cwrapper module [WIP]

[ivan-pi]

I believe I now have a complete interface to the routines in <cwrapper.h>. To ease the task I have leveraged fypp to do part of the work. I've also used fypp for conditional compilation, meaning that commands such as:

fypp -DHAVE_SYMENGINE_LLVM symengine_cwrapper.fypp symengine_cwrapper.f90

are needed. This also means the flags from the C++ SymEngine build need to be somehow propagated to the Fortran version.

I still need to create the unit tests to make sure that my type translations are correct:

C	Fortran
basic s	type(c_ptr) :: s	This is because of typedef basic_struct basic[1]; which is used to force reference semantics
const basic s	type(c_ptr), intent(in) :: s
char * (returned value)	type(c_ptr)
const char *str (input value)	character(c_char), intent(in) :: str(*)
size_t n	integer(c_size_t), value :: n
int i	integer(c_int), value :: i
unsigned i	integer(c_int), value :: i
long i	integer(c_long), value :: i
unsigned long i	integer(c_long), value :: i
CWRAPPER_OUTPUT_TYPE	type(c_ptr)
float f	real(c_float), value :: f
double d	real(c_double), value :: d
CVecBasic *self	type(c_ptr) :: self
CDenseMatrix *self	type(c_ptr) :: self
CSparseMatrix *self	type(c_ptr) :: self
CSetBasic *self	type(c_ptr) :: self
CMapBasicBasic *self	type(c_ptr) :: self

@certik Do you think unit tests are needed on the level of the C interface (where we work explicitly with the handles to type(c_ptr)) or would it suffice to have tests of the higher level interface (still to be developed)?

My current plan was to adapt the tests found in test_cwrapper.c of SymEngine. I won't be able to make progress that fast, but thought I will just create a PR if anyone else would like to contribute to my fork.

[certik]

Awesome, great job!

I think we don't need to thoroughly test the low level interface, if we test the high level (to be written) interface and it works, that should robustly test the low level interface also.

Let me know if you need any help with this.