Yeah, i got the idea. I had already researched about it and what you can do about it. <https://stackoverflow.com/questions/50730331/mapping-concrete-types> I was only repeating what i want as a dev in this community!
El viernes, 25 de enero de 2019, 12:04:38 (UTC-3), Wagner Riffel escribió: > > you can "employ" any custom type as key but the ones that doesn't > defines equality operations, see > https://golang.org/ref/spec#Comparison_operators > as Ian already pointed out, you just can't build your custom type on > top of func, map or slice to be a valid key, anything else you can. > > On Fri, Jan 25, 2019 at 12:47 PM Victor Giordano <vituc...@gmail.com > <javascript:>> wrote: > > > > Just wanna say : It would be nice to employ a custom type as a valid key > for a map!!! :D > > > > > > El jueves, 24 de enero de 2019, 0:47:32 (UTC-3), mount...@gmail.com > escribió: > >> > >> thanks lan. > >> > >> 在 2019年1月23日星期三 UTC+8下午11:26:57，Ian Lance Taylor写道： > >>> > >>> On Tue, Jan 22, 2019 at 11:47 PM <mount...@gmail.com> wrote: > >>> > > >>> > i got : > >>> > # command-line-arguments > >>> > ./key.go:6:18: invalid operation: F() == F() (func can only be > compared to nil) > >>> > >>> Yes, that is what the language spec says and it is what I said: in Go, > >>> function values are not comparable. > >>> > >>> I wrote that code as an example to help explain why function values > >>> are not comparable. > >>> > >>> Ian > >>> > >>> > 在 2019年1月23日星期三 UTC+8上午11:59:07，mount...@gmail.com写道： > >>> >> > >>> >> When i use the func, map slice as the key of map, it isn't > work! > >>> >> So I lookup source why, i find > >>> >> > >>> >> // spec: "The comparison operators == and != must be fully > defined > >>> >> // for operands of the key type; thus the key type must not > be a > >>> >> // function, map, or slice." > >>> >> // > >>> >> // Delay this check because it requires fully setup types; > >>> >> // it is safe to continue in any case (was issue 6667). > >>> >> check.later(func() { > >>> >> if !Comparable(typ.key) { > >>> >> check.errorf(e.Key.Pos(), "invalid map key type > %s", typ.key) > >>> >> } > >>> >> }) > >>> >> // Comparable reports whether values of type T are comparable. > >>> >> func Comparable(T Type) bool { > >>> >> switch t := T.Underlying().(type) { > >>> >> case *Basic: > >>> >> // assume invalid types to be comparable > >>> >> // to avoid follow-up errors > >>> >> return t.kind != UntypedNil > >>> >> case *Pointer, *Interface, *Chan: > >>> >> return true > >>> >> case *Struct: > >>> >> for _, f := range t.fields { > >>> >> if !Comparable(f.typ) { > >>> >> return false > >>> >> } > >>> >> } > >>> >> return true > >>> >> case *Array: > >>> >> return Comparable(t.elem) > >>> >> } > >>> >> return false > >>> >> } > >>> > > >>> > -- > >>> > 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...@googlegroups.com. > >>> > For more options, visit https://groups.google.com/d/optout. > > > > -- > > 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...@googlegroups.com <javascript:>. > > For more options, visit https://groups.google.com/d/optout. > -- 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. For more options, visit https://groups.google.com/d/optout.
