Simplified Evaluate function

src/expression/Operator.go

@@ -16,7 +16,7 @@ type Operator struct {
 // Operators defines the operators used in the language.
 // The number corresponds to the operator priority and can not be zero.
 var Operators = [64]Operator{
-	token.Period: {".", 13, 2},
+	token.Dot:    {".", 13, 2},
 	token.Call:   {"λ", 12, 1},
 	token.Array:  {"@", 12, 2},
 	token.Negate: {"-", 11, 1},