[Cython] wrapping c++

[William Stein]

On Tue, Mar 4, 2008 at 6:39 AM, Neal Becker <ndbecker2 at gmail.com> wrote:
> I've made some progress on learning to wrap std::vector.  I've got a
>  __getitem__, but I don't know what to do about __setitem__.
>  cdef extern from "vector":
>     pass
>
>  cdef extern from "test1.hpp":
>     ctypedef struct intvec "std::vector<unsigned int>":
>         void (* push_back)(int elem)
>         inline int get "operator[]" (int i)
>
>     intvec intvec_factory "std::vector<unsigned int>"(int len)
>
>     int my_sum "my_sum<std::vector<unsigned int> >"(intvec vec)
>
>
>
>  cdef intvec v = intvec_factory(2)
>  v.push_back(2)
>
>  #print my_sum (v)
>
>  cdef class intvec_wrap:
>     cdef intvec vec
>     def __init__(self):
>         self.vec = intvec_factory (2)
>     def __getitem__(self, int i):
>         return self.vec.get (i)
>
>  Problem is, operator[] (or at()) returns an int&.  I don't have a clue what
>  to do with this.

There is an example of doing setitem directly in Cython with
std::vector<unsigned int>
using C name specifiers in my talk on Cython at Enthought from two
days ago.  See
the talk listed at the bottom of this page:
  http://wiki.sagemath.org/days8/schedule

Here's the example:

cdef extern from "vector.h":
    ctypedef unsigned long size_type

    ctypedef struct intvec "std::vector<unsigned int>":
        int get_entry "operator[]"(int n)
        size_type size()

    intvec intvec_factory "std::vector<unsigned int>"(int len)

cdef extern from "":
    void DEFINE_SET "#define SET(a,b,c) a[b]=c; //"()
    void SET(intvec, int, int)
DEFINE_SET()


cdef intvec v = intvec_factory(10)
SET(v,2,5)
print v.get_entry(2)
print v.size()


----------------

The key thing is the evil dirty trick to define a SET macro directly in Cython.
 -- William