* \param compar_fn comparison function of type (int (compar_fn*) (void*) (void*)).
*
* Remark: if the elements stored in the dynar are structures, the compar_fn
* \param compar_fn comparison function of type (int (compar_fn*) (void*) (void*)).
*
* Remark: if the elements stored in the dynar are structures, the compar_fn