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Add [if]..[else]..[then]

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Koichi Nakamura 2021-01-05 09:19:04 +09:00
parent f1b92c39d7
commit 9af496fd66
1 changed files with 42 additions and 0 deletions
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42
bootstrap.fs
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@ -461,6 +461,7 @@ alias-builtin xor ^
: c, B ;
: cmove, m ;
: strlen z ;
: str= E ;
: state M ;
: aligned a ;
: align A ;
@ -1643,4 +1644,45 @@ stdin_ push-inputstream
switch-to-4th-stage
( === [if]..[else]..[then] === )
: [if] ( f -- )
unless
\ skip inputs until corresponding [else] or [then]
0 \ depth
begin
word throw
dup s" [if]" str= if
drop 1+
else dup s" [else]" str= if
drop
dup 0= if drop exit then
else s" [then]" str= if
dup 0= if drop exit then
1-
then then then
again
then
; immediate
: [else]
\ If the condition is false, [else] is skipped by [if].
\ So when the execution reaches [else] it means that
\ the condition was true.
\ skip inputs until corresponding [then]
0 \ depth
begin
word throw
dup s" [if]" str= if
drop 1+
else s" [then]" str= if
dup 0= if drop exit then
1-
then then
again
; immediate
: [then] ; immediate \ do nothing
." Ready" cr