On Sun, Jan 8, 2023 at 1:17 PM Daniel Theophanes <kardia...@gmail.com> wrote: > > When playing around with generics, I ran into what I perceive as an odd > limitation. > > I forked an audio package "beep" to do some fun generics with it. > https://github.com/kardianos/beep/blob/master/interface.go > > I was trying to use the following interfaces: > > type Point[S Size] interface { > // NOTE: Uncommenting the next line will result in errors. > // [1]S | [2]S > [2]S > } > > type Size interface { > float64 | float32 > } > > I was thinking I could change the internal data structure from float64 or > float32. This part works. I was thinking I could change the internal data > structure from one channel to two with [1]S | [2]S. Now I realize this > probably isn't a great idea to begin with, but hear me out... > > When I try to change to a union between len 1 array to len 2 array: > 1. I cannot compile any access to point[1] even if behind a len(point) guard. > 2. "for range point" appears to stop working at all, though I feel like it > should still work, as it would work on either data type. > > I fully get why this is probably not a good serious approach, but more then > anything, could someone help me with the why of the compiler errors? The > specific error is "(P has no core type)".
Well, that error is why. In the current spec and implementation, certain operations are only available if the type parameter has a "core type". See https://go.dev/ref/spec#Core_types . I believe that over time we can move toward a more flexible spec and implementation that doesn't rely on that concept, but doing that will require defining the notion of a dependent type--a type that depends on a type parameter. Ian -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/CAOyqgcVoz-8hSan4gJ-59zuXYwH465O21gPu0jBg680Ftufzzg%40mail.gmail.com.
