On 03/29/2013 04:32 PM, kenji hara wrote:

2013/3/29 Timon Gehr <timon.gehr@gmx.ch <mailto:timon.gehr@gmx.ch>>

It will be parsed as:

{     // tuple braces

It contains ';', therefore the DIP says it is a function literal brace.

     {;}   // function literal braces

}

       {{if(foo()){}}} // a non-tuple matching your specification

{    // tuple braces
     {    // function literal braces

There is no ';', therefore the DIP says it is a tuple brace.

         if (foo()){}   // "if" always appears in statement scope
     }
}

I know how it _should_ be. The DIP contradicts what you say.

Allowing value swap in tuple assignment will make language complex. I
can't agree with it.

Quite obviously it is the other way round. There will be a never-ending flood of d.D.learn posts on the topic.

       - Which right-hand sides are allowed with which semantics?

Whether it is a pattern or a tuple-literal, is distinguished by their
appeared locations.

Obviously, but this statement is not related to my question.
Valid right-hand sides seem to be at least tuples and expanded tuples (sequences). Anything else?

    4 There is no way to capture the part matched by "..."

I think this should be allowed.

auto {x, r...} = tup;
// Lowered to:
// auto x = tup[0];
// auto r = tup[1..$]

`...` is very consistent token for this purpose.

Questionable.

template X(T...) {}
alias x = X!(int, long);  // T captures {int, long}

Not really. T captures {int, long}.expand.

    5 .expand (or similar) property is missing.

Use tup[]. It is already exists.

Slicing obviously shouldn't auto-expand. It's a shortcoming of the Phobos tuple introduced because static slicing cannot be overloaded.

    6 Relation to {a: 2, b: 3}-style struct literals not explained.

I am skeptical of the necessity of tuple literal with named fields.

Sure, but you'd at least have to argue in the DIP that the parser can distinguish the two, and how.

    7 Tuple unpacking for template parameters not mentioned.

    Is there a migration path for Phobos tuples planned?

    Eg. template Tuple(T...){ alias Tuple = {T}; }
         (field spec parsing left out for illustration)