @@
 
 (define-syntax call-with-current-continuation call/cc)
 
+;dynamic-wind
+
 (define (%map1 p l)
   (let loop ([l l] [r '()])
     (if (pair? l) 
@@ -945,6 +947,35 @@
       (apply for-each p (map vector->list (cons v v*)))))
 
 
+;---------------------------------------------------------------------------------------------
+; Exceptions
+;---------------------------------------------------------------------------------------------
+
+;TBD:
+;
+;with-exception-handler
+;raise
+;raise-continuable
+;error
+;error-object?
+;error-object-message
+;error-object-irritants
+;read-error?
+;file-error?
+
+;---------------------------------------------------------------------------------------------
+; Environments and evaluation
+;---------------------------------------------------------------------------------------------
+
+;TBD:
+;
+;environment
+;scheme-report-environment
+;null-environment
+;interaction-environment
+;eval
+
+
 ;---------------------------------------------------------------------------------------------
 ; I/O Ports
 ;---------------------------------------------------------------------------------------------