Sadly, it ends up far more verbose than Java when you have (as I did after tryin...

eadmund · on Aug 19, 2017

Surely you could have used interfaces for this case, no?

kuschku · on Aug 19, 2017

And how do I get the same type out that I put in? I'd end up with Java 1 style programming, no generics, and having to cast atuff from Object/interface{} everywhere.

interface{} is like Object, if it even exists once in your code, it's broken.

eadmund · on Aug 20, 2017

> And how do I get the same type out that I put in?

You can only get out the same type you put in. Presumably in your code you know that collection of Foo objects contains Foos, so you can just do:

    if foo, ok = collection.get().(Foo); !ok {
      return errors.New("expected a Foo")
    }

Write a few wrapper functions and you're done.

kuschku · on Aug 20, 2017

So, we’re back in Java 1.0, and using Object and just casting back again?

Seriously, this is why generics exist. I want to write it once, use it everywhere again, and want to have the compiler know if I made a mistake.

wyager · on Aug 19, 2017

A couple reasons that wouldn't work well (there may be more, I haven't thought about this much):

1. Using an interface would nuke your performance. Data structures where every data structure operation requires one or more vtable lookups on items in the structure can really hurt your time and space performance. To get good performance, you need true type-level generics so the compiler can specialize at compile time.

2. Anyone could put anything that followed the interface in the data structure, even if it was of the wrong type. To get any form of static type safety, you'd still have to define a wrapper type and a bunch of functions for every type you'd want to put in the data structure. You could save a bit of work by re-using your (slow) code you wrote generically using interfaces.