C[omp]ute

From: andrew cooke <andrew@...>

Date: Fri, 29 Apr 2011 22:28:21 -0300

This is a draft, and the pytyp library it describes is not the one available
for download (although it is in hg on Google code), but I wanted to put it out
there in case anyone had any comments (which would be MUCH appreciated)

I think it's pretty cool.  It's a DSL for Python that integrates with ABCs to
extend Python's types.  Some examples:

    >>> isinstance(5, Or(int, str))
    True
    >>> isinstance("five", Or(int, str))
    True

    >>> @checked
    ... def int_list_len(s:[int]) -> int:
    ...     return len(s)
    >>> int_list_len([1,2,3])
    3
    >>> int_list_len('abc')
    Traceback (most recent call last):
      ...
    TypeError: Type Seq(int) inconsistent with 'abc'.

    >>> class Foo:
    ...     def __init__(self, x):
    ... 	self.x = x
    >>> ifoo = Foo(1)
    >>> sfoo = Foo('one')
    >>> assert isinstance(ifoo, Foo)
    >>> assert isinstance(sfoo, Cls(Foo))
    >>> assert isinstance(ifoo, And(Foo, Atr(x=int)))
    >>> assert not isinstance(sfoo, And(Foo, Atr(x=int)))

Anyway, the paper is at http://www.acooke.org/pytyp.pdf

Andrew

PS If you are reading this post in the future (woot!  flying cars!) then I may
have replaced the link with a more up-to-date version, and updated the
library, of course.