Rust for C++ Programmers Part 7: Data Types

Re:Rust for C++ Programmers Part 7: Data Types by kzrdude on Saturday May 24, 2014 @07:14AM (#7793101)

What they mean is that there would be special cases for let patterns so that

     let (a, b) = Foo(a,b);

is a fine destructuring. It would be a special case for let, since the pattern would have to be more explicit in function arguments and in match, but I think they have a good point.

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Re:Rust for C++ Programmers Part 7: Data Types by kibwen on Saturday May 24, 2014 @01:13PM (#7793800)

I should emphasize that tuple structs are a somewhat obscure feature. Their main use case is to support newtyping:

  struct Meters(f64);
  struct Miles(f64);
  let meters = Meters(10.4);
  let miles = metric_to_imperial(meters);
  let Miles(raw_miles) = miles;

The single-arity case above constitutes the vast majority of tuple struct usage. And, as you may expect, in any other context besides tuple structs a single-arity tuple is completely silly (the only reason that we have syntax for single-arity tuples at all is to make writing macros easier).

Ultimately it's just not a feature that would be pulling its weight. If you want a structure with multiple fields where destructuring is not necessary, just use a struct in the first place. Honestly, if we found a better way to support newtyping then I wouldn't be sad if we got rid of tuple structs entirely.

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