Brainfuck

If you like programming and have looked around at various programming languages, then you've probably stumbled upon brainfuck at some point. For those unfamiliar with it, it is a non-practical, minimalistic language designed to amuse programmers.

Here's a "Hello World" program (source):


++++++++++[>+++++++>++++++++++>+++>+<<<<-]>++.>+.+++++++..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.>.


Yeah, check that shit out.  I can see you pissing your pants as I type this.  Here's a quick run down of what each character represents in brainfuck:

• + means increment the current cell.
• - means decrement the current cell.
• > means shift the current cell to the right.
• < means shift the current cell to the left.
• [ means begin a loop.
• ] means end of a loop, if the current cell  is not 0, jump to the beginning of the loop, else, continue (the [ and ] instructions can have a different meaning depending on the implementation, but they should behave the same way.
• . means print out the ASCII representation of the current cell.
• , means get an input and write it to the current cell.

As you can probably guess, writing in brainfuck is a bit of a ... brain fuck.  Programs are difficult to read for beginners, but with practice, it can be pretty easy to decipher brainfuck.  

Anyway, I decided to write my own brainfuck interpreter in python.  For any of you insane fucks interested, here is the source:

import sys

j=0
a = [0]
ptr = 0
loopbegin = 0
i = ""
x=0
while i !="`":
    try:
        x=0
        v = raw_input("\n~")
        while x < len(v):
            i = v[x]
            if i=='>':
                ptr+=1
                if  len(a) <= ptr:
                    a.append(0)
            elif i=='<':
                ptr-=1
            elif i=='+':
                a[ptr]+=1
            elif i=='-':
                a[ptr]-=1
            elif i==',':
                a[ptr] = ord(raw_input("~! "))
            elif i=='.':
                sys.stdout.write(chr(a[ptr]))
            elif i=='[':
                loopbegin = x
            elif i==']':
                if a[ptr] != 0:
                    x = loopbegin
            x+=1
    except:
        print("At char: %s: %s" %(i, ptr))
        print "Unexpected error:", sys.exc_info()[0]
        raise

I'm sure this can be optimized, and I think there is a bug with nested loops that I'm going ti work out tonight, but I don't really care that much since the language is not very useful anyway.  As for the specifics of my implementation:

• This version uses a dynamic array of cells, which -- since I'm using python -- has a maximum size of 536,870,912 elements on a 32 bit system.
• Since the array of cells is dynamic, its starting size is 1.  If the > operator is used, and the array is not large enough, it appends a new element to the end of the array.
• The ` character is used to quit the application.

Anyway, if you don't have python, you can always use the javascript implementation of brainfuck here.