Auto tuple declaration

[bearophile]

Kenji hara:

> I have posted pull request.
> https://github.com/D-Programming-Language/dmd/pull/341

Thank you. If it works well then it will be a significant improvement for D.
I invite people here to try it and use it a bit, and look for possible corner cases or troubles :-)


This is an example of D2 code that uses tuples (it's a translation of OcaML code), the new syntax is able to simplify this code, making it better:
http://rosettacode.org/wiki/Color_quantization#D

-------------------

There are two more cases where the tuple unpacking syntax will be useful, that aren't supported by pull 341 (the array were supported in a precedent version of it):


void main() {
    int[] a1 = [1, 2];
    int[2] a11;
    a11 = a1; // runtime test
    (auto x, y) = a1; // runtime test
    int[2] a2 = [1, 2];
    (auto z, w) = a2; // no need to verify a2 length at runtime here
}


import std.string;
void main() {
    string s = " foo bar ";
    (auto sa, sb) = s.split();
}


import std.algorithm, std.conv, std.string;
void main() {
    string s = " 15 27";
    (int x, int y) = map!(to!int)(splitter(s));
}


See here for more info:
http://d.puremagic.com/issues/show_bug.cgi?id=6383

-----------------

This OCaML function returns the sum of two RGB colors (here represented with a 3-tuple of FP values), this is typical code:
 
let rgb_add (r1,g1,b1) (r2,g2,b2) =
  (r1 +. r2,
   g1 +. g2,
   b1 +. b2)


A possible D syntax (a better syntax is possible):


auto rgbAdd(Color(r1,g1,b1), Color(r2,g2,b2)) {
    return Color(r1 + r2, g1 + g2, b1 + b2);
}


Note that in some cases you can't use the sometuple.tupleof syntax:


bool isGreeny(Color(r, g, b)) {
    return g > 2;
}
auto r = filter!isGreeny([Color(1,2,3), Color(4,5,6)]);


See here for more info:
http://d.puremagic.com/issues/show_bug.cgi?id=6544

Bye,
bearophile