[foldr]

I don’t think it makes sense to see built in operations on arrays and maps as generic functions. If 'len' was some kind of built-in generic function then you'd expect to be able to monomorphize it like this:

    func intLen(foo []int, lenfunc func ([]int) int) int {
      return lenfunc(foo)
    }

    intLen([]int{1,2,3}, len)

There is just no sense in which Go 1.17 has “generic types” and (e.g.) C doesn’t. All statically typed languages allow you to define arrays of different types and use the same operators on these arrays. Go adds a handful of additional built in types (slices, maps, channels).

The idea that some completely ordinary language features somehow constitute a crippled version of generics that has been 'turned off' for regular users seems to be an artefact of certain communities' hobbyhorsing over Go's (former) lack of generics.

[erik_seaberg]

As a thing that takes an argument and returns a result, I would have expected len to be an ordinary function. That I don’t is only because I remember the disappointing state of the language at launch.