collapseos/apps/forth/core.fs
Virgil Dupras d874f20278 forth: Add "DO" and "LOOP"
Also, un-IMMEDIATE "LITN" it didn't make any sense.
2020-03-18 20:04:44 -04:00

67 lines
1.8 KiB
Forth

: H HERE @ ;
: -^ SWAP - ;
: +! SWAP OVER @ + SWAP ! ;
: ALLOT HERE +! ;
: C, H C! 1 ALLOT ;
: COMPILE ' LITN ['] , , ; IMMEDIATE
: BEGIN H ; IMMEDIATE
: AGAIN COMPILE (bbr) H -^ C, ; IMMEDIATE
: UNTIL COMPILE SKIP? COMPILE (bbr) H -^ C, ; IMMEDIATE
: NOT 1 SWAP SKIP? EXIT 0 * ;
: ( BEGIN LITS ) WORD SCMP NOT UNTIL ; IMMEDIATE
( Hello, hello, krkrkrkr... do you hear me?
Ah, voice at last! Some lines above need comments
BTW: Forth lines limited to 64 cols because of default
input buffer size in Collapse OS
COMPILE; Tough one. Get addr of caller word (example above
(bbr)) and then call LITN on it.
NOT: a bit convulted because we don't have IF yet )
: IF ( -- a | a: br cell addr )
COMPILE SKIP? ( if true, don't branch )
COMPILE (fbr)
H ( push a )
1 ALLOT ( br cell allot )
; IMMEDIATE
: THEN ( a -- | a: br cell addr )
DUP H -^ SWAP ( a-H a )
C!
; IMMEDIATE
: ELSE ( a1 -- a2 | a1: IF cell a2: ELSE cell )
COMPILE (fbr)
1 ALLOT
DUP H -^ SWAP ( a-H a )
C!
H 1 - ( push a. -1 for allot offset )
; IMMEDIATE
: ? @ . ;
: VARIABLE CREATE 2 ALLOT ;
: CONSTANT CREATE H ! DOES> @ ;
: = CMP NOT ;
: < CMP 0 1 - = ;
: > CMP 1 = ;
: / /MOD SWAP DROP ;
: MOD /MOD DROP ;
( In addition to pushing H this compiles 2 >R so that loop variables are sent
to PS at runtime )
: DO
COMPILE SWAP COMPILE >R COMPILE >R
H
; IMMEDIATE
( One could think that we should have a sub word to avoid all these COMPILE,
but we can't because otherwise it messes with the RS )
: LOOP
COMPILE R> 1 LITN COMPILE + COMPILE DUP COMPILE >R
COMPILE I' COMPILE = COMPILE SKIP? COMPILE (bbr)
H -^ C,
COMPILE R> COMPILE DROP COMPILE R> COMPILE DROP
; IMMEDIATE