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097c7f4590
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Extends the iter-92 brainfuck.ml subset interpreter with bracket
matching:
'[' if mem[ptr] = 0, jump past matching ']'
(forward depth-counting scan: '[' increments depth, ']' decrements)
']' if mem[ptr] <> 0, jump back to matching '['
(backward depth-counting scan)
Test program '+++[.-]':
+++ set cell 0 = 3
[ enter loop (cell != 0)
. acc += cell
- cell -= 1
] loop while cell != 0
result: acc = 3 + 2 + 1 = 6
Tests deeply nested while loops, mutable pc / ptr / acc, multi-arm
if/else if dispatch on chars + nested begin/end blocks for loop
body conditionals.
58 baseline programs total.
43 lines
1.1 KiB
OCaml
43 lines
1.1 KiB
OCaml
let interpret prog =
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let mem = Array.make 256 0 in
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let ptr = ref 0 in
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let pc = ref 0 in
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let n = String.length prog in
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let acc = ref 0 in
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while !pc < n do
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let c = prog.[!pc] in
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(if c = '>' then ptr := !ptr + 1
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else if c = '<' then ptr := !ptr - 1
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else if c = '+' then mem.(!ptr) <- mem.(!ptr) + 1
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else if c = '-' then mem.(!ptr) <- mem.(!ptr) - 1
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else if c = '.' then acc := !acc + mem.(!ptr)
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else if c = '[' then begin
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if mem.(!ptr) = 0 then begin
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let depth = ref 1 in
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while !depth > 0 do
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pc := !pc + 1;
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let c = prog.[!pc] in
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if c = '[' then depth := !depth + 1
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else if c = ']' then depth := !depth - 1
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done
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end
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end
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else if c = ']' then begin
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if mem.(!ptr) <> 0 then begin
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let depth = ref 1 in
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while !depth > 0 do
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pc := !pc - 1;
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let c = prog.[!pc] in
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if c = ']' then depth := !depth + 1
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else if c = '[' then depth := !depth - 1
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done
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end
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end);
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pc := !pc + 1
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done;
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!acc
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;;
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interpret "+++[.-]"
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