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Fix LOOP/+LOOP bug.

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Forth-83 and after pick a more useful definition of how
LOOP and +LOOP should decide termination:
if the last step traversed between limit-1 and limit.

This allows for signed or unsigned loops with the same construct.

Updating to this behavior + adding test + fixing old test
that didn't match gforth.
This commit is contained in:
Brad Nelson
2023-05-05 00:46:18 -07:00
parent 705e839c62
commit bab72b79a7
2 changed files with 63 additions and 50 deletions
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6
common/boot.fs
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@ -69,10 +69,12 @@ variable leaving
: UNLOOP r> rdrop rdrop >r ;
: LEAVE r> rdrop rdrop @ >r ;
: leave postpone LEAVE leaving, ; immediate
: +LOOP ( n -- ) dup 0< swap r> r> rot + dup r@ < -rot >r >r xor 0=
: +LOOP ( n -- ) r> r> dup r@ - >r rot + r> -rot
dup r@ - -rot >r >r xor 0<
if r> cell+ rdrop rdrop >r else r> @ >r then ;
: +loop ( n -- ) postpone +LOOP , )leaving ; immediate
: LOOP r> r> 1+ dup r@ < -rot >r >r 0=
: LOOP r> r> dup r@ - >r 1+ r> -rot
dup r@ - -rot >r >r xor 0<
if r> cell+ rdrop rdrop >r else r> @ >r then ;
: loop postpone LOOP , )leaving ; immediate
create I ' r@ @ ' i ! ( i is same as r@ )