"""
A compatibility function 'iter' behaving like the built-in iter() function,
but returning objects which also providing the interface of lists.  It
considers that all the elements that remain to be produced form a list, and
this 'look-ahead' list can be indexed, sliced, and even mutated.

Note that operations like slicing or concatenating return 'collect' objects,
which behave more like lists in that iterating over them doesn't consume them.
If you really want the consuming behavior, you have to call iter() again.
"""

from collect import collect


class itercollect(collect):

    def __iter__(self):
        return self

    def next(self):
        try:
            result = self[0]
        except IndexError:
            raise StopIteration
        del self[0]
        return result


builtin_iter = iter

def iter(collection, *moreargs):
    if moreargs:
        collection = builtin_iter(collection, *moreargs)
    if not isinstance(collection, itercollect):
        collection = itercollect(collection)
    return collection


if __name__ == '__main__':
    import sys

    def ansi_print(text, esc, file=None):
        if file is None: file = sys.stderr
        text = text.rstrip()
        if sys.platform != "win32" and file.isatty():
            text = ('\x1b[%sm' % esc  +  
                    text +
                    '\x1b[0m')     # ANSI color code "reset"
        file.write(text + '\n')

    n = 10
    def f():
        global n
        n -= 1
        ansi_print(str(n), '31')
        return n

    it = iter(f, 0)