Interpreter for language "brainfuck".

brainfuck lang.py

# Python 2.7 interpreter of esoteric programming language named "Brainfu**". You can reed more here:
# https://en.wikipedia.org/wiki/Brainfuck
# To run this interpreter, just type something like this:
#
# Interpreter.run('++++++++++[.-]')
#
# (This program will print numbers from 10 to 1)

MEMORY_SIZE = 30000
SIZE_OF_CELL = 256


class Interpreter(object):
    @staticmethod
    def run(code):
        selected_cell = 0

        # Stack trace for loops
        stack_trace = []

        memory = [0 for _ in xrange(MEMORY_SIZE)]

        i = 0
        while i < len(code):
            char = code[i]

            if char == '>':
                if selected_cell == MEMORY_SIZE - 1:
                    selected_cell = 0
                selected_cell += 1

            elif char == '<':
                if selected_cell == 0:
                    selected_cell = MEMORY_SIZE - 1
                selected_cell -= 1

            elif char == '+':
                if memory[selected_cell] == SIZE_OF_CELL - 1:
                    memory[selected_cell] = 0
                memory[selected_cell] += 1

            elif char == '-':
                if memory[selected_cell] == 0:
                    memory[selected_cell] = SIZE_OF_CELL - 1
                memory[selected_cell] -= 1

            elif char == '.':
                print memory[selected_cell]

            elif char == ',':
                memory[selected_cell] = int(raw_input())

            elif char == '[':
                opened = 0
                closed = 0
                start = 0
                prev_opened = 0
                end = len(code)

                for j in range(i, len(code)):
                    if code[j] == '[':
                        opened += 1
                    if code[j] == ']':
                        closed += 1
                    if opened != 0 and prev_opened == 0:
                        start = j
                    if opened != 0 and closed != 0 and opened == closed:
                        end = j
                        break

                    prev_opened = opened

                stack_trace.append({'start': start, 'end': end})

                if memory[selected_cell] == 0:
                    i = end

            elif char == ']':
                if not memory[selected_cell] == 0:
                    for item in stack_trace:
                        if item['end'] == i and memory[selected_cell] != 0:
                            i = item['start']
                            break

            i += 1