cython_blas does not use const in signatures

Usually, BLAS interfaces for C use function signatures with const qualifiers - examples:

void F77_daxpy( FINT, const double *, const double *, FINT, double *, FINT);

F77_NAME(daxpy)(const int *n, const double *da,
		const double *dx, const int *incx,
		double *dy, const int *incy);

However, the Cython pxd file for cython_blas generates the function signatures without const qualifier:

cdef void daxpy(int *n, d *da, d *dx, int *incx, d *dy, int *incy) nogil

Which makes it harder to wrap into existing programs if they are using const.

[sturlamolden]

https://www.damnyouautocorrect.com I know we have a pandemic and all, but impunity is not immunity…

[sturlamolden]

It should be ok. The compiler will cast T * to const T * but not the other way around. It is the absence of const that cause the problems (i.e. requiring an explicit const_cast of const T * to T * when calling BLAS). Adding const qualifier to the prototypes can be done with impunity. It will only help to solve problems. It should not cause any backwards compatibility issues. In my opinion such a PR would be welcome.