Integral operator over Trial/Test functions

Hi everyone,

I'm trying to define the bilinear form defined by

C = (Au, Av)

where u,v are squared-measurable Trial/Test functions over R^2 unit square mesh, my problem is how to define A operator (fredholm integral) over Proxy functions, lets say "(Au)(kx,ky) = Int_{mesh} u(x,y)*G(x,y,kx,ky) dxdy". I would appreciate any ideas.

Best Regards!.