[gnome-calculator] Use _ instead of ans for last result (bgo#785107)

[Robert Roth <robertroth src gnome org>]

commit ad694dba6d13633bb5a2ec6f41b3a3fe9758007d
Author: Robert Roth <robert roth off gmail com>
Date:   Sun Sep 17 00:35:46 2017 +0300

    Use _ instead of ans for last result (bgo#785107)

 help/C/variables.page          |    2 +-
 lib/math-equation.vala         |   18 +++++++++---------
 src/math-variable-popover.vala |    6 +++---
 3 files changed, 13 insertions(+), 13 deletions(-)
---
diff --git a/help/C/variables.page b/help/C/variables.page
index 47c9f43..9fdf71a 100644
--- a/help/C/variables.page
+++ b/help/C/variables.page
@@ -37,7 +37,7 @@
     </p>
     <table>
     <tr>
-    <td><p>ans</p></td>
+    <td><p>_</p></td>
     <td><p>Result of previous calculation</p></td>
     </tr>
     <tr>
diff --git a/lib/math-equation.vala b/lib/math-equation.vala
index cfd7b8e..bb9c771 100644
--- a/lib/math-equation.vala
+++ b/lib/math-equation.vala
@@ -661,11 +661,11 @@ public class MathEquation : Gtk.SourceBuffer
         get
         {
             /* Check if the previous answer is before start of error token.
-             * If so, subtract 3 (the length of string "ans") and add actual answer length (ans_end - 
ans_start) into it. */
+             * If so, subtract 1 (the length of string "_") and add actual answer length (ans_end - 
ans_start) into it. */
             int ans_start, ans_end;
             get_ans_offsets (out ans_start, out ans_end);
             if (ans_start != -1 && ans_start < state.error_token_start)
-                return state.error_token_start + ans_end - ans_start - 3;
+                return state.error_token_start + ans_end - ans_start - 1;
 
             return state.error_token_start;
         }
@@ -676,11 +676,11 @@ public class MathEquation : Gtk.SourceBuffer
         get
         {
             /* Check if the previous answer is before end of error token.
-             * If so, subtract 3 (the length of string "ans") and add actual answer length (ans_end - 
ans_start) into it. */
+             * If so, subtract 1 (the length of string "_") and add actual answer length (ans_end - 
ans_start) into it. */
             int ans_start, ans_end;
             get_ans_offsets (out ans_start, out ans_end);
             if (ans_start != -1 && ans_start < state.error_token_end)
-                return state.error_token_end + ans_end - ans_start - 3;
+                return state.error_token_end + ans_end - ans_start - 1;
 
             return state.error_token_end;
         }
@@ -693,7 +693,7 @@ public class MathEquation : Gtk.SourceBuffer
 
     public bool is_result
     {
-        get { return equation == "ans"; }
+        get { return equation == "_"; }
     }
 
     public string equation
@@ -707,7 +707,7 @@ public class MathEquation : Gtk.SourceBuffer
             if (ans_start_mark != null)
                 get_ans_offsets (out ans_start, out ans_end);
             if (ans_start >= 0)
-                text = text.splice (text.index_of_nth_char (ans_start), text.index_of_nth_char (ans_end), 
"ans");
+                text = text.splice (text.index_of_nth_char (ans_start), text.index_of_nth_char (ans_end), 
"_");
 
             var last_is_digit = false;
             var index = 0;
@@ -1063,7 +1063,7 @@ public class MathEquation : Gtk.SourceBuffer
             return;
 
         /* If showing a result return to the equation that caused it */
-        // FIXME: Result may not be here due to solve (i.e. the user may have entered "ans")
+        // FIXME: Result may not be here due to solve (i.e. the user may have entered "_")
         if (is_result)
         {
             undo ();
@@ -1388,7 +1388,7 @@ private class MEquation : Equation
     {
         var lower_name = name.down ();
 
-        if (lower_name == "rand" || lower_name == "ans")
+        if (lower_name == "rand" || lower_name == "_")
             return true;
 
         return m_equation.variables.get (name) != null;
@@ -1400,7 +1400,7 @@ private class MEquation : Equation
 
         if (lower_name == "rand")
             return new Number.random ();
-        else if (lower_name == "ans")
+        else if (lower_name == "_")
             return m_equation.answer;
         else
             return m_equation.variables.get (name);
diff --git a/src/math-variable-popover.vala b/src/math-variable-popover.vala
index c9837e0..17c2f87 100644
--- a/src/math-variable-popover.vala
+++ b/src/math-variable-popover.vala
@@ -11,7 +11,7 @@
 [GtkTemplate (ui = "/org/gnome/calculator/math-variable-popover.ui")]
 public class MathVariablePopover : Gtk.Popover
 {
-    private static string[] RESERVED_VARIABLE_NAMES = {"ans", "rand"};
+    private static string[] RESERVED_VARIABLE_NAMES = {"_", "rand"};
 
     private MathEquation equation;
 
@@ -55,8 +55,8 @@ public class MathVariablePopover : Gtk.Popover
 
     private void handler (string answer, Number number, int number_base, uint representation_base)
     {
-        variable_list.remove (find_row_for_variable ("ans"));
-        variable_list.add (make_variable_row ("ans", number));
+        variable_list.remove (find_row_for_variable ("_"));
+        variable_list.add (make_variable_row ("_", number));
     }
 
     private Gtk.ListBoxRow? find_row_for_variable (string name)