brainfuck.py

'''https://en.wikipedia.org/wiki/Brainfuck#Commands'''

import sys, mit
mit.State().globalize(globals())

def ass_inc(): ass(LIT_1); ass(ADD)
def ass_dec(): ass(LIT_1); ass(NEGATE); ass(ADD)
def ass_dup(): ass(LIT_0); ass(DUP);
def ass_over(): ass(LIT_1); ass(DUP);
def ass_loadb(): ass(LIT_0); ass(LOAD);
def ass_storeb(): ass(LIT_0); ass(STORE);

lit(0) # Data pointer.
stack = [] # [(start of loop, word to patch)]
for c in sys.stdin.read():
    if c == '>': ass_inc()
    elif c == '<': ass_dec()
    elif c == '+': ass_dup(); ass_loadb(); ass_inc(); ass_over(); ass_storeb()
    elif c == '-': ass_dup(); ass_loadb(); ass_dec(); ass_over(); ass_storeb()
    elif c == '.':
        ass_dup() # buffer
        ass(LIT_1) # length
        lit(LIB_C_STDOUT); ass_extra(LIB_C, type=BRANCH)
        lit(LIB_C_WRITE); ass_extra(LIB_C, type=BRANCH)
        ass(LIT_1); ass(POP);
    elif c == ',':
        ass_dup() # buffer
        ass(LIT_1) # length
        lit(LIB_C_STDIN); ass_extra(LIB_C, type=BRANCH)
        lit(LIB_C_READ); ass_extra(LIB_C, type=BRANCH)
        ass(LIT_1); ass(POP);
    elif c == '[':
        loop = label()
        ass_dup()
        ass_loadb()
        lit(0xDEADBEEF)
        patch = assembler.pc - mit.word_bytes
        ass(BRANCHZ)
        stack.append((loop, patch))
    elif c == ']':
        loop, patch = stack.pop()
        lit(loop)
        ass(BRANCH)
        M_word[patch] = label()
ass_extra(EXTRA_HALT)
M_word[mit.word_bytes] = label() # Patch data pointer.

save(sys.argv[1])