Merge pull request #16745 from smichr/logneginf

log(-oo) -> oo + I*pi
2019-04-28 01:13:26 -05:00 · 2019-04-27 14:14:38 -05:00 · 2019-04-27 11:07:14 -05:00
2 changed files with 10 additions and 8 deletions
@@ -544,14 +544,15 @@ class log(Function):
            elif arg is S.Infinity:
                return S.Infinity
            elif arg is S.NegativeInfinity:
-                return S.Infinity
+                return S.Infinity + S.Pi*S.ImaginaryUnit
            elif arg is S.NaN:
                return S.NaN
            elif arg.is_Rational and arg.p == 1:
                return -cls(arg.q)

        if arg is S.ComplexInfinity:
-                return S.ComplexInfinity
+            return S.ComplexInfinity
+
        if isinstance(arg, exp) and arg.args[0].is_real:
            return arg.args[0]
        elif isinstance(arg, exp_polar):
@@ -563,12 +564,9 @@ class log(Function):
                return
        elif isinstance(arg, SetExpr):
            return arg._eval_func(cls)
-
-        if arg.is_number:
+        elif arg.is_number:
            if arg.is_negative:
-                return S.Pi * S.ImaginaryUnit + cls(-arg)
-            elif arg is S.ComplexInfinity:
-                return S.ComplexInfinity
+                return S.Pi*S.ImaginaryUnit + cls(-arg)
            elif arg is S.Exp1:
                return S.One

@@ -147,9 +147,13 @@ def test_exp_MatrixSymbol():

 def test_log_values():
    assert log(nan) == nan
+    assert log(float('nan')) == nan

    assert log(oo) == oo
-    assert log(-oo) == oo
+    assert log(float('inf')) == oo
+
+    assert log(-oo) == oo + I*pi
+    assert log(float('-inf')) == oo + I*pi

    assert log(zoo) == zoo
    assert log(-zoo) == zoo