test_cexp :: CDouble -> CDouble -> IO CDouble
test_cexp x y =
  [C.exp| double{ cos($(double x)) + cos($(double y)) } |]
test_cexp :: CDouble -> CDouble -> IO CDouble
test_cexp x y =
  [C.exp| double{ cos($(double x)) + cos($(double y)) } |]
test_cexp x y =
  [C.exp| double{ cos($(double x)) + cos($(double y)) } |]