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forth: Add "DO" and "LOOP"

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Also, un-IMMEDIATE "LITN" it didn't make any sense.
This commit is contained in:
Virgil Dupras 2020-03-18 20:04:44 -04:00
parent 587d1d0d69
commit d874f20278
3 changed files with 21 additions and 6 deletions
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23
apps/forth/core.fs
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@ -3,7 +3,7 @@
: +! SWAP OVER @ + SWAP ! ;
: ALLOT HERE +! ;
: C, H C! 1 ALLOT ;
: COMPILE ' ['] LITN EXECUTE ['] , , ; IMMEDIATE
: COMPILE ' LITN ['] , , ; IMMEDIATE
: BEGIN H ; IMMEDIATE
: AGAIN COMPILE (bbr) H -^ C, ; IMMEDIATE
: UNTIL COMPILE SKIP? COMPILE (bbr) H -^ C, ; IMMEDIATE
@ -15,9 +15,7 @@
input buffer size in Collapse OS
COMPILE; Tough one. Get addr of caller word (example above
(bbr)) and then call LITN on it. However, LITN is an
immediate and has to be indirectly executed. Then, write
a reference to "," so that this word is written to HERE.
(bbr)) and then call LITN on it.
NOT: a bit convulted because we don't have IF yet )
@ -49,3 +47,20 @@
: > 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

2
apps/forth/dict.asm
View File

@ -444,7 +444,7 @@ ISIMMED:
.db "LITN"
.fill 3
.dw ISIMMED
.db 1 ; IMMEDIATE
.db 0
LITN:
.dw nativeWord
ld hl, (HERE)

2
apps/forth/dictionary.txt
View File

@ -50,7 +50,7 @@ CONSTANT x n -- Creates cell x that when called pushes its value
DOES> -- See description at top of file
IMMED? a -- f Checks whether wordref at a is immediate.
IMMEDIATE -- Flag the latest defined word as immediate.
LITN n -- *I* Inserts number from TOS as a literal
LITN n -- Write number n as a literal.
VARIABLE c -- Creates cell x with 2 bytes allocation.
Compilation vs meta-compilation. When you compile a word with "[COMPILE] foo",