[phobos] tie for std.typecons.Tuple

[Masahiro Nakagawa]

On Mon, 10 May 2010 21:32:00 +0900, Denis <2korden at gmail.com> wrote:

> On Mon, May 10, 2010 at 2:22 PM, Masahiro Nakagawa  
> <repeatedly at gmail.com> wrote:
>> Hi,
>>
>> Currently, Phobos has Tuple but doesn't have tie.
>> So I implemented tie for std.typecons.Tuple.
>>
>> http://www.bitbucket.org/repeatedly/scrap/src/tip/tie_.d
>>
>> Original author is 9rnsr but his version is a bit messy and overkill.
>> I substantially rewrote his tie.
>> - clear syntax (tie(&n, &d) => tie(n, d))
>> - Implicit conversion
>>
>> I would like to suggest this tie is integrated into phobos.
>>
>> What do you think of this?
>>
>
> Looks great. Just 2 questions:
> 1) Does chaining works? I.e.
> tie(a, b) = tie(c, d) = tuple(1,2); // a = b = 1, b = c = 2

http://www.bitbucket.org/repeatedly/scrap/changeset/e4c270e6c30d
Done.

> 2) You could probably use __dollar for ignored elements, to prevent
> namespace pollution and symbol conflicts:
> tie(a, $) = tuple(1, 2); // a = 1

I don't understand this. Please show me example.
I tried following code with dmd 2.046 beta:
-----
import std.stdio;

struct Dollar {}
__gshared Dollar __dollar;

void main()
{
     writeln($);
}

// foo.d(8): '$' is valid only inside [] of index or slice
-----
Umm...

> This leads to another idea: Phobos should have struct Dolllar and
> global __dollar variable so that everyone don't have to redefine it,
> just import some Phobos module and use it.

I agree.