[Cython] CF based type inference

[mark florisson]

On 2 June 2013 07:22, Stefan Behnel <stefan_ml at behnel.de> wrote:
> mark florisson, 21.05.2013 15:32:
>> On 21 May 2013 14:14, Vitja Makarov wrote:
>>>
>>> def foo(int N):
>>>     x = 1
>>>     y = 0
>>>     for i in range(N):
>>>         x = x * 0.1 + y * 0.2
>>>         y = x * 0.3 + y * 0.4
>>>     print typeof(x), typeof(y)
>>>
>>> Here both x and y will be inferred as double
>>
>> Ok, so I assume it promotes the incoming types (all reaching
>> definitions)? If N == 0, then when using objects you get an int,
>> otherwise a double.
>
> I'm not sure what you mean here. I certainly don't think the inferred type
> of x and y should depend on the value of N. It should always be a double,
> because that's the spanning type for all paths. In the very unlikely case
> that that's not what the user wants, explicit typing will easily fix it for
> them.

Right, my point is that taking the spanning type of all paths is
different from python semantics. But if you can prove something about
the value of N (e.g. N <= 0, or N > 0), you should certainly exploit
this information.

> Stefan
>
> _______________________________________________
> cython-devel mailing list
> cython-devel at python.org
> http://mail.python.org/mailman/listinfo/cython-devel