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0 pointsjamespwilliams4y ago0 comments

You can use type parameters in functions, but not methods. Methods are functions which have a receiver, so:

    // This is a function, you can use type parameters here:
    func Foo[T any](g T) { ... }
    
    type bar struct {}

    // This is a method, you can't use type parameters here:
    func (b bar) Foo[T any](g T) { ... }

In the second case, "Foo" is a method which has a "bar" instance as a receiver.

I've edited my original post to make it a bit clearer.

0 comments

messe4y ago

Doesn't C++ have a similar restriction, in that virtual methods cannot be templates? And in Go, with its dependence on interfaces everywhere, every method is the equivalent of /comparable to a C++ virtual method.

pjmlp4y ago

Yes, and you are right, Go interfaces are similar to pure virtual base classes in C++ (to the extent of virtual dispatch being discussed).

tubby123454y ago

so does this mean there are no generic structs in generic go?

uluyol4y ago

You can do

    type X[T any] struct{}
    func (x *X[T]) Method() {}

just fine. What you can't do is

    func (x *X[T]) Method[T2 any]() {}

_y5hn4y ago

Not saying mixing OO and generics could never have any merit, but.. Isn't a method just a function having an object as first parameter. Does Go change this beyond "syntactic sugar" somehow? Been a while from coding Go, so interested to hear.

The rationale seems to me that generics be functions first (ok, procedural), and not complecting it with objects and OO too much, whatever that mix could mean..

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egeozcan4y ago

In other words, methods cannot introduce generic types.

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