Am I missing something ??
When u say :
For any function F and some type T declared as func F(x ...T) {}
within F x will have type []T. You can call F with a slice s of type []T
as F(s...)
Why is this needed ?? What's the point of using this "crypto-syntax"
rather than just declaring the function as func F(x [ ]T) { }
On Friday, May 3, 2019 at 1:13:02 PM UTC-4, Ian Lance Taylor wrote:
>
> On Fri, May 3, 2019 at 7:57 AM Louki Sumirniy
> <[email protected] <javascript:>> wrote:
> >
> > Ellipsis makes the parameter type into a slice, but in append it makes
> the append repeat for each element, or do I misunderstand this?
> >
> > There is a syntactic distinction between them too. Parameters it is a
> prefix to the type, append it is a suffix to the name. It neatly alludes to
> the direction in which the affected variable is operated on - inside the
> function name ...type means name []type and for append, we are splitting
> the slice into a tuple (internally), at least as I understand it, and the
> parameter is the opposite, tuple to slice.
> >
> > I sometimes lament the lack of a tuple type in Go (I previously worked a
> lot with Python and PHP), but []interface{} isn't that much more difficult
> and the ellipsis syntax is quite handy for these cases - usually loading or
> otherwise modifying essentially a super simple container array.
>
> For any function F and some type T declared as
>
> func F(x ...T) {}
>
> within F x will have type []T. You can call F with a slice s of type []T
> as
>
> F(s...)
>
> That will pass the slice s to F as the final parameter. This works
> for any variadic function F.
>
> The append function is implicitly declared as
>
> func append(to []byte, add ...byte)
>
> You can call it as
>
> append(to, add...)
>
> Here F is append and T is byte.
>
> There is a special case for append with an argument of type string,
> but other than that append is just like any other variadic function.
>
> Ian
>
>
>
> > On Friday, 3 May 2019 16:44:47 UTC+2, Ian Lance Taylor wrote:
> >>
> >> On Fri, May 3, 2019 at 7:34 AM Louki Sumirniy
> >> <[email protected]> wrote:
> >> >
> >> > The ellipsis has two uses in Go, one is in variadic parameters, the
> other is in the slice append operator. It is essentially an iterator that
> takes a list and turns it into a slice (parameters) or takes a slice and
> turns it into a recursive iteration (append). Parameters with the ellipsis
> are addressed inside the function as a slice of the type after the
> ellipsis.
> >>
> >> Note that there is nothing special about append here, it's just like
> >> passing a slice to any other variadic parameter. See
> >> https://golang.org/ref/spec#Passing_arguments_to_..._parameters .
> >>
> >> Ian
> >
> > --
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