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03e529b762
This scheme of "when we handle line-by-line, compile one word at a time then execute" so that we could allow words like "CREATE" to call "readword" before continuing was a bad scheme. It made things like branching outside of a colon definition impossible. This commit implement a new "litWord". When an undefined word is encountered at compile time, it is included as-is in a string literal word. It is at run time that we decide what to do with it.
43 lines
1.1 KiB
NASM
43 lines
1.1 KiB
NASM
; The Parameter stack (PS) is maintained by SP and the Return stack (RS) is
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; maintained by IX. This allows us to generally use push and pop freely because
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; PS is the most frequently used. However, this causes a problem with routine
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; calls: because in Forth, the stack isn't balanced within each call, our return
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; offset, when placed by a CALL, messes everything up. This is one of the
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; reasons why we need stack management routines below. IX always points to RS'
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; Top Of Stack (TOS)
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;
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; This return stack contain "Interpreter pointers", that is a pointer to the
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; address of a word, as seen in a compiled list of words.
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; Push value HL to RS
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pushRS:
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inc ix
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inc ix
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ld (ix), l
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ld (ix+1), h
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ret
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; Pop RS' TOS to HL
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popRS:
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ld l, (ix)
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ld h, (ix+1)
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dec ix
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dec ix
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ret
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; Verifies that SP is within bounds. If it's not, call ABORT
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chkPS:
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ld hl, (INITIAL_SP)
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; We have the return address for this very call on the stack. Let's
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; compensate
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dec hl \ dec hl
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or a ; clear carry
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sbc hl, sp
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ret nc ; (INITIAL_SP) >= SP? good
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; underflow
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ld hl, .msg
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call printstr
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jp abort
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.msg:
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.db "stack underflow", 0
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