[cffi-devel] mem-aref and complex numbers

[Luís Oliveira]

On Sun, Aug 16, 2009 at 5:14 PM, Tamas K Papp<tkpapp at gmail.com> wrote:
> Is there a way to make mem-aref work with CL's complex numbers?  I
> don't need anything else from CFFI (no complex function arguments, return
> types, etc), just mem-aref, eg something like
>
> (mem-aref ptr :complex-float 11)

That is doable with something like:

(defmethod translate-from-foreign (ptr (type complex-float-type))
  (complex (mem-aref ptr :float 0) (mem-aref ptr :float 1)))


> (setf (mem-aref ptr :complex-float 12) #C(1s0 2s0))

But that isn't. Would defining your own setter work for you?

(defun complex-float-aref (ptr index c)
  (let ((p (* (foreign-type-size :complex-float) index)))
    (setf (mem-aref p :float 0) (realpart c)
            (mem-aref p :float 1) (imagpart c))))

To do that with plain MEM-AREF as you wanted, I think we would need
some sort of TRANSLATE-INTO-FOREIGN hook.

HTH.

-- 
Luís Oliveira
http://student.dei.uc.pt/~lmoliv/