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collapseos/apps/forth/core.fth
Virgil Dupras 7befe56597 forth: improve input flow
Readline, instead of being triggered by the end of execution of the last
compiled line is now triggered "just in time", by "WORD".

This allows IMMEDIATE words reading input buffer to span multiple lines
( comments for example, but colon definitions will soon follow ).
2020-03-14 19:10:39 -04:00

31 lines
1.0 KiB
Forth

: H HERE @ ;
: -^ SWAP - ;
: +! SWAP OVER @ + SWAP ! ;
: ALLOT HERE +! ;
: , H ! 2 ALLOT ;
: C, H C! 1 ALLOT ;
: NOT 1 SWAP SKIP? EXIT 0 * ;
: RECURSE R> R> 2 - >R >R EXIT ;
: ( LIT@ ) WORD SCMP NOT SKIP? RECURSE ; 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
RECURSE: RS TOS is for RECURSE itself, then we have to dig
one more level to get to RECURSE's parent's caller.
IF true, skip following (fbr). Also, push br cell ref H,
to PS )
: IF ['] SKIP? , ['] (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
: ? @ . ;
: VARIABLE CREATE 2 ALLOT ;
: CONSTANT CREATE H ! DOES> @ ;
: = CMP NOT ;
: < CMP 0 1 - = ;
: > CMP 1 = ;