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The simplest example I can think of is: Map(slice, func) You can can implement this generically in Go using interface{} types and runtime type checking, but th

The simplest example I can think of is: Map(slice, func) You can can implement this generically in Go using interface{} types and runtime type checking, but then you have runtime type checking failures. A java/c++-esque "generics" implementation would be able to type-check at compile time.

ori_b 7y ago
You can implement it in Go using loops, and it's not significantly slower or more error prone.
- hauleth 7y ago
  Unless you want to implement that on top of your custom structure, like, for example, b-tree. Then you either need to write N different implementations for each separate tree or you need to use `interface{}`.
  - ori_b 7y ago
    Yes, custom containers are one place that generics are very useful. Go has the most useful containers built in. Most code I write doesn't need custom containers, even in languages with templates (I write far more C++ and Java than Go) -- so I find that I don't miss them much when I spend time in Gopherspace.
    - NoodleIncident 7y ago
      The most egregious missing container is "set", coming from Python (as many Go developers do). After debugging, reviewing, and writing at least 3 different local implementations of a set, I can't wait for generics so that it can be written once and then never looked at again.
      - mappu 7y ago
        I'm slightly surprised you found three different set implementations - `map[T]struct{}` is the idiomatic one i see everywhere. I suppose it's not sorted or concurrent-safe?
        NoodleIncident 7y ago
        I mean that people make their own per-file or per-package set implementation for their service. There's no point putting it in a common utility package even within the same company, because it's specific to the type of what they're storing. `map[T]struct{}` is only a type, it's not an implementation. You still need a handful of methods, that might be named inconsistently in each implementation by different developers. I will be happy when I never have to think about this again
        masklinn 7y ago
        > I'm slightly surprised you found three different set implementations - `map[T]struct{}` is the idiomatic one i see everywhere. Set storage is not really the concern here, it's the set-theoretic operations which make sets useful (generally speaking, there are cases where all you need is the set being a set e.g. deduplication). So I wouldn't be surprised that GP found several different implementations of union, intersection, difference, symmetric difference, subset, superset, …
- crimsonalucard 7y ago
  Yeah but you can't implement it generically. That means for every conceivable input type and output type combination you have to have a new MAP or REDUCE function to handle it. All Modern languages except golang and elm only require one implementation of MAP that can handle all type combinations. It's called parametric polymorphism.
  - ori_b 7y ago
    Yes, I know what it's called. I have implemented generics in compilers. I still don't miss them in most go code, in practice.
  - vbezhenar 7y ago
    Java is one example of modern language without proper generics. They have syntax sugar for Object references, but you can do almost the same with golang using interface{}.
    - excursionist 7y ago
      I'm not sure what you mean by 'proper generics', but Java does have compile-time generics, ie List<T>, <A, B> B foo(A bar), etc.
      - vbezhenar 7y ago
        Proper generics would allow you to parameterize with all types including primitive ones, not just Objects. Check out java.util.Arrays class as an example of why Java's generics are not proper: https://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html https://docs.oracle.com/javase/7/docs/api/java/util/Arrays.h...
        leshow 7y ago
        You've got a kind of made up definition of 'proper'. Java has generics, they don't have the best implementation of it I've seen, but I wouldn't call it 'improper'. It's just not a word that has any specific meaning in this context. I seem to remember an article being written a while ago that found Java's type system, with the addition of generics, was unsound. Maybe that's what you're trying to say.

ori_b 7y ago

You can implement it in Go using loops, and it's not significantly slower or more error prone.

hauleth 7y ago
Unless you want to implement that on top of your custom structure, like, for example, b-tree. Then you either need to write N different implementations for each separate tree or you need to use `interface{}`.
- ori_b 7y ago
  Yes, custom containers are one place that generics are very useful. Go has the most useful containers built in. Most code I write doesn't need custom containers, even in languages with templates (I write far more C++ and Java than Go) -- so I find that I don't miss them much when I spend time in Gopherspace.
  - NoodleIncident 7y ago
    The most egregious missing container is "set", coming from Python (as many Go developers do). After debugging, reviewing, and writing at least 3 different local implementations of a set, I can't wait for generics so that it can be written once and then never looked at again.
    - mappu 7y ago
      I'm slightly surprised you found three different set implementations - `map[T]struct{}` is the idiomatic one i see everywhere. I suppose it's not sorted or concurrent-safe?
      - NoodleIncident 7y ago
        I mean that people make their own per-file or per-package set implementation for their service. There's no point putting it in a common utility package even within the same company, because it's specific to the type of what they're storing. `map[T]struct{}` is only a type, it's not an implementation. You still need a handful of methods, that might be named inconsistently in each implementation by different developers. I will be happy when I never have to think about this again
      - masklinn 7y ago
        > I'm slightly surprised you found three different set implementations - `map[T]struct{}` is the idiomatic one i see everywhere. Set storage is not really the concern here, it's the set-theoretic operations which make sets useful (generally speaking, there are cases where all you need is the set being a set e.g. deduplication). So I wouldn't be surprised that GP found several different implementations of union, intersection, difference, symmetric difference, subset, superset, …
crimsonalucard 7y ago
Yeah but you can't implement it generically. That means for every conceivable input type and output type combination you have to have a new MAP or REDUCE function to handle it. All Modern languages except golang and elm only require one implementation of MAP that can handle all type combinations. It's called parametric polymorphism.
- ori_b 7y ago
  Yes, I know what it's called. I have implemented generics in compilers. I still don't miss them in most go code, in practice.
- vbezhenar 7y ago
  Java is one example of modern language without proper generics. They have syntax sugar for Object references, but you can do almost the same with golang using interface{}.
  - excursionist 7y ago
    I'm not sure what you mean by 'proper generics', but Java does have compile-time generics, ie List<T>, <A, B> B foo(A bar), etc.
    - vbezhenar 7y ago
      Proper generics would allow you to parameterize with all types including primitive ones, not just Objects. Check out java.util.Arrays class as an example of why Java's generics are not proper: https://docs.oracle.com/javase/7/docs/api/java/util/Arrays.html https://docs.oracle.com/javase/7/docs/api/java/util/Arrays.h...
      - leshow 7y ago
        You've got a kind of made up definition of 'proper'. Java has generics, they don't have the best implementation of it I've seen, but I wouldn't call it 'improper'. It's just not a word that has any specific meaning in this context. I seem to remember an article being written a while ago that found Java's type system, with the addition of generics, was unsound. Maybe that's what you're trying to say.