Trac 18358: better pyobject_to_long

src/sage/misc/long.pxd

@@ -4,29 +4,64 @@ Fast conversion macro to long
 
 from libc.limits cimport LONG_MIN
 
-from cpython.int cimport PyInt_CheckExact, PyInt_AS_LONG
-from cpython.long cimport PyLong_CheckExact, PyLong_AsLong
+from cpython.int cimport PyInt_AS_LONG
+from cpython.long cimport PyLong_AsLong
 from cpython.number cimport PyNumber_Index
 
 from sage.libs.gmp.mpz cimport mpz_fits_slong_p, mpz_get_si
 
 from sage.rings.integer cimport Integer
 
-cdef inline long pyobject_to_long(x) except LONG_MIN:
+cdef inline long pyobject_to_long(x) except? LONG_MIN:
     r"""
     Given a Python object ``x`` cast it quickly to a C long.
 
-    If it fails, it either raises a ``TypeError`` or a ``OverflowError`` (and
-    the exceptional value is `LONG_MIN`)
+    A ``TypeError`` is raised if the input can not be converted to an integer or
+    an ``OverflowError`` is raied if it does not fit into a C long.
+
+    TESTS:
+
+    We test indirectly that ``Integer.__pow__`` and ``Rational.__pow__`` work::
+
+        sage: tens = [10r, 10l, 10, 10/1]
+        sage: a = 10
+        sage: a^10
+        10000000000
+        sage: a^(10r)
+        10000000000
+        sage: a^(10l)
+        10000000000
+        sage: a^(10/1)
+        10000000000
+        sage: a^(2**258)
+        Traceback (most recent call last):
+        ...
+        RuntimeError: exponent must be at most 2147483647            # 32-bit
+        RuntimeError: exponent must be at most 9223372036854775807   # 64-bit
+
+        sage: b = 1/2
+        sage: b^10
+        1/1024
+        sage: b^(10r)
+        1/1024
+        sage: b^(10l)
+        1/1024
+        sage: b^(10/1)
+        1/1024
+        sage: b^(2**258)
+        Traceback (most recent call last):
+        ...
+        RuntimeError: exponent must be at most 2147483647            # 32-bit
+        RuntimeError: exponent must be at most 9223372036854775807   # 64-bit
     """
-    if PyInt_CheckExact(x):
+    if isinstance(x, int):
         return PyInt_AS_LONG(x)
     elif type(x) is Integer:
         if mpz_fits_slong_p((<Integer>x).value):
             return mpz_get_si((<Integer>x).value)
         else:
-            raise OverflowError
-    elif PyLong_CheckExact(x):
+            raise OverflowError("Sage Integer too large to convert to C long")
+    elif isinstance(x, long):
         return PyLong_AsLong(x)
 
     return PyNumber_Index(x)