Tuple poilerplate code

Simen Kjærås simen.kjaras at gmail.com
Tue Sep 1 11:44:40 UTC 2020

On Tuesday, 1 September 2020 at 02:08:54 UTC, JG wrote:
> Is there anyway to remove the boilerplate code of dealing with 
> tuples:
> I find myself having to write things like this fairly often
> auto someRandomName  = f(...); //where f returns a tuple with 
> two parts
> auto firstPart = someRandomName[0];
> auto secondPart = someRandomName[1];
> Is to possible to write something so that the above is 
> essentially equivalent to:
> assignTuple!(firstPart,secondPart) = f(...);
> The closest I can produce is using a template mixin so that I 
> would have to write:
> mixin AssignTuple!(()=>f(...),"firstPart","secondPart");

When you know the types, this works:

     import std.typecons : tuple;
     import std.meta : AliasSeq;

     int firstPart;
     string secondPart;

     AliasSeq!(firstPart, secondPart) = tuple(1, "foo");

     assert(firstPart == 1);
     assert(secondPart == "foo");

I know Timon Gehr worked on a DIP for improved tuples, which I 
think would include the syntax `auto (firstPart, secondPart) = 
tuple(1, "foo");`, but I don't know what's happened to that idea 

I also feel it's worth pointing out that Paul Backus' code looks 
elegant when used outside a map as well:

tuple(1, "foo").unpack!((i, s) {
     writeln("i (", typeof(i).stringof, "): ", i,
           ", s (", typeof(s).stringof, "): ", s);

Will print:
i (int): 1, s (string): foo


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