Trac #32625: Parent._is_numerical, _is_real_numerical - remove hard d…

…ependency on real_mpfr, complex_mpfr

This is for '''sagemath-polyhedra''' (#32432), which does not include
the floating point fields

URL: https://trac.sagemath.org/32625
Reported by: mkoeppe
Ticket author(s): Matthias Koeppe
Reviewer(s): Travis Scrimshaw

src/sage/structure/parent.pyx

@@ -2812,9 +2812,16 @@ cdef class Parent(sage.structure.category_object.CategoryObject):
             sage: [R._is_numerical() for R in [RIF, RBF, CIF, CBF]]
             [False, False, False, False]
         """
-        from sage.rings.complex_mpfr import ComplexField
-        from sage.rings.real_mpfr import mpfr_prec_min
-        return ComplexField(mpfr_prec_min()).has_coerce_map_from(self)
+        try:
+            from sage.rings.complex_mpfr import ComplexField
+            from sage.rings.real_mpfr import mpfr_prec_min
+        except ImportError:
+            pass
+        else:
+            return ComplexField(mpfr_prec_min()).has_coerce_map_from(self)
+
+        from sage.rings.real_double import CDF
+        return CDF.has_coerce_map_from(self)
 
     @cached_method
     def _is_real_numerical(self):
@@ -2833,8 +2840,15 @@ cdef class Parent(sage.structure.category_object.CategoryObject):
             sage: [R._is_real_numerical() for R in [RIF, RBF, CIF, CBF]]
             [False, False, False, False]
         """
-        from sage.rings.real_mpfr import RealField, mpfr_prec_min
-        return RealField(mpfr_prec_min()).has_coerce_map_from(self)
+        try:
+            from sage.rings.real_mpfr import RealField, mpfr_prec_min
+        except ImportError:
+            pass
+        else:
+            return RealField(mpfr_prec_min()).has_coerce_map_from(self)
+
+        from sage.rings.real_double import RDF
+        return RDF.has_coerce_map_from(self)
 
 ############################################################################
 # Set base class --