func validateOperator(tokens []LexToken, i int) bool {
	switch tokens[i].value {
	case "*":
		valid := tokens[i-1].typ == tokenSpace ||
			tokens[i-1].typ == tokenSeparator ||
			tokens[i-1].value == "*"
		valid = valid &&
			tokens[i+1].typ == tokenSpace ||
			tokens[i+1].value == "*" ||
			tokens[i+1].typ == tokenSeparator ||
			tokens[i+1].typ == tokenIdentfier ||
			tokens[i+1].value == "="
		if !valid {
			fmt.Printf("%d: '*' not properly formatted\n", tokens[i].linum)
			return false
		}
	}
	return true
}