basic: add variables
Things are getting cereal...
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@ -14,10 +14,12 @@
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.inc "lib/ari.asm"
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.inc "lib/parse.asm"
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.inc "lib/fmt.asm"
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.equ EXPR_PARSE parseLiteral
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.equ EXPR_PARSE parseLiteralOrVar
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.inc "lib/expr.asm"
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.inc "basic/tok.asm"
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.equ BUF_RAMSTART USER_RAMSTART
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.equ VAR_RAMSTART USER_RAMSTART
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.inc "basic/var.asm"
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.equ BUF_RAMSTART VAR_RAMEND
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.inc "basic/buf.asm"
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.equ BAS_RAMSTART BUF_RAMEND
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.inc "basic/main.asm"
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@ -12,6 +12,7 @@
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; *** Code ***
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basStart:
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ld (BAS_INITSP), sp
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call varInit
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call bufInit
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xor a
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ld hl, .welcome
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@ -51,8 +52,20 @@ basLoop:
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; If found, jump to it. If not found, unset Z. We expect commands to set Z
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; on success. Therefore, when calling basCallCmd results in NZ, we're not sure
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; where the error come from, but well...
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; Before being evaluated, (HL) is copied in BAS_SCRATCHPAD because some
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; evaluation routines (such as parseExpr) mutate the string it evaluates.
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; TODO: straighten this situation up. Mutating a string like this breaks
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; expectations.
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basCallCmd:
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; First, get cmd length
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push de ; --> lvl 1
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ld de, BAS_SCRATCHPAD
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call strcpy
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ex de, hl ; HL now points to scratchpad
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pop de ; <-- lvl 1
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; let's see if it's a variable assignment.
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call varTryAssign
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ret z ; Done!
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; Second, get cmd length
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call fnWSIdx
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cp 7
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jp nc, unsetZ ; Too long, can't possibly fit anything.
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97
apps/basic/var.asm
Normal file
97
apps/basic/var.asm
Normal file
@ -0,0 +1,97 @@
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; *** Variables ***
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; A list of words for each member of the A-Z range.
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.equ VAR_TBL VAR_RAMSTART
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.equ VAR_RAMEND @+52
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; *** Code ***
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varInit:
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ld b, VAR_RAMEND-VAR_RAMSTART
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ld hl, VAR_RAMSTART
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xor a
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.loop:
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ld (hl), a
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inc hl
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djnz .loop
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ret
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; Check if A is a valid variable letter (a-z or A-Z). If it is, set A to a
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; valid VAR_TBL index and set Z. Otherwise, unset Z (and A is destroyed)
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varChk:
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call upcase
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sub 'A'
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ret c ; Z unset
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cp 27 ; 'Z' + 1
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jr c, .isVar
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; A > 'Z'
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dec a ; unset Z
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ret
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.isVar:
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cp a ; set Z
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ret
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; Try to interpret line at (HL) and see if it's a variable assignment. If it
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; is, proceed with the assignment and set Z. Otherwise, NZ.
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varTryAssign:
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inc hl
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ld a, (hl)
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dec hl
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cp '='
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ret nz
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ld a, (hl)
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call varChk
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ret nz
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; We have a variable! Its table index is currently in A.
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push ix ; --> lvl 1
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push hl ; --> lvl 2
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push af ; --> lvl 3. save for later
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; Let's start by evaluating that expression
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inc hl \ inc hl
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call parseExpr ; --> number in IX
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jr nz, .exprErr
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pop af ; <-- lvl 3
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add a, a ; * 2 because each element is a word
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ld hl, VAR_TBL
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call addHL
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; HL placed, write number
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push de ; --> lvl 3
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push ix \ pop de
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ld (hl), e
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inc hl
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ld (hl), d
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pop de ; <-- lvl 3
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xor a ; ensure Z
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.end:
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pop hl ; <-- lvl 2
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pop ix ; <-- lvl 1
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ret
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.exprErr:
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pop af ; <-- lvl 3
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jr .end
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; Check if value at (HL) is a variable. If yes, returns its associated value.
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; Otherwise, jump to parseLiteral.
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parseLiteralOrVar:
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inc hl
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ld a, (hl)
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dec hl
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or a
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; if more than one in length, it can't be a variable
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jp nz, parseLiteral
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ld a, (hl)
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call varChk
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jp nz, parseLiteral
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; It's a variable, resolve!
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add a, a ; * 2 because each element is a word
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push hl ; --> lvl 1
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ld hl, VAR_TBL
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call addHL
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push de ; --> lvl 2
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ld e, (hl)
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inc hl
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ld d, (hl)
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push de \ pop ix
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pop de ; <-- lvl 2
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pop hl ; <-- lvl 1
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cp a ; ensure Z
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ret
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