Slice Index - Multiple Return

[Michael Whatcott]

Has anyone ever proposed a language change for slice access to have the option of double-return values, somewhat like map access?

Something like this?

a := []string{"1", "2"}
b, ok := a[0]
fmt.Println(b, ok) // output: "1", true
c, ok := a[4]
fmt.Println(c, ok) // output: "", false

https://play.golang.org/p/LsJq201hlv8

[Brad Fitzpatrick]

I don't recall seeing such a proposal before.

Want to file it?

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[Michael Whatcott]

Yes, I think I would like to file such a proposal. Thanks for the quick reply and encouragement!

[Jan Mercl]

On Sat, Jun 19, 2021 at 5:38 PM Michael Whatcott <mdwha...@gmail.com> wrote:

> Yes, I think I would like to file such a proposal. Thanks for the quick reply and encouragement!

I don't have a Github account, so let me please downvote this proposal here.

[Michael Whatcott]

Tell me more, Jan.

[Ian Lance Taylor]

On Sat, Jun 19, 2021 at 8:13 AM Michael Whatcott <mdwha...@gmail.com> wrote:
>

The argument against this is that it's possible to write the
two-result function yourself in ordinary Go, doubly so with the
current generics proposal.

func Index[T any](s []T, i int) (v T, ok bool) {
if i < 0 || i >= len(s) {
return
}
return s[i], true
}

It is not possible to write the existing comma-ok forms in the
language without further additions.

Ian

[Rob Pike]

This has come up before, although perhaps not as a formal proposal. It doesn't seem worth the weight.

-rob

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