Initial commit

Author: Alex

bf.py

@@ -0,0 +1,109 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+"""
+Python Brainfuck interpreter.
+"""
+
+from __future__ import with_statement
+from sys import argv, stdin, stdout
+
+# Cells and pointer
+IND   = 0
+CELLS = []
+
+
+def every_char_from(flow):
+    """Yields every char from flow.
+    """
+    for row in flow:
+        for char in row:
+            yield char
+
+
+def get_char():
+    """Quick and dirty getchar implementation.
+    """
+    try:
+        return raw_input()[0]
+    except EOFError:
+        return '0'
+
+
+def init():
+    """We have lazy cell creation with this.
+    """
+    global CELLS, IND
+
+    if len(CELLS) - 1 < IND:
+        CELLS.append(0)
+
+
+def nested(chars):
+    """Looking for the next same-level ']'.
+    """
+    i = 0
+
+    while chars[0:i+1].count("[") != chars[0:i+1].count("]"):
+        i += 1
+
+    return chars[1:i]
+
+
+
+def run(chars):
+    """Run a sequence of chars.
+    """
+    global CELLS, IND
+
+    init()
+    position = 0
+
+    while position < len(chars):
+        char = chars[position]
+
+        if char == '>':
+            IND += 1
+            init() # if it is a not-yet-visited cell, we put a 0
+
+        elif char == '<':
+            if IND: # IND is always >= 0
+                IND -= 1
+
+        elif char == '+':
+            CELLS[IND] += 1
+
+        elif char == '-':
+            if CELLS[IND]: # values are >= 0
+                CELLS[IND] -= 1
+
+        elif char == '.':
+            stdout.write(chr(CELLS[IND] % 256))
+
+        elif char == ',':
+            CELLS[IND] = ord(get_char())
+
+        elif char == '[':
+            nest = nested(chars[position:])
+
+            while CELLS[IND]:
+                run(nest)
+
+            position += len(nest) + 1
+
+        position += 1
+
+
+if __name__ == '__main__':
+
+    if not stdin.isatty():
+        run(list(every_char_from(stdin)))
+
+    elif len(argv) > 1:
+        with open(argv[1]) as f:
+            run(list(every_char_from(f)))
+
+    else:
+        print 'Usage: %s file' % argv[0]
+        print 'Usage: cat file | %s' % argv[0]
+

hello.bf

@@ -0,0 +1,21 @@
++++++ +++++             initialize counter (cell #0) to 10
+[                       use loop to set the next four cells to 70/100/30/10
+> +++++ ++              add  7 to cell #1
+> +++++ +++++           add 10 to cell #2
+> +++                   add  3 to cell #3
+> +                     add  1 to cell #4
+<<<< -                  decrement counter (cell #0)
+]
+> ++ .                  print 'H'
+> + .                   print 'e'
++++++ ++ .              print 'l'
+.                       print 'l'
++++ .                   print 'o'
+> ++ .                  print ' '
+<< +++++ +++++ +++++ .  print 'W'
+> .                     print 'o'
++++ .                   print 'r'
+----- - .               print 'l'
+----- --- .             print 'd'
+> + .                   print '!'
+> .                     print '\n'