Yes, as I said, if you use a map[T]bool, you need to use something like: for k, v := range m { if v { } } But it also allows you to use "if m[key] { .

Yes, as I said, if you use a map[T]bool, you need to use something like: for k, v := range m { if v { } } But it also allows you to use "if m[key] { ... }". It is literally a trade-off for what convenience you want. And in both cases, you should (probably) wrap an abstraction around the raw map.