Compiled callback function

Idea: if callback formula is a string, we could embed it in a Fortran function and call Fortran instead of Python

F2PY has a module for ``inline'' Fortran code specification and building

source = """
      real*8 function fcb(x, y)
      real*8 x, y
      fcb = %s
      return
      end
""" % fstr
import f2py2e
f2py_args = "--fcompiler='Gnu' --build-dir tmp2 etc..."
f2py2e.compile(source, modulename='callback',
               extra_args=f2py_args, verbose=True,
               source_fn='sourcecodefile.f')
import callback
<work with the new extension module>