That feature really helps when you use integers for indexing, e.g., like an enum. Say you are parsing a file format with a type field which can have values 5, 6

That feature really helps when you use integers for indexing, e.g., like an enum. Say you are parsing a file format with a type field which can have values 5, 6, 7, you can easily check if that's valid with a single call and lookup something, like a corresponding length in an array without having to translate those field values to array indices first.