On Sun, Aug 18, 2013 at 2:15 AM, John Colvin <john.loughran.colvin@gmail.com> wrote:
On Sunday, 18 August 2013 at 08:46:17 UTC, Timothee Cour wrote:
A)
how do I get the ith field of a std.typecons.Tuple ?
ideally, it should be as simple as:

auto t=Tuple!(int,"name",double,"name2")(1);
static assert(t.fields[0] == "name");

field is the old name for expand, retained for compatibility, it's not recommended. It gives you direct access to the tuple inside the Tuple struct, but it's for getting the variable values, not their names.

I didn't mean Tuple.field (as in Tuple.expand), I really meant the name of the corresponding entry, as shown in my example. 

If you want to get the *names* you've chosen for the tuple fields, you'll have to use traits of some sort I think.

I don't see how that would work, however I've figured out how to do it:

That's a bit of a hack, but should work. Should it be included in phobos, or, better, shall we fix Tuple with some of the recommendations i gave above?
----
import std.typecons;
auto tupleField(T,size_t i)()if(isTuple!T && i<T.length){
  enum foo0=typeof(T.init.slice!(i,i+1)).stringof;
  static assert(foo0[$-2..$]==`")`);//otherwise not a tuple with fields
  enum foo=typeof(T.init.slice!(i,i+1)).stringof[0..$-2];
  size_t j=foo.length;
  while(true){
    char fj=foo[--j];
    if(fj=='"')
      return foo[j+1..$];
  }
}
unittest{
  import std.typecons;
  auto t=Tuple!(int,"foo",double,"bar")(2,3.4);
  alias T=typeof(t);
  static assert(tupleField!(T,0)=="foo");
  static assert(tupleField!(T,1)=="bar");
}
----