brainfuck

brainfuck-at-codewars.js

// Brainfuck.
// 
// codewars: https://www.codewars.com/kata/my-smallest-code-interpreter-aka-brainf-star-star-k/train/javascript
// brainfuck debug tool: http://www.iamcal.com/misc/bf_debug/
// brainfuck on wikipedia: https://zh.wikipedia.org/wiki/Brainfuck
function brainLuck(code, input){
  let codeInArray = code.split('');
  let inputInArray = input.split('');

  console.log(code);
  console.log(inputInArray);

  let ptc = 0;
  let ptr = 0;
  
  let output = '';
  let tape = [];
  let stack = [];
  let direction = 1;
  let isMoving = false;
  
  const instructions = {
    '>': () => !isMoving && (ptr ++),
    '<': () => !isMoving && (ptr --),
    // '+': () => !isMoving && (tape[ptr] = String.fromCharCode(((tape[ptr]||'\0').charCodeAt() + 1)%256)),
    '+': () => {
      if(isMoving) return;
      if(!tape[ptr]) {
        tape[ptr] = '\0';
      }
      tape[ptr] = String.fromCharCode((tape[ptr].charCodeAt() + 1) % 256);
    },
    '-': () => !isMoving && (tape[ptr] = String.fromCharCode(((tape[ptr]||'\0').charCodeAt() - 1)%256)),
    '.': () => !isMoving && (output += tape[ptr]),
    ',': () => !isMoving && (tape[ptr] = inputInArray.shift() || '\0'),
    '[': () => {
      stack.push(ptc);
      if (!isMoving && tape[ptr].charCodeAt() === 0) {
        isMoving = true;
      }
    },
    ']': () => {
      let last = stack.pop() - 1;
      if (tape[ptr].charCodeAt() !== 0) {
        ptc = last;
        console.log('go back ptc:', ptc);
        isMoving = false;
      }
    }
  }
  
  while (ptc < codeInArray.length) {
    let cmdName = codeInArray[ptc];
    console.log('cmd: ', cmdName, tape, ptr, isMoving);
    instructions[cmdName]();
    ptc += 1;
    
    console.log('output:', output);
  }
  
  return output;
}