Stream.py

@datacon(Stream)
def filter(xs):
    @fnx
    def auxmain(xs): lazy(auxloop(eval(xs)))
    def auxloop(xs):
        match xs:
        for nil: return nil
        for cons(x, xs):
            match filter.test(x):
            for tt: return cons(x, auxmain(xs))
            for ff: return auxloop(eval(xs))
    return auxmain(xs)


@datacon(Stream)
def filter(xs):
    @fnx
    def auxmain(xs):
        return lazy(auxloop(eval(xs)))
    def auxloop(xs):
        match xs as foo:
        for nil: return nil
        for cons(x, xs):
            if filter.test(x):
                return cons(x, auxmain(xs))
            else:
                return auxloop(eval(xs))
        return foo
    return auxmain(xs)


@datacon(Stream)
def filter(xs):
    @fnx
    def auxmain(xs):
        return lazy(auxloop(eval(xs)))
    def auxloop(xs):
        match xs as foo:
        for nil: return nil
        for cons(x, xs):
            if filter.test(x):
                return cons(x, auxmain(xs))
            else:
                return auxloop(eval(xs))
    return auxmain(xs)