AFAIK, there's no release to speak of. "just" a CL one can try out: - https://go-review.googlesource.com/c/go/+/187317
hth, -s ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ On Tuesday, June 2, 2020 10:24 AM, <ffm2...@web.de> wrote: > I didn't know you can already play around with early access releases of Go2 > including generics. This is awsome! I promised myself to start working with > Go once it has generics. Therefore, could someone tell me where to download > the latest version of Go2 or tell me where the branch of it resides? This is > a little off-topic, sorry. But I thought it is not worth creating a new topic > just for this lilttle question. > > Thank you. > > Am Samstag, 30. Mai 2020 11:33:37 UTC+2 schrieb Sebastien Binet: > >> hi there, >> >> I was trying out the generics proposal >> https://github.com/golang/go/issues/15292, via the "Go2 playground": >> https://ccbrown.github.io/wasm-go-playground/experimental/generics >> >> the thing I am trying to solve is, basically, a generic way to: >> - pass a function with any number of parameters and a single return value >> - "bind" that function to a slice of pointers to values (that will point to, >> e.g., values extracted from a db) >> - create a closure that returns the value from evaluating the function with >> the bound paramaters. >> >> basically, I am defining this interface: >> type Formula interface { >> Vars() []string >> Bind(ptrs []interface{}) error >> Func() interface{} >> } >> >> that people would be able (in Go-1) to implement like so: >> >> type FormF64F32ToI64 struct { >> vars []string >> arg0 *float64 >> arg1 *float32 >> fct func(x1 float64, x2 float32) int64 >> } >> >> func (f *FormF64F32ToI64) Vars() []string { return f.vars } >> func (f *FormF64F32ToI64) Bind(ptrs []interface{}) error { >> // check number of args elided. >> f.arg0 = ptrs[0].(*float64) >> f.arg1 = ptrs[1].(*float32) >> return nil >> } >> >> func (f *FormF64F32ToI64) Func() interface{} { >> return func() int64 { >> return f.fct(*f.arg0, *f.arg1) >> } >> } >> >> so some "framework/library" code can work in terms of this Formula interface >> and let clients register formulae (with a set of column names to read from >> the database) in a relatively type-safe way, and quite performant one too >> (you pay the price of the type-assert once when you retrieve the function >> closure): >> >> usr, err := db.Formula(&FormF64F32ToI64{ >> names: []string{"col1", "col42"}, >> fct: func(x1 float64, x2 float32) int64 { return int64(x1) + int64(x2) }, >> }) >> check(err) >> >> fct := usr.Func().(func () int64) >> >> err = db.IterRows(func(tx Tx)error { >> fmt.Printf("row[%d]: %d\n", tx.ID, fct()) >> }) >> check(err) >> >> implementing the Formula interface from a given func is a pretty mechanical >> job. >> right now, I am doing it with a little go/types-based command. >> >> today, I tried to do the same with the generics proposal: >> >> ===== >> package main >> >> type Formula interface { >> Names() []string >> Bind(args []interface{}) error >> Func() interface{} >> } >> >> type Form2 (type T1,T2,U) struct { >> names []string >> arg1 *T1 >> arg2 *T2 >> fct func(t1 T1, t2 T2) U >> } >> >> func (f *Form2(T1,T2,U)) Func() interface{} { >> return func() U { >> return f.fct(*f.arg1, *f.arg2) >> } >> } >> >> func (f *Form2(T1,T2,U)) Names() []string { return f.names } >> func (f *Form2(T1,T2,U)) Bind(args []interface{}) error { >> if len(args) != 2 { >> panic("invalid number of arguments") >> } >> f.arg1 = args[0].(*T1) >> f.arg2 = args[1].(*T2) >> return nil >> } >> >> var ( >> _ Formula = (*Form2(float64,float32,int64))(nil) >> ) >> >> func main() { >> arg1 := 42.0 >> arg2 := float32(42) >> args := []interface{}{&arg1, &arg2} >> >> form := &Form2(float64,float32,int64){ >> names: []string{"f64", "data"}, >> fct: func(x1 float64, x2 float32) int64 { return int64(x1) + >> int64(x2) }, >> } >> err := form.Bind(args) >> if err != nil { panic(err) } >> >> fct := form.Func().(func() int64) >> println("fct=",fct()) >> } >> ==== >> >> it's definitely an improvement: I "just" have to write the generics code for >> functions with a given arity (say, 0, 1, ... 5) w/o having to pre-generate >> all the functions I (or my users) may need for all combinations of (types x >> arity). >> >> it's not completely satisfactory, though, as: >> - it's not "as general" a solution as what one could come up with, say, >> std::function (from C++), where you "just" have to give a function pointer >> and it handles everything else for you (arity, in this case) >> - there's probably the issue of "generic type argument" collision: >> how to differentiate (in the current scheme) between 'func(x1 float64) >> (float64, int64)' and 'func(x1, x2 float64) int64'? >> (this could perhaps be addressed w/ a different way of describing my Form2 >> generic type.) >> >> perhaps there's a better way of doing this? (perhaps even w/ "just" Go1) >> >> it'd be great to just have to write: >> var f Formula = &Form(func(float64,float64)int64){ >> names: names, >> fct: func(x1,x2 float64) float32 { return float32(x1+x2) }, >> } >> and have everything instantiated and implemented correctly. >> >> thoughts? >> >> cheers, >> -s >> >> PS: here's the direct link to the Go+Generics playground of the code above: >> https://ccbrown.github.io/wasm-go-playground/experimental/generics/#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 > > -- > 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/45c4a290-9894-437c-9bdf-b39a039f419f%40googlegroups.com](https://groups.google.com/d/msgid/golang-nuts/45c4a290-9894-437c-9bdf-b39a039f419f%40googlegroups.com?utm_medium=email&utm_source=footer). -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. 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