[Cython] Fused Types

[Dag Sverre Seljebotn]

On 05/03/2011 10:42 AM, mark florisson wrote:
> On 3 May 2011 10:07, Dag Sverre Seljebotn<d.s.seljebotn at astro.uio.no>  wrote:
>> On 05/03/2011 09:59 AM, mark florisson wrote:
>>>
>>> On 3 May 2011 00:21, Robert Bradshaw<robertwb at math.washington.edu>    wrote:
>>>>
>>>> On Mon, May 2, 2011 at 1:56 PM, mark florisson
>>>> <markflorisson88 at gmail.com>    wrote:
>>>>>
>>>>> On 2 May 2011 18:24, Robert Bradshaw<robertwb at math.washington.edu>
>>>>>   wrote:
>>>>>>
>>>>>> On Sun, May 1, 2011 at 2:38 AM, mark florisson
>>>>>> <markflorisson88 at gmail.com>    wrote:
>>>>>>>
>>>>>>> A remaining issue which I'm not quite certain about is the
>>>>>>> specialization through subscripts, e.g. func[double]. How should this
>>>>>>> work from Python space (assuming cpdef functions)? Would we want to
>>>>>>> pass in cython.double etc? Because it would only work for builtin
>>>>>>> types, so what about types that aren't exposed to Python but can still
>>>>>>> be coerced to and from Python? Perhaps it would be better to pass in
>>>>>>> strings instead. I also think e.g. "int *" reads better than
>>>>>>> cython.pointer(cython.int).
>>>>>>
>>>>>> That's whey we offer cython.p_int. On that note, we should support
>>>>>> cython.astype("int *") or something like that. Generally, I don't like
>>>>>> encoding semantic information in strings.
>>>>>>
>>>>>> OTHO, since it'll be a mapping of some sort, there's no reason we
>>>>>> can't support both. Most of the time it should dispatch (at runtime or
>>>>>> compile time) based on the type of the arguments.
>>>>>
>>>>> If we have an argument type that is composed of a fused type, would be
>>>>> want the indexing to specify the composed type or the fused type? e.g.
>>>>>
>>>>> ctypedef floating *floating_p
>>>>
>>>> How should we support this? It's clear in this case, but only because
>>>> you chose good names. Another option would be to require
>>>> parameterization floating_p, with floating_p[floating] the
>>>> "as-yet-unparameterized" version. Explicit but redundant. (The same
>>>> applies to struct as classes as well as typedefs.) On the other had,
>>>> the above is very succinct and clear in context, so I'm leaning
>>>> towards it. Thoughts?
>>>
>>> Well, it is already supported. floating is fused, so any composition
>>> of floating is also fused.
>>>
>>>>> cdef func(floating_p x):
>>>>>     ...
>>>>>
>>>>> Then do we want
>>>>>
>>>>>     func[double](10.0)
>>>>>
>>>>> or
>>>>>
>>>>>     func[double_p](10.0)
>>>>>
>>>>> to specialize func?
>>>>
>>>> The latter.
>>>
>>> I'm really leaning towards the former. What if you write
>>>
>>> cdef func(floating_p x, floating_p *y):
>>>      ...
>>>
>>> Then specializing floating_p using double_p sounds slightly
>>> nonsensical, as you're also specializing floating_p *.
>>
>> I made myself agree with both of you in turn, but in the end I think I'm
>> with Robert here.
>>
>> Robert's approach sounds perhaps slightly simpler if you think of it this
>> way:
>>
>> ctypedef fused_type(float, double) floating
>> ctypedef floating* floating_p
>>
>> is really a short-hand for
>>
>> ctypedef fused_type(float*, double*) floating_p
>>
>> I.e., when using a fused_type in a typedef you simply get a new fused_type.
>> This sounds in a sense simpler without extra complexity getting in the way
>> ("which was my fused base type again...").
>>
>> Dag SVerre
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>>
>
> Ok, if those typedefs should be disallowed then specialization through
> indexing should then definitely get the types listed in the fused_type
> typedef.

I'm not sure what you mean here. What is disallowed exactly?

DS