diff options
| -rw-r--r-- | eval.s | 589 |
1 files changed, 327 insertions, 262 deletions
@@ -4,292 +4,357 @@ a (the environment / symbol table) at a known location ; e to be evaluated in R0 ; result of evaluation in R0 eval: (e) = - BIT #1, (R0) ; test if e is cons or atom - BEQ not_atom ; branch if not atom(e) - JSR PC, #assoc ; return assoc(e) - RTS PC +003000 032710 BIT #1, (R0) ; test if e is cons or atom +003002 000001 +003004 001403 BEQ not_atom ; branch if not atom(e) +003006 004737 JSR PC, #assoc ; return assoc(e) +003010 004500 +003012 000207 RTS PC not_atom: - ; R7 = PC - ; R6 = SP - ; R5 = a (symbol table) - ; R4 = e (original sexp) - ; R3 = args = tl = cdr(e) - ; R2 = hd, symbols = second = car(cdr(hd)) - ; R1 = arg2 - ; R0 = arg1, result - MOV R0, R4 ; save e - MOV @R4, R2 ; hd <- car(e) - BIT #1, (R2) ; test if hd is cons or atom - BNE head_is_atom ; branch if atom(hd) - ;otherwise (if cons): - MOV @R2, R0 ; arg1 <- car(hd) = first - MOV "LABEL", R1 ; arg2 <- at"LABEL" - JSR PC, #eq ; test eq(first, at"LABEL") - BNE not_label ; branch if not label - ; if is label - MOV 2(R2), R2 ; rest <- cdr(hd) - MOV 2(R2), R3 ; rest' <- cdr(rest) - ; R2 = rest - ; R3 = rest' - ; push entry l[second, hd] onto symbol table a - ; a <- cons(l[second, hd], a) - MOV @R2, (R5)+ ; push second (=car(rest)) onto symbol table column 0 - MOV @R4, (R5)+ ; push hd onto symbol table column 1 - ; evaluate cons(third, tl) in extended environment - ; R0 <- cons(third, tl) - MOV @R3, R0 ; arg1 <- third (=car(rest')) - MOV 2(R4), R1 ; arg2 <- tl = cdr(e) - JSR PC, #cons ; result in R0 - JSR PC, #eval ; result <- eval(cons(third, tl)) - SUB 4, R5 ; pop off symbol table entry - RTS PC ; return result in R0 +; R7 = PC +; R6 = SP +; R5 = a (symbol table) +; R4 = e (original sexp) +; R3 = args = tl = cdr(e) +; R2 = hd, symbols = second = car(cdr(hd)) +; R1 = arg2 +; R0 = arg1, result +003014 010004 MOV R0, R4 ; save e +003016 011402 MOV @R4, R2 ; hd <- car(e) +003020 032712 BIT #1, (R2) ; test if hd is cons or atom +003022 000001 +003024 000137 JMP head_is_atom ; branch if atom(hd) +003026 003300 +; otherwise (if cons): +003030 011200 MOV @R2, R0 ; arg1 <- car(hd) = first +003032 012701 MOV "LABEL", R1 ; arg2 <- at"LABEL" +003034 005076 +003036 004737 JSR PC, #eq ; test eq(first, at"LABEL") +003040 003700 +000042 001020 BNE not_label ; branch if not label +; if is label +003044 016202 MOV 2(R2), R2 ; rest <- cdr(hd) +003046 000002 +003050 016203 MOV 2(R2), R3 ; rest' <- cdr(rest) +003052 000002 +; R2 = rest +; R3 = rest' +; push entry l[second, hd] onto symbol table a +; a <- cons(l[second, hd], a) +003054 011225 MOV @R2, (R5)+ ; push second (=car(rest)) onto symbol table column 0 +003056 011425 MOV @R4, (R5)+ ; push hd onto symbol table column 1 +; evaluate cons(third, tl) in extended environment +; R0 <- cons(third, tl) +003060 011300 MOV @R3, R0 ; arg1 <- third (=car(rest')) +003062 016401 MOV 2(R4), R1 ; arg2 <- tl = cdr(e) +003064 000002 +003066 004737 JSR PC, #cons ; result in R0 +003070 004400 +003072 004737 JSR PC, #eval ; result <- eval(cons(third, tl)) +003074 003000 +003076 162705 SUB 4, R5 ; pop off symbol table entry +003100 000004 +003102 000207 RTS PC ; return result in R0 not_label: - ; R2 = hd - MOV @R2, R0 ; arg1 <- car(hd) = first - MOV "LAMBDA", R1 ; arg2 <- at"LAMBDA" - JSR PC, #eq ; test eq(first, at"LAMBDA") - BNE error ; branch if not lambda - ; if is lambda - ; push onto a ; a <- append(pair(second, evlis(tl)), a) - MOV R5, -(SP) ; push old symbol table pointer to stack - MOV 2(R2), R1 ; rest <- cdr(hd) - MOV @R1, R2 ; symbols <- car(rest) = second - MOV 2(R4), R3 ; args <- tl = cdr(e) - MOV R1, -(SP) ; save rest - ; R2 = symbols - ; R3 = args - evlis: (symbols, args) - BIT #1, (R2) ; test if symbols is cons or atom - BNE done ; if its atom jump to done - ; if its cons: - BIT #1, (R3) ; test if args is cons or atom - BNE done ; if its atom jump to done - ; if both are cons: - MOV @R3, R0 ; arg1 <- car(args) - MOV R2, -(SP) ; save symbos - MOV R3, -(SP) ; save args - JSR PC, #eval ; result <- eval (arg1) - MOV (SP)+, R3 ; restore args - MOV (SP)+, R2 ; restore symbols - ; push (symbol, eval(arg)) - MOV @R2, (R5)+ ; push symbol (=car(symbols)) to column 0 - MOV R0, (R5)+ ; push result to column 1 - MOV 2(R2), R2 ; args <- cdr(args) - MOV 2(R3), R3 ; symbols <- cdr(symbols) - BR -??? ; jump to evlis(symbols, args) - done: - MOV (SP)+, R1 ; restore rest - ; R1 = rest - MOV 2(R1), R1 ; rest' <- cdr(rest) - MOV @R1, R0 ; arg1 <- third = car(rest') - JSR PC, #eval ; result <- eval(third) - ; pop off argument entries - MOV (SP)+, R5 ; restore symbol table pointer - RTS PC +; R2 = hd +003104 011200 MOV @R2, R0 ; arg1 <- car(hd) = first +003106 012701 MOV "LAMBDA", R1 ; arg2 <- at"LAMBDA" +003110 005104 +003112 004737 JSR PC, #eq ; test eq(first, at"LAMBDA") +003114 003700 +003116 001043 BNE error ; branch if not lambda +; if is lambda +; push onto a ; a <- append(pair(second, evlis(tl)), a) +003120 010546 MOV R5, -(SP) ; push old symbol table pointer to stack +003122 016201 MOV 2(R2), R1 ; rest <- cdr(hd) +003124 000002 +003126 011102 MOV @R1, R2 ; symbols <- car(rest) = second +003130 016403 MOV 2(R4), R3 ; args <- tl = cdr(e) +003132 000002 +003134 010146 MOV R1, -(SP) ; save rest +; R2 = symbols +; R3 = args +evlis: (symbols, args) +003134 032712 BIT #1, (R2) ; test if symbols is cons or atom +003136 000001 +003140 001021 BNE done ; if its atom jump to done +; if its cons: +003142 032713 BIT #1, (R3) ; test if args is cons or atom +003144 000001 +003146 001016 BNE done ; if its atom jump to done +; if both are cons: +003150 011300 MOV @R3, R0 ; arg1 <- car(args) +003152 010246 MOV R2, -(SP) ; save symbos +003154 010346 MOV R3, -(SP) ; save args +003156 004737 JSR PC, #eval ; result <- eval (arg1) +003160 003000 +003162 012603 MOV (SP)+, R3 ; restore args +003164 012602 MOV (SP)+, R2 ; restore symbols +; push (symbol, eval(arg)) +003166 011225 MOV @R2, (R5)+ ; push symbol (=car(symbols)) to column 0 +003170 010025 MOV R0, (R5)+ ; push result to column 1 +003172 016202 MOV 2(R2), R2 ; args <- cdr(args) +003174 000002 +003176 016303 MOV 2(R3), R3 ; symbols <- cdr(symbols) +003200 000002 +003202 000754 BR -40 ; jump to evlis(symbols, args) +done: +003204 012601 MOV (SP)+, R1 ; restore rest +; R1 = rest +003206 016101 MOV 2(R1), R1 ; rest' <- cdr(rest) +003210 000002 +003212 011100 MOV @R1, R0 ; arg1 <- third = car(rest') +003214 004737 JSR PC, #eval ; result <- eval(third) +003216 003000 +; pop off argument entries +003220 012605 MOV (SP)+, R5 ; restore symbol table pointer +003222 000207 RTS PC error: - BR -2 ; infinite loop +003224 000777 BR -2 ; infinite loop head_is_atom: - ; R2 = hd - ; R3 = tl - ; R4 = e - MOV 2(R4), R3 ; tl <- cdr(e) - MOV R2, R0 ; arg1 <- hd - MOV "QUOTE", R1 ; arg2 <- at"QUOTE" - JSR PC, #eq ; test eq(hd, at"QUOTE") - BNE next ; skip if not quote - ; return car(tl) - MOV @R3, R0 - RTS PC +; R2 = hd +; R3 = tl +; R4 = e +003300 016403 MOV 2(R4), R3 ; tl <- cdr(e) +003302 000002 +003304 010200 MOV R2, R0 ; arg1 <- hd +003306 012701 MOV "QUOTE", R1 ; arg2 <- at"QUOTE" +003310 005016 +003312 004737 JSR PC, #eq ; test eq(hd, at"QUOTE") +003314 003700 +003316 001002 BNE next ; skip if not quote +; return car(tl) +003320 011300 MOV @R3, R0 +003322 000207 RTS PC - next: - MOV R2, R0 ; arg1 <- hd - MOV "ATOM", R1 ; arg2 <- at"ATOM" - JSR PC, #eq ; test eq(hd, at"ATOM") - BNE next ; skip if not atom - ; return atom(eval(car(tl))) - MOV @R3, R0 ; arg1 <- car(tl) - JSR PC, #eval ; result <- eval(car(tl)) - BIT #1, (R0) ; test if e is cons or atom - BEQ not_atom ; branch if not atom - ; is atom - MOV "T" R0 - BR return - ; not_atom - MOV "F" R0 - RTS PC +next: +003324 010200 MOV R2, R0 ; arg1 <- hd +003326 012701 MOV "ATOM", R1 ; arg2 <- at"ATOM" +003330 005026 +003332 004737 JSR PC, #eq ; test eq(hd, at"ATOM") +003334 003700 +003336 001014 BNE next ; skip if not atom +; return atom(eval(car(tl))) +003340 011300 MOV @R3, R0 ; arg1 <- car(tl) +003342 004737 JSR PC, #eval ; result <- eval(car(tl)) +003344 003000 +003346 032710 BIT #1, (R0) ; test if e is cons or atom +003350 000001 +003352 001403 BEQ not_atom ; branch if not atom +; is atom +003354 012700 MOV "T" R0 +003356 005006 +003160 000207 RTS PC +; not_atom +003362 012700 MOV "F" R0 +003364 005012 +003366 000207 RTS PC - next: - MOV R2, R0 ; arg1 <- hd - MOV "EQ", R1 ; arg2 <- at"EQ" - JSR PC, #eq ; test eq(hd, at"EQ") - BNE next ; skip if not eq - ; return eq(eval(car(tl)), eval(cadr(tl))) - MOV @R3, R0 ; arg1 <- car(tl) - MOV R3, -(SP) ; save tl - JSR PC, #eval ; result <- eval(car(tl)) - MOV (SP)+, R3 ; restore tl - MOV R0, -(SP) ; push eq arg1 = result - MOV 2(R3), R0 ; rest <- cdr(tl) - MOV @R0, R0 ; arg1 <- car(rest) - JSR PC, #eval ; result <- eval(cadr(tl)) - MOV R0, R1 ; arg2 <- result - MOV (SP)+, R0 ; pop arg1 - JSR PC, #eq ; test if equal - BNE not_eq - ; eq - MOV "T" R0 - BR return - ; not_eq - MOV "F" R0 - RTS PC +next: +003370 010200 MOV R2, R0 ; arg1 <- hd +003372 012701 MOV "EQ", R1 ; arg2 <- at"EQ" +003374 005036 +003376 004737 JSR PC, #eq ; test eq(hd, at"EQ") +003400 003700 +003402 001026 BNE next ; skip if not eq +; return eq(eval(car(tl)), eval(cadr(tl))) +003404 011300 MOV @R3, R0 ; arg1 <- car(tl) +003406 010346 MOV R3, -(SP) ; save tl +003410 004737 JSR PC, #eval ; result <- eval(car(tl)) +003412 003000 +003414 012603 MOV (SP)+, R3 ; restore tl +003416 010046 MOV R0, -(SP) ; push eq arg1 = result +003420 016300 MOV 2(R3), R0 ; rest <- cdr(tl) +003422 000002 +003424 011000 MOV @R0, R0 ; arg1 <- car(rest) +003426 004737 JSR PC, #eval ; result <- eval(cadr(tl)) +003430 003000 +003432 010001 MOV R0, R1 ; arg2 <- result +003134 012600 MOV (SP)+, R0 ; pop arg1 +003436 004737 JSR PC, #eq ; test if equal +003440 003700 +003442 001003 BNE not_eq +; eq +003444 012700 MOV "T" R0 +003446 005006 +003450 000207 RTS PC +; not_eq +003452 012700 MOV "F" R0 +003454 005012 +003456 000207 RTS PC - next: - MOV R2, R0 ; arg1 <- hd - MOV "COND", R1 ; arg2 <- at"COND" - JSR PC, #eq ; test eq(hd, at"COND") - BNE next ; skip if not cond - ; return evcon(car(tl)) - MOV @R3, R2 ; arg1 <- car(tl) - evcon: - ; R1 = arg1 = at"T" - ; R2 = c - MOV @R2, R0 ; car(c) - MOV @R0, R0 ; arg1 <- caar(c) - MOV R2, -(SP) ; save c - JSR PC, #eval ; arg1 <- eval(caar(c)) - MOV (SP)+, R2 ; restore c - MOV "T" R1 ; arg2 <- at"T" - JSR PC, #eq ; check if it's at"T" - BEQ is_true - ; if not true - MOV 2(R2), R2 ; c <- cdr(c) - BR -??? ; evcon(c) - ; if true - MOV @R2, R0 ; car(c) - MOV 2(R0), R0 ; cdar(c) - MOV @R0, R0 ; arg1 <- cadar(c) - JSR PC, #eval ; result <- eval(cadar(c)) - RTS PC +next: +003460 010200 MOV R2, R0 ; arg1 <- hd +003462 012701 MOV "COND", R1 ; arg2 <- at"COND" +003464 005044 +003466 004737 JSR PC, #eq ; test eq(hd, at"COND") +003470 003700 +003472 001025 BNE next ; skip if not cond +; return evcon(car(tl)) +003474 011302 MOV @R3, R2 ; arg1 <- car(tl) +evcon: +; R1 = arg1 = at"T" +; R2 = c +003476 011200 MOV @R2, R0 ; car(c) +003500 011000 MOV @R0, R0 ; arg1 <- caar(c) +003502 010246 MOV R2, -(SP) ; save c +003504 004737 JSR PC, #eval ; arg1 <- eval(caar(c)) +003506 003000 +003510 012602 MOV (SP)+, R2 ; restore c +003512 012701 MOV "T" R1 ; arg2 <- at"T" +003514 004737 JSR PC, #eq ; check if it's at"T" +003516 003700 +003520 001403 BEQ is_true +; if not true +003522 016202 MOV 2(R2), R2 ; c <- cdr(c) +003524 000002 +003526 000763 BR -26 ; evcon(c) +; if true +003530 011200 MOV @R2, R0 ; car(c) +003532 012700 MOV 2(R0), R0 ; cdar(c) +003534 000002 +003536 011000 MOV @R0, R0 ; arg1 <- cadar(c) +003540 004737 JSR PC, #eval ; result <- eval(cadar(c)) +003542 003000 +003544 000207 RTS PC - next: - MOV R2, R0 ; arg1 <- hd - MOV "CAR", R1 ; arg2 <- at"CAR" - JSR PC, #eq ; test eq(hd, at"CAR") - BNE next ; skip if not car - ; return car(eval(car(tl))) - MOV @R3, R0 ; arg1 <- car(tl) - JSR PC, #eval ; result <- eval(car(tl)) - MOV @R0, R0 ; result <- car(result) - RTS PC +next: +003546 010200 MOV R2, R0 ; arg1 <- hd +003550 012701 MOV "CAR", R1 ; arg2 <- at"CAR" +003552 005052 +003554 004737 JSR PC, #eq ; test eq(hd, at"CAR") +003556 003700 +003560 001005 BNE next ; skip if not car +; return car(eval(car(tl))) +003562 011300 MOV @R3, R0 ; arg1 <- car(tl) +003564 004737 JSR PC, #eval ; result <- eval(car(tl)) +003566 003000 +003570 011000 MOV @R0, R0 ; result <- car(result) +003572 000207 RTS PC - next: - MOV R2, R0 ; arg1 <- hd - MOV "CDR", R1 ; arg2 <- at"CDR" - JSR PC, #eq ; test eq(hd, at"CDR") - BNE next ; skip if not cdr - ; return cdr(eval(car(tl))) - MOV @R3, R0 ; arg1 <- car(tl) - JSR PC, #eval ; result <- eval(car(tl)) - MOV 2(R0), R0 ; result <- cdr(result) - RTS PC +next: +003574 010200 MOV R2, R0 ; arg1 <- hd +003576 012701 MOV "CDR", R1 ; arg2 <- at"CDR" +003600 005062 +003602 004737 JSR PC, #eq ; test eq(hd, at"CDR") +003604 003700 +003606 001006 BNE next ; skip if not cdr +; return cdr(eval(car(tl))) +003610 011300 MOV @R3, R0 ; arg1 <- car(tl) +003612 004737 JSR PC, #eval ; result <- eval(car(tl)) +003614 003000 +003616 016000 MOV 2(R0), R0 ; result <- cdr(result) +003620 000002 +003622 000207 RTS PC - next: - MOV R2, R0 ; arg1 <- hd - MOV "CONS", R1 ; arg2 <- at"CONS" - JSR PC, #eq ; test eq(hd, at"CONS") - BNE otherwise ; skip if not cons - ; return cons(eval(car(tl)), eval(cadr(tl))) - MOV @R3, R0 ; arg1 <- car(tl) - MOV R3, -(SP) ; save tl - JSR PC, #eval ; result <- eval(car(tl)) - MOV (SP)+, R3 ; restore tl - MOV R0, -(SP) ; push cons arg1 - MOV 2(R3), R0 ; rest <- cdr(tl) - MOV @R0, R0 ; arg1 <- car(rest) - JSR PC, #eval ; result <- eval(cadr(tl)) - MOV R0, R1 ; arg2 <- result - MOV (SP)+, R0 ; pop arg1 - JSR PC, #cons - RTS PC +next: +003624 010200 MOV R2, R0 ; arg1 <- hd +003626 012701 MOV "CONS", R1 ; arg2 <- at"CONS" +003630 004737 JSR PC, #eq ; test eq(hd, at"CONS") +003632 003700 +003634 001020 BNE otherwise ; skip if not cons +; return cons(eval(car(tl)), eval(cadr(tl))) +003636 011300 MOV @R3, R0 ; arg1 <- car(tl) +003640 010346 MOV R3, -(SP) ; save tl +003642 004737 JSR PC, #eval ; result <- eval(car(tl)) +003644 003000 +003646 012603 MOV (SP)+, R3 ; restore tl +003650 010046 MOV R0, -(SP) ; push cons arg1 +003652 016300 MOV 2(R3), R0 ; rest <- cdr(tl) +003654 000002 +003656 011000 MOV @R0, R0 ; arg1 <- car(rest) +003660 004737 JSR PC, #eval ; result <- eval(cadr(tl)) +003662 003000 +003664 010001 MOV R0, R1 ; arg2 <- result +003666 012600 MOV (SP)+, R0 ; pop arg1 +003670 004737 JSR PC, #cons +003672 004400 +003674 000207 RTS PC - otherwise: - return eval(cons(assoc(hd), tl))) - RTS PC +otherwise: +; return eval(cons(assoc(hd), tl))) +003676 000207 RTS PC ; This one touches R0, R1 eq: - ; R0 = arg1 - ; R1 = arg2 - - BIT #1, (R0) ; test if arg1 is cons or atom - BEQ bad ; if its cons jump to error - ; otherwise its atom - BIT #1, (R1) ; test if arg2 is cons or atom - BEQ bad ; if its cons jump to error - - ; get the string pointers out of atoms arg1 and arg2 - MOV @(R0), R0 - DEC R0 - MOV @(R1), R1 - DEC R1 +; R0 = arg1 +; R1 = arg2 +003700 032710 BIT #1, (R0) ; test if arg1 is cons or atom +003700 000001 +003700 001420 BEQ bad ; if its cons jump to error +; otherwise its atom +003700 032701 BIT #1, (R1) ; test if arg2 is cons or atom +003710 000001 +003712 001415 BEQ bad ; if its cons jump to error +; get the string pointers out of atoms arg1 and arg2 +003714 011000 MOV @(R0), R0 +003716 005300 DEC R0 +003720 011101 MOV @(R1), R1 +003722 005301 DEC R1 loop: - CMPB (R0), (R1)+ ; compare a byte from each string - ; advance R1 pointer - BNE not_equal - ; if they are equal: - TSTB (R0)+ ; check if null byte - ; advance R0 pointer - BEQ done ; if null byte, strings are equal - ; otherwise, not done yet: - BR loop +003724 121021 CMPB (R0), (R1)+ ; compare a byte from each string + ; advance R1 pointer +003726 001003 BNE not_equal +; if they are equal: +003730 105720 TSTB (R0)+ ; check if null byte + ; advance R0 pointer +003732 001403 BEQ done ; if null byte, strings are equal +; otherwise, not done yet: +003734 000773 BR loop not_equal: - ; the strings are not equal - CLZ ; clear zero flag - RTS PC +; the strings are not equal +003736 000244 CLZ ; clear zero flag +003740 000207 RTS PC done: - ; the strings are equal - SEZ ; set zero flag - RTS PC +; the strings are equal +003742 000264 SEZ ; set zero flag +003744 000207 RTS PC bad: - BR -2 ; infinite loop - +003746 000777 BR -2 ; infinite loop ; THIS ONE TOUCHES R0, R2 cons: - ; R0 = arg1 - ; R1 = arg2 - ; heap at 10000 - ; no garbage collection - ; pretend heap is infinite - MOV @#10000, R2 ; get free pointer - MOV R0, @R2 ; move arg1 to car of new cons cell - MOV R1, 2(R2) ; move arg2 to cdr of new cons cell - MOV R2, R0 ; result <- new cons cell - TST (R2)+ ; increment free pointer - MOV R2, @#10000 ; store new free pointer - RTS PC +; R0 = arg1 +; R1 = arg2 +; heap at 10000 +; no garbage collection +; pretend heap is infinite +004400 013702 MOV @#010000, R2 ; get free pointer +004402 010000 +004404 010012 MOV R0, @R2 ; move arg1 to car of new cons cell +004406 010162 MOV R1, 2(R2) ; move arg2 to cdr of new cons cell +004410 000002 +004412 010200 MOV R2, R0 ; result <- new cons cell +004414 062702 ADD 4, R2 ; advance free pointer +004416 000004 +004420 010237 MOV R2, @#010000 ; store new free pointer +004422 010000 +004424 000207 RTS PC ; This one touches R0, R1, R2, R4 assoc: - MOV R5, R4 - MOV R0, R2 - ; R1 = key - ; R2 = symbol - ; R4 = symbol table pointer - loop: - CMP R4, #10000 ; beginning of symbol table - BLOS bad ; symbol not found - ; otherwise check next row - TST -(R4) ; skip column 1 - MOV -(R4), R1 ; key <- column 0 - MOV R2, R0 ; arg1 <- symbol - JSR PC, #eq ; check if symbol equals key - BNE loop - ; otherwise they are equal - MOV 2(R4), R0 ; result <- value - RTS PC - bad: - BR -2 ; infinite loop +004500 010504 MOV R5, R4 +004502 010002 MOV R0, R2 +; R1 = key +; R2 = symbol +; R4 = symbol table pointer +loop: +004504 020437 CMP R4, #10000 ; beginning of symbol table +004506 010000 +004510 101411 BLOS bad ; symbol not found +; otherwise check next row +004512 005744 TST -(R4) ; skip column 1 +004514 014401 MOV -(R4), R1 ; key <- column 0 +004516 010200 MOV R2, R0 ; arg1 <- symbol +004520 004737 JSR PC, #eq ; check if symbol equals key +004522 003700 +004524 001367 BNE loop +; otherwise they are equal +004526 016400 MOV 2(R4), R0 ; result <- value +004530 000002 +004532 000207 RTS PC +bad: +004534 000777 BR -2 ; infinite loop |