[throwaway920102]

Go Generics provides all of this. Prior to generics, you could have filter, map, reduce etc but you needed to implement them yourself once in a library/pkg and do it for each type.

After Go added generics in version 1.18, you can just import someone else's generic implementations of whatever of these functions you want and use them all throughout your code and never think about it. It's no longer a problem.

[dkarl]

The language might permit it now, but it isn't designed for it. I think if the Go designers had intended for map, filter, et al to replace most for loops, they would have designed a more concise syntax for anonymous functions. Something more along the lines of:

    colors := items.Filter(_.age > 20).Map(_.color)

Instead of

    colors := items.Filter(func(x Item){ return x.age > 20 }).Map(func(x Item){ return x.color })

which as best as I can tell is how you'd express the same thing in Go if you had a container type with Map and Filter defined.