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forth: separate COMPILE and [COMPILE]

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This commit is contained in:
Virgil Dupras 2020-03-16 21:31:43 -04:00
parent f404c2f4d0
commit aec98a7a3a
3 changed files with 29 additions and 8 deletions
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18
apps/forth/core.fs
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@ -5,22 +5,28 @@
: , H ! 2 ALLOT ;
: C, H C! 1 ALLOT ;
: BEGIN H ; IMMEDIATE
: AGAIN ['] (bbr) , H -^ C, ; IMMEDIATE
: COMPILE ' ['] LITN EXECUTE ['] , , ; IMMEDIATE
: AGAIN COMPILE (bbr) H -^ C, ; IMMEDIATE
: NOT 1 SWAP SKIP? EXIT 0 * ;
: ( BEGIN LITS ) WORD SCMP NOT SKIP? AGAIN ; 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
NOT: a bit convulted because we don't have IF yet
IF true, skip following (fbr). Also, push br cell ref H,
to PS )
: IF ['] SKIP? , ['] (fbr) , H 1 ALLOT ; IMMEDIATE
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.
NOT: a bit convulted because we don't have IF yet )
: IF COMPILE SKIP? COMPILE (fbr) H 1 ALLOT ; IMMEDIATE
( Subtract TOS from H to get offset to write to IF or ELSE's
br cell )
: THEN DUP H -^ SWAP C! ; IMMEDIATE
( write (fbr) addr, allot, then same as THEN )
: ELSE ['] (fbr) , 1 ALLOT DUP H -^ SWAP C! H 1 - ; IMMEDIATE
: ELSE
COMPILE (fbr) 1 ALLOT DUP H -^ SWAP C! H 1 - ; IMMEDIATE
: ? @ . ;
: VARIABLE CREATE 2 ALLOT ;
: CONSTANT CREATE H ! DOES> @ ;

2
apps/forth/dict.asm
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@ -225,7 +225,7 @@ EXECUTE:
jp (hl) ; go!
.db "COMPILE"
.db "[COMPIL"
.dw EXECUTE
.db 1 ; IMMEDIATE
COMPILE:

17
apps/forth/dictionary.txt
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@ -42,13 +42,28 @@ directly, but as part of another word.
ALLOT n -- Move HERE by n bytes
C, b -- Write byte b in HERE and advance it.
CREATE x -- Create cell named x. Doesn't allocate a PF.
COMPILE x -- Compile word x and write it to HERE
[COMPILE] x -- Compile word x and write it to HERE
COMPILE x -- Meta compiles. Kind of blows the mind. See below.
CONSTANT x n -- Creates cell x that when called pushes its value
DOES> -- See description at top of file
IMMEDIATE -- Flag the latest defined word as immediate.
LITN n -- *I* Inserts number from TOS as a literal
VARIABLE c -- Creates cell x with 2 bytes allocation.
Compilation vs meta-compilation. When you compile a word with "[COMPILE] foo",
its straightforward: It writes down to HERE wither the address of the word or
a number literal.
When you *meta* compile, it's a bit more mind blowing. It fetches the address
of the word specified by the caller, then writes that number as a literal,
followed by a reference to ",".
Example: ": foo [COMPILE] bar;" is the equivalent of ": foo bar ;" if bar is
not an immediate. However, ": foo COMPILE bar ;" is the equivalent of
": foo ['] bar , ;". Got it?
Meta-compile only works with real words, not number literals.
*** Flow ***
Note about flow words: flow words can only be used in definitions. In the
INTERPRET loop, they don't have the desired effect because each word from the