Conversion to gmpy types

[isuruf]

SymEngine should use the gmpy C API for conversion

[certik]

What do we do now?

[rwst]

cdef class Rational(Number):
...
    def _sympy_(self):
        rat = self.get_num_den()
        return rat[0]._sympy_() / rat[1]._sympy_()

cdef class Integer(Number):
...
    def _sympy_(self):
        import sympy
        return sympy.Integer(deref(self.thisptr).__str__().decode("utf-8"))

[rwst]

What about this snippet in the sympy.Rational constructor?

            if not isinstance(p, SYMPY_INTS + (Rational,)):
                raise TypeError('invalid input: %s' % p)

[rwst]

Ah ok, in compatibility.py:

if GROUND_TYPES == 'gmpy':
    SYMPY_INTS += (type(gmpy.mpz(0)),)