[gnome-calculator] Fixes #756960 e^(-0.5) returned the wrong value

[Alberto Ruiz <aruiz src gnome org>]

commit 5722513a0bb1903f5602a55dcfbb1ac7013003aa
Author: Felix Pelletier <felixpelletier23 gmail com>
Date:   Sun Jan 10 19:36:44 2016 +0000

    Fixes #756960 e^(-0.5) returned the wrong value

 lib/number.vala          |    2 +-
 tests/test-equation.vala |    1 +
 2 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/lib/number.vala b/lib/number.vala
index 0b09248..52475e9 100644
--- a/lib/number.vala
+++ b/lib/number.vala
@@ -507,7 +507,7 @@ public class Number : Object
         if (!y.is_integer ())
         {
             var reciprocal = y.reciprocal ();
-            if (reciprocal.is_integer ())
+            if (reciprocal.is_integer () && !reciprocal.is_negative())
                 return root (reciprocal.to_integer ());
             else
                 return pwr (y);
diff --git a/tests/test-equation.vala b/tests/test-equation.vala
index 80b3898..bde8e9e 100644
--- a/tests/test-equation.vala
+++ b/tests/test-equation.vala
@@ -425,6 +425,7 @@ private void test_equations ()
     test ("2^0.5", "1.414213562", 0);
     test ("₃√−8", "−2", 0);
     test ("(−8)^(1÷3)", "−2", 0);
+    test ("e^(−0.5)", "0.60653066", 0);
 
     test ("0 mod 7", "0", 0);
     test ("6 mod 7", "6", 0);