[gnome-calculator] Define 'pi' variable (refs #153)

[Robert Roth <robertroth src gnome org>]

commit f8bb81ccd279fbc95c6c4c59c517f51a9808145b
Author: Robert Roth <robert roth off gmail com>
Date:   Thu Jun 4 13:04:29 2020 +0300

    Define 'pi' variable (refs #153)

 lib/equation.vala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/lib/equation.vala b/lib/equation.vala
index d5ab0f3d..50fda3a7 100644
--- a/lib/equation.vala
+++ b/lib/equation.vala
@@ -166,7 +166,7 @@ private class EquationParser : Parser
     protected override bool variable_is_defined (string name)
     {
         /* FIXME: Make more generic */
-        if (name == "e" || name == "i" || name == "π")
+        if (name == "e" || name == "i" || name == "π" || name == "pi")
             return true;
 
         return equation.variable_is_defined (name);
@@ -178,7 +178,7 @@ private class EquationParser : Parser
             return new Number.eulers ();
         else if (name == "i")
             return new Number.i ();
-        else if (name == "π")
+        else if (name == "π" || name == "pi")
             return new Number.pi ();
         else
             return equation.get_variable (name);