On Thu, Sep 12, 2019 at 9:40 PM Andrey Tcherepanov
<xnow4fippy...@sneakemail.com> wrote:
>
> well, subj - why can't I "just" do a select on a slice of channels? Yes, I
> can run a bunch goroutines with of reads on an each channel, funnel it all
> into 1 notification channel, pick up on the other side... boring stuff,
> really...
>
> But why not "just"
>
> func main() {
>
> cc := make([]chan interface{}, 10)
>
> for i := 0; i < len(cc); i++ {
> cc[i] = make(chan interface{})
> }
>
> dd := make([]chan int)
>
> for i := 0; i < 1000; i++ {
> dd = append(dd, make(chan int))
> }
>
> select {
>
> // do we need a special <-[] ?
> case i, c, v, ok := <-[]cc:
> fmt.Printf("cc replied : channel index %d, channel %v, value %v,
> ok=%v", i, c, v, ok)
>
>
> // or I dunno, not introducing a new op
> case i, d, v, ok := <-dd:
> fmt.Printf("dd sent something: channel index %d, channel %v, value %v,
> ok=%v", i, d, v, ok)
> }
>
> // or shorter, but I hope you get the drift
>
> select {
> case i, c, ok := <-[]cc:
> fmt.Printf("cc replied : channel index %d, channel %v, value %v,
> ok=%v", i, c, <-c, ok)
>
>
> case i, d, ok := <-dd:
> fmt.Printf("dd sent something: channel index %d, channel %v, value %v,
> ok=%v", i, d, <-d, ok)
> }
> }
>
>
> Why? System limitations? Rarely needed?
>
> Feels like extending language to handle that would not be too much of
> violation of an existing code. Ok, lets go nuts! Mirrored "cc <- value" for
> sending to a slice of channels! -- it should pick randomly available channel
> out of the slice of channels!
You actually can do it using the reflect package:
https://golang.org/pkg/reflect/#Select (not because we necessarily
want the reflect package to support selecting on a slice of channels,
but because there is no other reasonable way to write reflect.Select).
It's not in the language proper mainly because it doesn't seem to come
up very much. I don't think there is even a proposal for it. And
while anyone is welcome to write a proposal, it will need some
justification for why it will be worth the cost of complicating the
language.
Ian
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