What is going on here?

import std.stdio, std.typecons;

struct S
{
    int x;
    Tuple!(S) foo() { return tuple(this); }
}

void main()
{
    S s;
    s.x = 8;
    writeln((s.foo()));     //output: Tuple!(S)(S(8))
    writeln((s.foo())[0]);  //output: S(0)
}

On Monday, 24 June 2013 at 01:22:12 UTC, cal wrote:
> What is going on here?
>
> import std.stdio, std.typecons;
>
> struct S
> {
>     int x;
>     Tuple!(S) foo() { return tuple(this); }
> }
>
> void main()
> {
>     S s;
>     s.x = 8;
>     writeln((s.foo()));     //output: Tuple!(S)(S(8))
>     writeln((s.foo())[0]);  //output: S(0)
> }

import std.stdio, std.typecons;

struct S
{
    int x;
    int y;
    int z;

    auto foo() { return tuple(this.tupleof); }
}

void main()
{
    S s;
    s.x = 8;
    s.y = 9;
    s.z = 10;
    writeln((s.foo()));     //output: Tuple!(int, int, int)(8, 9, 10)

    writeln(s.foo()[2]);  //output: 10
}

Is this what you expected?
I would explain what's going on but I'd be wrong.

On 06/23/2013 09:40 PM, Anthony Goins wrote:

> On Monday, 24 June 2013 at 01:22:12 UTC, cal wrote:

>>     Tuple!(S) foo() { return tuple(this); }

> import std.stdio, std.typecons;
>
> struct S
> {
>      int x;
>      int y;
>      int z;
>
>      auto foo() { return tuple(this.tupleof); }
> }
>
> void main()
> {
>      S s;
>      s.x = 8;
>      s.y = 9;
>      s.z = 10;
>      writeln((s.foo()));     //output: Tuple!(int, int, int)(8, 9, 10)
>
>      writeln(s.foo()[2]);  //output: 10
> }
>
> Is this what you expected?

I think the OP is asking about the difference from when foo() is a non-member function:

import std.stdio, std.typecons;

struct S
{
    int x;
}

Tuple!(S) foo(S s)
{
    return tuple(s);
}

void main()
{
    S s;
    s.x = 8;
    writeln((s.foo()));     //output: Tuple!(S)(S(8))
    writeln((s.foo())[0]);  //output: S(8)
}

This time the output is S(8).

I think it is a compiler bug.

Ali

On 06/23/2013 10:07 PM, Ali Çehreli wrote:

> I think it is a compiler bug.

Make that a Phobos bug. :)

The following is a reduced program that exhibits the problem. The presence or absence of the unused member function makes a difference:

import std.typecons;

struct S
{
    int x;

    // Bizarre: Comment-out this function to pass the assert in main.
    Tuple!(S) unused()
    {
        return tuple(S(7));
    }
}

void main()
{
    auto s = S(8);

    assert(tuple(s).expand[0] == S(8));
}

Ali

On Monday, 24 June 2013 at 05:31:29 UTC, Ali Çehreli wrote:
> On 06/23/2013 10:07 PM, Ali Çehreli wrote:
>
> > I think it is a compiler bug.
>
> Make that a Phobos bug. :)
>
> The following is a reduced program that exhibits the problem. The presence or absence of the unused member function makes a difference:
>
> import std.typecons;
>
> struct S
> {
>     int x;
>
>     // Bizarre: Comment-out this function to pass the assert in main.
>     Tuple!(S) unused()
>     {
>         return tuple(S(7));
>     }
> }
>
> void main()
> {
>     auto s = S(8);
>
>     assert(tuple(s).expand[0] == S(8));
> }
>
> Ali

Actually I hadn't tried with free functions, but this test captures my problem. I'll file it now. Thanks!

On 06/23/2013 11:11 PM, cal wrote:

> I'll file it now. Thanks!

Thanks for filing:

  http://d.puremagic.com/issues/show_bug.cgi?id=10458

Ali