Fix exponent operator precedence

Now -2^2 == -4

Author: antonmedv

parser/parser.go

@@ -31,8 +31,8 @@ type builtin struct {
 var unaryOperators = map[string]operator{
 	"not": {50, left},
 	"!":   {50, left},
-	"-":   {500, left},
-	"+":   {500, left},
+	"-":   {90, left},
+	"+":   {90, left},
 }
 
 var binaryOperators = map[string]operator{
@@ -58,7 +58,7 @@ var binaryOperators = map[string]operator{
 	"*":          {60, left},
 	"/":          {60, left},
 	"%":          {60, left},
-	"**":         {70, right},
+	"**":         {100, right},
 }
 
 var builtins = map[string]builtin{

parser/parser_test.go

@@ -59,6 +59,17 @@ func TestParse(t *testing.T) {
 			"-3",
 			&ast.UnaryNode{Operator: "-", Node: &ast.IntegerNode{Value: 3}},
 		},
+		{
+			"-2**2",
+			&ast.UnaryNode{
+				Operator: "-",
+				Node: &ast.BinaryNode{
+					Operator: "**",
+					Left:     &ast.IntegerNode{Value: 2},
+					Right:    &ast.IntegerNode{Value: 2},
+				},
+			},
+		},
 		{
 			"1 - 2",
 			&ast.BinaryNode{Operator: "-", Left: &ast.IntegerNode{Value: 1}, Right: &ast.IntegerNode{Value: 2}},