Execute Brain****: Difference between revisions

Alternative version, simpler and faster.

<lang d>import core.stdc.stdio: getc, putchar, stdin, EOF;

import core.stdc.stdlib: exit;

void brainfuckRun(const string code) {

static pure int[int] matchBraces(const string code)

out(result) {

foreach (k, v; result) {

assert(k >=0 && k < code.length);

assert(v >=0 && v < code.length);

assert(v in result);

}

} body {

int[int] loops;

int[] loopStack;

foreach (i, instruction; code) {

if (instruction == '[')

loopStack ~= i;

else if (instruction == ']') {

assert(loopStack.length);

loops[i] = loopStack[$ - 1];

loopStack.length -= 1;

loops[loops[i]] = i;

}

}

assert(!loopStack.length);

return loops;

}

static void runCode(const string code, const int[int] loops) {

enum char empty = '\0';

char[30_000] tape = empty;

int cell, index;

while (index < cast(int)code.length) {

immutable int instruction = code[index];

switch (instruction) {

case '>': cell++; assert(cell < tape.length); break;

case '<': cell--; assert(cell >= 0); break;

case '+': tape[cell]++; break;

case '-': tape[cell]--; break;

case '.': putchar(tape[cell]); break;

case ',':

int c = getc(stdin);

if (c == EOF)

exit(1);

tape[cell] = cast(char)c;

break;

case '[':

if (tape[cell] == empty)

index = loops[index];

break;

case ']':

if (tape[cell] != empty)

index = loops[index];

break;

default: break;

}

index++;

}

}

int[int] loops = matchBraces(code);

runCode(code, loops);

}

void main() {

brainfuckRun("++++++++++[>+++++++>++++++++++>+++>+<<<<-]

>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.");

}</lang>