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Brainfuck Interpreter
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# -*- coding: utf-8 -*- | |
import os | |
import sys | |
import time | |
IP = 0 # Instruction pointer | |
DP = 0 # Data pointer | |
DATA = [0] * 20 | |
OUTPUT = [] | |
def search_matching_bracket(text, direction): | |
brackets = ("[", "]") | |
if direction == "backwards": | |
brackets = brackets[::-1] # use ("]", "[") instead | |
text = text[::-1] # revert text | |
same_bracket, matching_bracket = brackets | |
matching_found = 0 | |
for index, char in enumerate(text): | |
if char == same_bracket: | |
matching_found -= 1 | |
elif char == matching_bracket: | |
matching_found += 1 | |
if matching_found == 1: | |
return index | |
raise Exception("Unbalanced brackets in program") | |
def jump_to_matching_bracket(program, current_position, direction): | |
if direction == 1: # search forward | |
index = search_matching_bracket(program[current_position:], | |
"forwards") | |
return current_position + index | |
else: | |
index = search_matching_bracket(program[:current_position], | |
"backwards") | |
return current_position - (index + 1) | |
def show_state(program): | |
os.system("clear") | |
state = ( | |
"OUT: {output}\n" | |
"{program}\n{instruction_pointer}\n" | |
"{data}\n{data_pointer}^" | |
).format( | |
output="".join(OUTPUT), | |
program=program, | |
instruction_pointer=(" " * IP) + "^", | |
data="|" + "|".join(map(lambda x: str(x).rjust(3), DATA)) + "|", | |
data_pointer=(" " * DP) + " " | |
) | |
print state | |
if __name__ == "__main__": | |
# This BF program prints "Hello World!" | |
program = ("++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++" | |
"++..+++.>>.<-.<.+++.------.--------.>>+.>++.") | |
DEBUG = '--debug' in sys.argv | |
while 1: | |
try: | |
next_instruction = program[IP] | |
except IndexError: | |
# we've reached the end of the program | |
show_state(program) | |
break | |
if DEBUG: | |
show_state(program) | |
time.sleep(0.01) | |
if next_instruction == ">": | |
DP += 1 | |
elif next_instruction == "<": | |
DP -= 1 | |
elif next_instruction == "+": | |
DATA[DP] += 1 | |
if DATA[DP] > 255: # rollover to 0 when overflowing | |
DATA[DP] = 0 | |
elif next_instruction == "-": | |
DATA[DP] -= 1 | |
if DATA[DP] < 0: # rollover to 255 when underflowing | |
DATA[DP] = 255 | |
elif next_instruction == ".": | |
OUTPUT.append(chr(DATA[DP])) | |
elif next_instruction == ",": | |
done = False | |
while not done: | |
try: | |
val = input("Enter a value (0-255):") | |
if 0 <= val <= 255: | |
done = True | |
DATA[DP] = val | |
except NameError: | |
pass | |
elif next_instruction == "[": | |
if DATA[DP] == 0: | |
IP = jump_to_matching_bracket(program, IP, 1) | |
elif next_instruction == "]": | |
if DATA[DP] != 0: | |
IP = jump_to_matching_bracket(program, IP, -1) | |
IP += 1 |
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