Merge pull request #99 from oscarbenjamin/pr_pypy_fix

Fix test failures under PyPy

src/flint/test/test.py

@@ -3,6 +3,7 @@
 import operator
 import pickle
 import doctest
+import platform
 
 from flint.utils.flint_exceptions import DomainError
 
@@ -11,6 +12,8 @@
 if sys.version_info[0] >= 3:
     long = int
 
+PYPY = platform.python_implementation() == "PyPy"
+
 ctx = flint.ctx
 
 def raises(f, exception):
@@ -141,13 +144,17 @@ def test_fmpz():
     for a, b, c, ab_mod_c in pow_mod_examples:
         assert pow(a, b, c) == ab_mod_c
         assert pow(flint.fmpz(a), b, c) == ab_mod_c
-        assert pow(a, flint.fmpz(b), c) == ab_mod_c
-        assert pow(a, b, flint.fmpz(c)) == ab_mod_c
         assert pow(flint.fmpz(a), flint.fmpz(b), c) == ab_mod_c
         assert pow(flint.fmpz(a), b, flint.fmpz(c)) == ab_mod_c
-        assert pow(a, flint.fmpz(b), flint.fmpz(c)) == ab_mod_c
         assert pow(flint.fmpz(a), flint.fmpz(b), flint.fmpz(c)) == ab_mod_c
 
+        # 3-arg pow cannot be made to work with fmpz on PyPy
+        # https://github.com/flintlib/python-flint/issues/74
+        if not PYPY:
+            assert pow(a, flint.fmpz(b), c) == ab_mod_c
+            assert pow(a, b, flint.fmpz(c)) == ab_mod_c
+            assert pow(a, flint.fmpz(b), flint.fmpz(c)) == ab_mod_c
+
     assert raises(lambda: pow(flint.fmpz(2), 2, 0), ValueError)
     # XXX: Handle negative modulus like int?
     assert raises(lambda: pow(flint.fmpz(2), 2, -1), ValueError)

src/flint/types/fmpz_mod_poly.pyx

@@ -880,6 +880,9 @@ cdef class fmpz_mod_poly(flint_poly):
         """
         return self[0]
 
+    # XXX: Methods like leading_coefficient() that are generic should be moved
+    # to the flint_poly base class rather than defined here.
+
     def leading_coefficient(self):
         """
         Return the leading coefficient of this polynomial.
@@ -889,6 +892,12 @@ cdef class fmpz_mod_poly(flint_poly):
             >>> f.leading_coefficient()
             fmpz_mod(3, 163)
         """
+        # XXX: This is a workaround for a Cython/PyPy bug:
+        # https://github.com/flintlib/python-flint/issues/74
+        # https://github.com/cython/cython/issues/5776
+        d = self.degree()
+        if d < 0:
+            return self.ctx.mod.zero()
         return self[self.degree()]
 
     def reverse(self, degree=None):