3 ms·

It seems you're just counting ocurrences? The Multiset actually stores them IIRC. So to me it seems the Set type should be map[string][]type_of_elem, if that i

by swah 14y ago

It seems you're just counting ocurrences? The Multiset actually stores them IIRC. So to me it seems the Set type should be map[string][]type_of_elem, if that is possible. [edit] I'm confusing Multiset with Multimap... sorry. [note] Actually Multimap/Mutliset is not shipped with Java, but from Google... So it's not that "included".

burntsushi 14y ago
> It seems you're just counting ocurrences? Yeah. Remember, a multi-set is just a bag. If the bag is `{a, b, a, a, b}`, then it can also be represented as a simple frequency vector: `{a: 3, b: 2}`. There's no need to actually store duplicate values. > So to me it seems the Set type should be map[string][]type_of_elem, if that is possible. OK, now I see. It depends on what your definition of equality is. If the entire value represents identity, then my solution works. But if only part of your value (say, some but not all fields in a struct) represents identity, then my approach won't work at all. My approach relies on Go's built in definition of equality, which isn't flexible and cannot be changed. For instance, if you're storing values with this type in your set: type MyValue struct { Id int Tag string } And these two values are equivalent: MyValue{5, "abc"} MyValue{5, "xyz"} Then you'd have to roll your own implementation. (Since in the eyes of Go, these two values are not equal. And that cannot be changed.) There are elegant ways around this, but it is certainly more clumsy in Go than it would be in a language with some sort of ad hoc polymorphism (like overloading in Java or type classes in Haskell). I think your idea is pretty close: type MultiSet map[MyValueIdentity][]MyValue type MyValueIdentity int Anyway, best of luck to you. Don't be afraid to drop by the #go-nuts channel on IRC. We're a friendly bunch :-)

by swah 14y ago

burntsushi 14y ago

> It seems you're just counting ocurrences? Yeah. Remember, a multi-set is just a bag. If the bag is `{a, b, a, a, b}`, then it can also be represented as a simple frequency vector: `{a: 3, b: 2}`. There's no need to actually store duplicate values. > So to me it seems the Set type should be map[string][]type_of_elem, if that is possible. OK, now I see. It depends on what your definition of equality is. If the entire value represents identity, then my solution works. But if only part of your value (say, some but not all fields in a struct) represents identity, then my approach won't work at all. My approach relies on Go's built in definition of equality, which isn't flexible and cannot be changed. For instance, if you're storing values with this type in your set: type MyValue struct { Id int Tag string } And these two values are equivalent: MyValue{5, "abc"} MyValue{5, "xyz"} Then you'd have to roll your own implementation. (Since in the eyes of Go, these two values are not equal. And that cannot be changed.) There are elegant ways around this, but it is certainly more clumsy in Go than it would be in a language with some sort of ad hoc polymorphism (like overloading in Java or type classes in Haskell). I think your idea is pretty close: type MultiSet map[MyValueIdentity][]MyValue type MyValueIdentity int Anyway, best of luck to you. Don't be afraid to drop by the #go-nuts channel on IRC. We're a friendly bunch :-)