On Sunday, May 8, 2016 at 1:10:44 PM UTC-7, Max Külshammer wrote:
>
> Thanks for answering! I was in holiday. Now I tested:
>
> %cython
>
> from sage.rings.integer cimport Integer
>
> cpdef int W():
> cdef Integer x = 5
> cdef Integer y = 2
> if x._is_power_of(y) == True:
> print 'yes'
> return 1
>
> It looks like the "typecast" from "int" to "Integer" is not picked up
automatically, so you have to spell it out:
cdef Integer x = Integer(5)
Oddly enough, it does work in other situations. If you write
cdef Integer x = Integer(5)+1
it will figure out how to convert the "1" to be an Integer (the conversion
and addition will still be performed at runtime, though, because the C
compiler cannot be expected to fold "constants" through user-defined types).
so this might actually be an issue in cython that can be improved: insert
better code convert type of rvalue to that of the lvalue.
> But got the error:
>
> Exception TypeError: 'Cannot convert int to sage.rings.integer.Integer'
>
> Any ideas?
> Max
>
>
>
>
> Am Montag, 2. Mai 2016 10:47:23 UTC+2 schrieb Simon King:
>>
>> Hi Max,
>>
>> On 2016-05-01, Max Külshammer <[email protected]> wrote:
>> > I would like to use a sage function (is_power_of) in an cython program
>> I am
>> > writing (via %cython in SMC). To speed things up I would like to import
>> the
>> > c version of is_power_of which can be found
>> > in
>> https://github.com/sagemath/sage/blob/master/src/sage/rings/integer.pyx#L4271
>>
>> > as
>> https://github.com/sagemath/sage/blob/master/src/sage/rings/integer.pxd#L26.
>>
>> >
>> > Can someone explain how I import such an function into cython? My
>> failed
>> > attemps look like this:
>> >
>> > %cython
>> > from libc.math cimport log
>> > cimport integer
>> > from integer cimport _is_power_of
>>
>> _is_power_of is a method of the extension class "Integer". Hence, when
>> doing
>> from sage.rings.integer cimport Integer
>> and then have something like
>> cdef Integer x = 5
>> in your code, then you can do
>> x._is_power_of(2)
>>
>> Best regards,
>> Simon
>>
>>
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