Bug 10119 – Add tuple overload which automatically captures the names of symbols

Currently tuple() can capture the state of local variables and wrap them in a Tuple struct. However you won't have name access: ----- import std.typecons; auto foo() { int x, y; return tuple(x, y); } void main() { assert(foo.x == 0); // fails, no "x" } ----- As a workaround you can explicitly name the fields at the call site: ----- auto foo() { int x, y; return Tuple!(typeof(x), "x", typeof(y), "y")(x, y); } ----- But this is tedious and boring, and we can do much better than this. I propose we introduce either an overload of tuple (if it's possible) or a newly named function which automatically wraps the arguments by name into a tuple. Here's an example implementation: ----- import std.string; import std.typecons; auto tuplify(Aliases...)() { string gen() { string[] lhs; string[] rhs; foreach (idx; 0 .. Aliases.length) { lhs ~= format("typeof(Aliases[%s])", idx); lhs ~= format("__traits(identifier, Aliases[%s])", idx); rhs ~= format("Aliases[%s]", idx); } return format("Tuple!(%s)(%s)", lhs.join(", "), rhs.join(", ")); } return mixin(gen()); } auto func() { int x = 1; string y = "2"; return tuplify!(x, y); } void main() { auto res = func; assert(res.x == 1); assert(res.y == "2"); } -----

No, this instead. (per IRC request) https://gist.github.com/JakobOvrum/5608585 ------------------------------------------ import std.typecons : Tuple; import std.typetuple : TypeTuple; template NameTypePairs(alias front, vars...) { private enum name = __traits(identifier, front); private alias pair = TypeTuple!(typeof(front), name); static if(vars.length == 0) alias NameTypePairs = pair; else alias NameTypePairs = TypeTuple!(pair, NameTypePairs!vars); } auto tuplify(vars...)() { return Tuple!(NameTypePairs!vars)(vars); }

(In reply to comment #1) > No, this instead. (per IRC request) That one is also faster and more generic-style instead of magic-mixin-style. *Nods head in approval*.

I think we should just add tuples to D. I think a possible syntax is tuple(...).

@jcrapuchettes: I have a feeling this may have been something you were looking for when you mentioned named tuples yesterday? Either way it's a small piece of code you can use adapt and right now, so feel free to take it.