Demonstrate that the Rust file fits in 500 lines after stripping comments

frustration_minimal.rs

@@ -0,0 +1,500 @@
+// This is equivalent to frustration.rs but with comments stripped.
+// Line count: 500
+
+use std::convert::TryInto;
+use std::io;
+use std::io::Read;
+use std::io::Write;
+
+const ADDRESS_SPACE: usize = 65536;
+
+#[derive(Debug)]
+struct Stack<const N: usize> {
+    mem: [u16; N],
+    tos: usize  /* top-of-stack */
+}
+
+impl<const N: usize> Stack<N> {
+    fn push(&mut self, val: u16) {
+        self.tos = (self.tos.wrapping_add(1)) & (N - 1);
+        self.mem[self.tos] = val;
+    }
+
+    fn pop(&mut self) -> u16 {
+        let val = self.mem[self.tos];
+        self.mem[self.tos] = 0;
+        self.tos = (self.tos.wrapping_sub(1)) & (N - 1);
+        return val;
+    }
+
+    fn new() -> Stack<N> {
+        return Stack {tos: N-1, mem: [0; N]};
+    }
+}
+
+struct Core {
+    ram: [u8; ADDRESS_SPACE],
+    ip: u16,
+    dstack: Stack<16>,
+    rstack: Stack<32>
+}
+
+impl Core {
+    fn new() -> Core {
+        return Core {
+            ram: [0; ADDRESS_SPACE],
+            ip: 0,
+            dstack: Stack::new(),
+            rstack: Stack::new()}
+    }
+
+    fn load(&self, addr: u16) -> u16 {
+        let a = addr as usize;
+        return u16::from_le_bytes(self.ram[a..=a+1].try_into().unwrap());
+    }
+
+
+    fn store(&mut self, addr: u16, val: u16) {
+        let a = addr as usize;
+        self.ram[a..=a+1].copy_from_slice(&val.to_le_bytes());
+    }
+
+    fn step(&mut self) {
+        let opcode = self.load(self.ip);
+        self.ip = self.ip.wrapping_add(2);
+
+        if (opcode >= 0xffe0) && (opcode & 1 == 0) {
+            PRIMITIVES[((opcode - 0xffe0) >> 1) as usize](self);
+        }
+        else if (opcode & 1) == 1 {
+            self.dstack.push(opcode >> 1);
+        }
+        else {
+            self.rstack.push(self.ip);
+            self.ip = opcode;
+        }
+    }
+}
+
+enum Op {
+    RET = 0xffe0, TOR = 0xffe2, RTO = 0xffe4, LD  = 0xffe6,
+    ST  = 0xffe8, DUP = 0xffea, SWP = 0xffec, DRP = 0xffee,
+    Q   = 0xfff0, ADD = 0xfff2, SFT = 0xfff4, OR  = 0xfff6,
+    AND = 0xfff8, INV = 0xfffa, GEQ = 0xfffc, IO  = 0xfffe,
+}
+
+type Primitive = fn(&mut Core);
+
+const PRIMITIVES: [Primitive; 16] = [
+    | x | {
+        /* RET - Return from subroutine */
+        x.ip = x.rstack.pop()
+    },
+    | x | {
+        /* TOR - Transfer number from data stack to return stack */
+        x.rstack.push(x.dstack.pop())
+    },
+    | x | {
+        /* RTO - Transfer number from return stack to data stack */
+        x.dstack.push(x.rstack.pop())
+    },
+    | x | {
+        /* LD - Load number from memory address specified on the data stack */
+        let a = x.dstack.pop();
+        x.dstack.push(x.load(a));
+    },
+    | x | {
+        /* ST - Store number to memory address specified on the data stack */
+        let a = x.dstack.pop();
+        let v = x.dstack.pop();
+        x.store(a, v);
+    },
+    | x | {
+        /* DUP - Duplicate the top number on the data stack */
+        let v = x.dstack.pop();
+        x.dstack.push(v);
+        x.dstack.push(v);
+    },
+    | x | {
+        /* SWP - Exchange the top two numbers on the data stack */
+        let v1 = x.dstack.pop();
+        let v2 = x.dstack.pop();
+        x.dstack.push(v1);
+        x.dstack.push(v2);
+    },
+    | x | {
+        /* DRP - Discard the top number on the data stack */
+        let _ = x.dstack.pop();
+    },
+    | x | {
+        /* Q - If the top number on the data stack is zero, skip the next
+         * instruction. */
+        let f = x.dstack.pop();
+        if f == 0 {
+            x.ip = x.ip.wrapping_add(2)
+        }
+    },
+    | x | {
+        /* ADD - Sum the top two numbers on the data stack. */
+        let v1 = x.dstack.pop();
+        let v2 = x.dstack.pop();
+        x.dstack.push(v1.wrapping_add(v2));
+    },
+    | x | {
+        /* SFT - Bit shift number left or right by the specified amount.
+         * A positive shift amount shifts left, negative shifts right. */
+        let amt = x.dstack.pop();
+        let val = x.dstack.pop();
+        x.dstack.push(
+            if amt <= 0xf {
+                val << amt
+            } else if amt >= 0xfff0 {
+                val >> (0xffff - amt + 1)
+            } else {
+                0
+            }
+        );
+    },
+    | x | { // OR - Bitwise-or the top two numbers on the data stack.
+        let v1 = x.dstack.pop();
+        let v2 = x.dstack.pop();
+        x.dstack.push(v1 | v2);
+    },
+    | x | { // AND - Bitwise-and the top two numbers on the data stack.
+        let v1 = x.dstack.pop();
+        let v2 = x.dstack.pop();
+        x.dstack.push(v1 & v2);
+    },
+    | x | { // INV - Bitwise-invert the top number on the data stack.
+        let v1 = x.dstack.pop();
+        x.dstack.push(!v1);
+    },
+    | x | { // GEQ - Unsigned-compare the top two items on the data stack.
+        let v2 = x.dstack.pop();
+        let v1 = x.dstack.pop();
+        x.dstack.push(if v1 >= v2 { 0xffff } else { 0 });
+    },
+    | x | { // IO - Write/read a number from/to input/output port.
+        let port = x.dstack.pop();
+        match port {
+            0 => { /* Push a character from stdin onto the data stack */
+                let mut buf: [u8; 1] = [0];
+                let _ = io::stdin().read(&mut buf);
+                x.dstack.push(buf[0] as u16);
+            }
+            1 => { /* Pop a character from the data stack to stdout */
+                let val  = x.dstack.pop();
+                print!("{}", ((val & 0xff) as u8) as char);
+                let _ = io::stdout().flush();
+            }
+            2 => { /* Dump CPU status. */
+                println!("{:?} {:?}", x.ip, x.dstack);
+                let _ = io::stdout().flush();
+            }
+            _ => {}
+        }
+    }
+];
+
+struct Dict<'a> {
+    dp: u16,
+    here: u16,
+    c: &'a mut Core
+}
+
+enum Item {
+    Literal(u16),
+    Call(u16),
+    Opcode(Op)
+}
+impl From<u16> for Item { fn from(a: u16) -> Self { Item::Call(a) } }
+impl From<Op>  for Item { fn from(o: Op)  -> Self { Item::Opcode(o) } }
+
+impl Dict<'_> {
+    fn allot(&mut self, n: u16) {
+        self.here = self.here.wrapping_add(n);
+    }
+
+    fn comma(&mut self, val: u16) {
+        self.c.store(self.here, val);
+        self.allot(2);
+    }
+
+    fn emit<T: Into<Item>>(&mut self, val: T) {
+        match val.into() {
+            Item::Call(val)    => { self.comma(val) }
+            Item::Opcode(val)  => { self.comma(val as u16) }
+            Item::Literal(val) => { assert!(val <= 0x7fff);
+                                    self.comma((val << 1) | 1) }
+        }
+    }
+
+    fn name(&mut self, n: u8, val: [u8; 3]) {
+        self.comma(n as u16 | ((val[0] as u16) << 8));
+        self.comma(val[1] as u16 | ((val[2] as u16) << 8));
+    }
+
+    fn entry(&mut self) {
+        let here = self.here;
+        self.comma(self.dp);
+        self.dp = here;
+    }
+}
+
+fn build_dictionary(c: &mut Core) {
+    use Op::*;
+    use Item::*;
+
+    let mut d = Dict { dp: 0, here: 2, c: c };
+
+    macro_rules! forth {
+        ($x:expr) => (d.emit($x));
+        ($x:expr, $($y:expr),+) => (d.emit($x); forth!($($y),+))
+    }
+
+    // key ( -- n )
+    d.entry(); d.name(3, *b"key"); let key = d.here;
+    forth!(Literal(0), IO, RET);
+
+    // emit ( n -- )
+    d.entry(); d.name(4, *b"emi");  let emit = d.here;
+    forth!(Literal(1), IO, RET);
+
+    // - ( a b -- a-b )
+    d.entry(); d.name(1, *b"-  ");  let sub = d.here;
+    forth!(INV, Literal(1), ADD, ADD, RET);
+
+    let zero = d.here;
+    forth!(Literal(0), RTO, DRP, RET);
+
+    // 0= ( n -- f )
+    d.entry(); d.name(2, *b"0= ");  let zero_eq = d.here;
+    forth!(Q, zero, Literal(0), INV, RET);
+
+    // = ( a b -- a=b )
+    d.entry(); d.name(1, *b"=  ");  let eq = d.here;
+    forth!(sub, zero_eq, RET);
+
+    let skip_helper = d.here;
+    forth!(RTO, DRP, key, DUP, Literal(33), GEQ, Q, RET, DRP, skip_helper);
+
+    // skipws ( -- c )
+    d.entry(); d.name(6, *b"ski");  let skipws = d.here;
+    forth!(skip_helper);
+
+    // over ( a b -- a b a )
+    d.entry(); d.name(4, *b"ove");  let over = d.here;
+    forth!(TOR, DUP, RTO, SWP, RET);
+
+    // 2dup ( a b -- a b a b )
+    d.entry(); d.name(4, *b"2du");  let twodup = d.here;
+    forth!(over, over, RET);
+
+    let word_buf = d.here;
+    d.allot(6);
+
+    // min ( a b -- n )
+    d.entry(); d.name(3, *b"min");  let min = d.here;
+    forth!(twodup, GEQ, Q, SWP, DRP, RET);
+
+    // c@ ( a -- n )
+    d.entry(); d.name(2, *b"c@ ");  let cld = d.here;
+    forth!(LD, Literal(0xff), AND, RET);
+
+    // c! ( n a -- )
+    d.entry(); d.name(2, *b"c! ");  let cst = d.here;
+    forth!(DUP, LD, Literal(0xff), INV, AND, SWP, TOR, OR, RTO, ST, RET);
+
+    // Load 1 letter into the buffer.
+    let stchar = d.here;
+    forth!(
+        Literal(word_buf), cld, Literal(1), ADD, DUP, Literal(word_buf), cst,
+        Literal(5), min, Literal(word_buf), ADD, cst, RET);
+
+    let getcs_helper = d.here;
+    forth!(RTO, DRP, stchar, key, DUP, Literal(32), SWP, GEQ, Q, RET,
+           getcs_helper);
+
+    // getcs ( -- c )
+    d.entry(); d.name(5, *b"get");  let getcs = d.here;
+    forth!(getcs_helper, RET);
+
+    // word ( -- )
+    d.entry(); d.name(4, *b"wor");  let word = d.here;
+    forth!(Literal(word_buf),
+           DUP, Literal(2), ADD,
+           Literal(0x2020), SWP, ST,
+           Literal(0x2000), SWP, ST,
+           skipws, getcs, DRP, RET);
+
+    // latest ( -- a )
+    let latest_ptr = d.here; d.allot(2);
+    d.entry(); d.name(6, *b"lat");  let latest = d.here;
+    forth!(Literal(latest_ptr), RET);
+
+    // Helper word ( a -- f )
+    let matches = d.here;
+    forth!(Literal(2), ADD, TOR,
+           Literal(word_buf), DUP, Literal(2), ADD, LD, SWP, LD,
+           RTO, DUP, TOR, LD, Literal(0x0080), INV, AND, eq,
+           SWP, RTO, Literal(2), ADD, LD, eq, AND, RET);
+
+    // Helper word ( a -- a' )
+    let matched = d.here;
+    forth!(Literal(6), ADD, RTO, DRP, RET);
+
+    let find_helper = d.here;
+    forth!(RTO, DRP,
+           DUP, Literal(0), eq, Q, RET, /* No match - return 0 */
+           DUP, matches, Q, matched,    /* Match - return the code address */
+           LD, find_helper);            /* Try the next one */
+
+    // find ( -- xt|0 )
+    d.entry(); d.name(4, *b"fin");  let find = d.here;
+    forth!(latest, LD, find_helper);
+
+    // ' ( -- xt|0 )
+    d.entry(); d.name(1, *b"'  ");  let quote = d.here;
+    forth!(word, find, RET);
+
+    // here ( -- a )
+    let here_ptr = d.here; d.allot(2);
+    d.entry(); d.name(4, *b"her");  let here = d.here;
+    forth!(Literal(here_ptr), RET);
+
+    // state ( -- a )
+    let state_ptr = d.here; d.allot(2);
+    d.entry(); d.name(5, *b"sta");  let state = d.here;
+    forth!(Literal(state_ptr), RET);
+
+    let word_addr = d.here;
+    forth!(Literal(latest_ptr), LD, Literal(2), ADD, RET);
+
+    // immediate ( -- )
+    d.entry(); d.name(9, *b"imm");
+    forth!(word_addr, DUP, LD, Literal(0x0080), OR, SWP, ST, RET);
+
+    // [ ( -- )
+    d.entry(); d.name(1 | 0x80, *b"[  ");
+    let lbracket = d.here;
+    forth!(Literal(0), INV, state, ST, RET);
+
+    // ] ( -- )
+    d.entry(); d.name(1 | 0x80, *b"]  ");  let rbracket = d.here;
+    forth!(Literal(0), state, ST, RET);
+
+    // smudge ( -- )
+    d.entry(); d.name(6 | 0x80, *b"smu");  let smudge = d.here;
+    forth!(word_addr, DUP, LD, Literal(0x0040), OR, SWP, ST, RET);
+
+    // unsmudge ( -- )
+    d.entry(); d.name(8 | 0x80, *b"uns");  let unsmudge = d.here;
+    forth!(word_addr, DUP, LD, Literal(0x0040), INV, AND, SWP, ST, RET);
+
+    // , ( n -- )
+    d.entry(); d.name(1, *b",  "); let comma = d.here;
+    forth!(here, LD, ST,
+           here, LD, Literal(2), ADD, here, ST, RET);
+
+    // x10 ( n -- n*10 )
+    d.entry(); d.name(3, *b"x10");  let x10 = d.here;
+    forth!(DUP, DUP, Literal(3), SFT, ADD, ADD, RET);
+
+    let end_num = d.here;
+    forth!(DRP, RTO, DRP, RET);
+
+    let bad_num = d.here;
+    forth!(DRP, DRP, DRP, Literal(0), INV, RTO, DRP, RET);
+
+    // Helper function ( 0 1 -- n|-1 )
+    let number_helper = d.here;
+    forth!(RTO, DRP,
+           DUP, Literal(word_buf), ADD, cld,
+           Literal(48), sub, DUP, Literal(10), GEQ, Q, bad_num,
+           SWP, TOR, SWP, x10, ADD, RTO,
+           DUP, Literal(word_buf), cld, GEQ, Q, end_num,
+           Literal(1), ADD, number_helper);
+
+    // number ( -- n|-1 )
+    d.entry(); d.name(6, *b"num");  let number = d.here;
+    forth!(Literal(0), Literal(1), number_helper);
+
+    // lit ( n -- )
+    d.entry(); d.name(3, *b"lit");  let lit = d.here;
+    forth!(DUP, ADD, Literal(1), ADD, comma, RET);
+
+    // Helper function to compile a number ( n -- n? )
+    let try_compile_lit = d.here;
+    forth!(state, LD, Q, RET, lit, RTO, DRP, RET);
+
+    // Helper function to compile a call ( xt -- xt? )
+    let try_compile_call = d.here;
+    forth!(
+        DUP, Literal(4), sub, LD, Literal(0x0080), AND, state, LD, OR, Q, RET,
+        comma, RTO, DRP, RET);
+
+    // execute ( xt -- )
+    d.entry(); d.name(7, *b"exe");  let execute = d.here;
+    forth!(TOR, RET);
+
+    // Helper function to compile or execute a word ( xt -- )
+    let do_word = d.here;
+    forth!(RTO, DRP, try_compile_call, execute, RET);
+
+    let bad = d.here;
+    forth!(DRP, Literal(63), emit, RTO, DRP, RET);
+
+    // dispatch ( xt -- )
+    d.entry(); d.name(9, *b"int");  let dispatch = d.here;
+    forth!(DUP, Q, do_word,
+           DRP, number, DUP, Literal(1), ADD, zero_eq, Q, bad,
+           try_compile_lit, RET);
+
+    // quit ( -- )
+    d.entry(); d.name(4, *b"qui");  let quit = d.here;
+    forth!(quote, dispatch, quit);
+
+    // create ( -- )
+    d.entry(); d.name(6, *b"cre");  let create = d.here;
+    forth!(
+        here, LD, latest, LD, comma, latest, ST, word,
+        Literal(word_buf), DUP, LD, comma, Literal(2), ADD, LD, comma, RET);
+
+    // : ( -- )
+    d.entry(); d.name(1, *b":  ");
+    forth!(create, smudge, rbracket, RET);
+
+    // ; ( -- )
+    d.entry(); d.name(1 | 0x80, *b";  ");
+    forth!(Literal(!(RET as u16)), INV, comma, unsmudge, lbracket, RET);
+
+    d.entry(); d.name(3, *b"ret"); forth!(RTO, DRP, RET);
+    d.entry(); d.name(2, *b">r "); forth!(RTO, SWP, TOR, TOR, RET);
+    d.entry(); d.name(2, *b"r> "); forth!(RTO, RTO, SWP, TOR, RET);
+    d.entry(); d.name(1, *b"@  "); forth!(LD, RET);
+    d.entry(); d.name(1, *b"!  "); forth!(ST, RET);
+    d.entry(); d.name(3, *b"dup"); forth!(DUP, RET);
+    d.entry(); d.name(4, *b"swa"); forth!(SWP, RET);
+    d.entry(); d.name(4, *b"dro"); forth!(DRP, RET);
+    d.entry(); d.name(1 | 0x80, *b"?  "); /* This one only works in-line. */
+    forth!(Literal(!(Q as u16)), INV, comma, RET);
+    d.entry(); d.name(1, *b"+  "); forth!(ADD, RET);
+    d.entry(); d.name(5, *b"shi"); forth!(SFT, RET);
+    d.entry(); d.name(2, *b"or "); forth!(OR, RET);
+    d.entry(); d.name(3, *b"and"); forth!(AND, RET);
+    d.entry(); d.name(3, *b"inv"); forth!(INV, RET);
+    d.entry(); d.name(3, *b"u>="); forth!(GEQ, RET);
+    d.entry(); d.name(2, *b"io "); forth!(IO, RET);
+
+    d.c.store(latest_ptr, d.dp);
+    d.c.store(here_ptr, d.here);
+    d.c.store(state_ptr, 0xffff);
+    d.c.store(0, quit);
+}
+
+fn main() {
+    let mut c = Core::new();
+    build_dictionary(&mut c);
+    c.ip = 0;
+    loop { c.step(); }
+}