Adding Support for Indices

- Adding token ^
- Updating order of operation to include indices
- Adding action for new #indices (using php pow function)
- NB, tests delayed since it appears the suite is already failing?

Author: carlbateson

Arithmetic.pp

@@ -49,6 +49,7 @@
 %token  minus     \-|−
 %token  times     \*|×
 %token  div       /|÷
+%token  indices   \^
 %token  constant  [A-Z_]+[A-Z0-9_]*
 %token  id        \w+
 
@@ -62,7 +63,10 @@
     ternary() ( ::times:: #multiplication expression() )?
 
 ternary:
-    term() ( ::div:: #division expression() )?
+    quaternary() ( ::div:: #division expression() )?
+
+quaternary:
+    term() ( ::indices:: #indices expression() )?
 
 term:
     ( ::bracket_:: expression() ::_bracket:: #group )

Visitor/Arithmetic.php

@@ -177,6 +177,17 @@ public function visit(
 
                 break;
 
+            case '#indices':
+                $children[0]->accept($this, $a, $eldnah);
+
+                $acc = function ($b) use ($a, $acc) {
+                    return $acc(pow($a(), $b));
+                };
+
+                $children[1]->accept($this, $acc, $eldnah);
+
+                break;
+
             case '#division':
                 $children[0]->accept($this, $a, $eldnah);
                 $parent = $element->getParent();