func (a *Token) Equal(b *Token) bool {
	if a == nil || b == nil {
		return false
	}
	if a.tokenType != b.tokenType {
		return false
	}
	return a.value == b.value
}
func (a *Token) Equal(b *Token) bool {
	if a == nil || b == nil {
		return false
	}
	if a.tokenType != b.tokenType {
		return false
	}
	return a.value == b.value
}
// Equal reports whether tokens a, and b, are equal.
// Two tokens are equal if both their types and values are equal. A nil token can
// never be equal to another token.