Dag Sverre Seljebotn wrote:
> Robert Bradshaw wrote:
>
>> On May 27, 2010, at 12:43 AM, Dag Sverre Seljebotn wrote:
>>
>>
>>
>>> I recognized typeof in a recent commit by Robert. Is this a new
>>> feature
>>> in 0.13 or has it been in for some time?
>>>
>>>
>> It's been around since last fall--I just needed something quick for
>> writing tests for type inference, so typeof was born.
>>
>>
> OK, then this doesn't need to be discussed now at any rate.
>
> I'll just make a quick comment below and then hope the thread dies.
>
>>
>>
>>> If it is new:
>>>
>>> What I'm wondering is whether typeof should perhaps, in the spirit of
>>> Python, return a descriptive object instead of a string. (It could
>>> even
>>> return a ctypes object describing the type, if that is powerful enough
>>> for us).
>>>
>>> In particular, it should be possible to do introspection about structs
>>> and so on, so that it is easy to build serializers etc. using "typeof"
>>> information. (Buffers already put some RTTI about structs to the C
>>> file
>>> BTW, in order to parse buffer format strings.)
>>>
>>> This is thinking long-term; but I'm wondering whether the current
>>> typeof
>>> should be renamed e.g. "nameoftype", in order to maintain backwards
>>> compatability if or when somebody decides to make a more powerful
>>> typeof.
>>>
>>>
>> I was thinking of that at first, but I really can't think of much one
>> would do with it--it's not giving anything that's not known at compile
>> time, it's just a way to make sure the compiler thinks the type is
>> what you think it is. Even with templates, it would return the
>> template parameter, not the resolved type. For testing purposes, a
>> string is very nice.
>>
>>
> cdef persist_struct_to_xml(void* data, object typeinfo, object
> filename): ...
>
> cdef StructA a
> a.b = 2
> a.c = 4
> persist_struct_to_xml(&a, typeof(StructA), 'a.dat')
>
> cdef StructB b
> b.foo = 2
> b.bar = 4.5
> persist_struct_to_xml(&b, typeof(StructB), 'b.dat')
>
Here's a better example that I'd actually find useful now and then:
cdef struct Particle:
double x, y, z, vx, vy, vz
cdef np.ndarray[Particle] arr = np.zeros(100,
dtype=cython_type_to_numpy_dtype(typeof(Particle)))
Dag Sverre
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