core: add power operator "**" in calc expressions (issue #997)

src/core/wee-calc.c

@@ -73,7 +73,8 @@ calc_operator_precedence (char *operator)
     if ((strcmp (operator, "*") == 0)
         || (strcmp (operator, "/") == 0)
         || (strcmp (operator, "//") == 0)
-        || (strcmp (operator, "%") == 0))
+        || (strcmp (operator, "%") == 0)
+        || (strcmp (operator, "**") == 0))
     {
         return 2;
     }
@@ -135,6 +136,9 @@ calc_operation (char *operator, double value1, double value2)
     if (strcmp (operator, "%") == 0)
         return (value2 != 0) ? fmod (value1, value2) : 0;
 
+    if (strcmp (operator, "**") == 0)
+        return pow (value1, value2);
+
     return 0;
 }
 
@@ -217,12 +221,13 @@ calc_format_result (double value, char *result, int max_size)
  * Calculates an expression, which can contain:
  *   - integer and decimal numbers (ie 2 or 2.5)
  *   - operators:
- *       +: addition
- *       -: subtraction
- *       *: multiplication
- *       /: division
- *       \: division giving an integer as result
- *       %: remainder of division
+ *        +: addition
+ *        -: subtraction
+ *        *: multiplication
+ *        /: division
+ *        \: division giving an integer as result
+ *        %: remainder of division
+ *       **: power
  *   - parentheses: ( )
  *
  * The value returned is a string representation of the result, which can be

src/core/wee-command.c

@@ -7366,7 +7366,7 @@ command_init ()
            "  12. a ternary operator (format: "
            "\"if:condition?value_if_true:value_if_false\")\n"
            "  13. result of an expression with parentheses and operators "
-           "+ - * / // % (format: \"calc:xxx\")\n"
+           "+ - * / // % ** (format: \"calc:xxx\")\n"
            "  14. an option (format: \"file.section.option\")\n"
            "  15. a local variable in buffer\n"
            "  16. a hdata name/variable (the value is automatically converted "