Merge pull request #439 from skirpichev/fix-mpf-inf

Correct mpf initialization from tuple for f(n)inf

mpmath/ctx_mp_python.py

@@ -67,9 +67,11 @@ class _mpf(mpnumeric):
                 v._mpf_ = from_man_exp(val[0], val[1], prec, rounding)
                 return v
             if len(val) == 4:
-                sign, man, exp, bc = val
+                if val not in (finf, fninf, fnan):
+                    sign, man, exp, bc = val
+                    val = normalize(sign, MPZ(man), exp, bc, prec, rounding)
                 v = new(cls)
-                v._mpf_ = normalize(sign, MPZ(man), exp, bc, prec, rounding)
+                v._mpf_ = val
                 return v
             raise ValueError
         else:

mpmath/tests/test_basic_ops.py

@@ -443,3 +443,9 @@ def test_isnan_etc():
     assert mp.isnpint(-1.1+0j) == False
     assert mp.isnpint(-1+0.1j) == False
     assert mp.isnpint(0+0.1j) == False
+
+
+def test_issue_438():
+    assert mpf(finf) == mpf('inf')
+    assert mpf(fninf) == mpf('-inf')
+    assert mpf(fnan)._mpf_ == mpf('nan')._mpf_