mirror of
https://github.com/hsoft/collapseos.git
synced 2024-12-05 13:08:05 +11:00
105 lines
2.0 KiB
NASM
105 lines
2.0 KiB
NASM
; *** Variables ***
|
|
; A list of words for each member of the A-Z range.
|
|
.equ VAR_TBL VAR_RAMSTART
|
|
.equ VAR_RAMEND @+52
|
|
|
|
; *** Code ***
|
|
|
|
varInit:
|
|
ld b, VAR_RAMEND-VAR_RAMSTART
|
|
ld hl, VAR_RAMSTART
|
|
xor a
|
|
.loop:
|
|
ld (hl), a
|
|
inc hl
|
|
djnz .loop
|
|
ret
|
|
|
|
; Check if A is a valid variable letter (a-z or A-Z). If it is, set A to a
|
|
; valid VAR_TBL index and set Z. Otherwise, unset Z (and A is destroyed)
|
|
varChk:
|
|
call upcase
|
|
sub 'A'
|
|
ret c ; Z unset
|
|
cp 27 ; 'Z' + 1
|
|
jr c, .isVar
|
|
; A > 'Z'
|
|
dec a ; unset Z
|
|
ret
|
|
.isVar:
|
|
cp a ; set Z
|
|
ret
|
|
|
|
; Try to interpret line at (HL) and see if it's a variable assignment. If it
|
|
; is, proceed with the assignment and set Z. Otherwise, NZ.
|
|
varTryAssign:
|
|
inc hl
|
|
ld a, (hl)
|
|
dec hl
|
|
cp '='
|
|
ret nz
|
|
ld a, (hl)
|
|
call varChk
|
|
ret nz
|
|
; We have a variable! Its table index is currently in A.
|
|
push ix ; --> lvl 1
|
|
push hl ; --> lvl 2
|
|
push de ; --> lvl 3
|
|
push af ; --> lvl 4. save for later
|
|
; Let's put that expression to read in scratchpad
|
|
inc hl \ inc hl
|
|
ld de, SCRATCHPAD
|
|
call rdWord
|
|
ex de, hl
|
|
; Now, evaluate that expression now in (HL)
|
|
call parseExpr ; --> number in DE
|
|
jr nz, .exprErr
|
|
pop af ; <-- lvl 4
|
|
call varAssign
|
|
xor a ; ensure Z
|
|
.end:
|
|
pop de ; <-- lvl 3
|
|
pop hl ; <-- lvl 2
|
|
pop ix ; <-- lvl 1
|
|
ret
|
|
.exprErr:
|
|
pop af ; <-- lvl 4
|
|
jr .end
|
|
|
|
; Given a variable **index** in A (call varChk to transform) and a value in
|
|
; DE, assign that value in the proper cell in VAR_TBL.
|
|
; No checks are made.
|
|
varAssign:
|
|
push hl
|
|
add a, a ; * 2 because each element is a word
|
|
ld hl, VAR_TBL
|
|
call addHL
|
|
; HL placed, write number
|
|
ld (hl), e
|
|
inc hl
|
|
ld (hl), d
|
|
pop hl
|
|
ret
|
|
|
|
; Check if value at (HL) is a variable. If yes, returns its associated value.
|
|
; Otherwise, jump to parseLiteral.
|
|
parseLiteralOrVar:
|
|
call isLiteralPrefix
|
|
jp z, parseLiteral
|
|
; not a literal, try var
|
|
ld a, (hl)
|
|
call varChk
|
|
ret nz
|
|
; It's a variable, resolve!
|
|
add a, a ; * 2 because each element is a word
|
|
push hl ; --> lvl 1
|
|
ld hl, VAR_TBL
|
|
call addHL
|
|
ld e, (hl)
|
|
inc hl
|
|
ld d, (hl)
|
|
pop hl ; <-- lvl 1
|
|
inc hl ; point to char after variable
|
|
cp a ; ensure Z
|
|
ret
|