As discussed in DConf2015: Python-like keyword arguments

[ketmar via Digitalmars-d]

On Sat, 30 May 2015 21:59:53 -0400, Michel Fortin wrote:

> On 2015-05-29 12:27:02 +0000, Jacob Carlborg <doob at me.com> said:
> 
>> And here's an implementation with language support which allows named
>> arguments but not reordering the arguments [2]. Originally implemented
>> by Michel Fortin.
>> 
>> [2] https://github.com/jacob-carlborg/dmd/tree/named_parameters
> 
> I didn't know you revived that thing too. Nice.
> 
> Make sure you take note of the related comments between Walter and me
> here:
> https://github.com/michelf/dmd/
commit/673bae4982ff18a3d216bc1578f50d40f4d26d7a
> 
> At some point my plans about this changed and I wanted to implement
> named arguments differently so it'd work for template arguments too.
> But I never go to it.

my work now allows this:
  string test (string a, string b="wow", string c="heh") {
    return a~b~c;
  }

  void main () {
    enum str = test(c: "cc", a: "aa");
    assert(str == "aawowcc");
  }

and this:
  void test(A...) (A a) {
    import std.stdio;
    foreach (auto t; a) writeln(t);
  }

  void main () {
    test(x: 33.3, z: 44.4, a: 9999, 7777, d:"Yehaw");
  }

but still not this:
  string test(T) (T a, string b="wow", string c="heh") {
    import std.conv : to;
    return to!string(a)~b~c;
  }

  void main () {
    enum str = test(c: "cc", a: 42); // can't
    //enum str = test(a: 42, c: "cc"); // WORKS
    assert(str == "42wowcc");
  }

i have to add reorder checks to template resoultion code yet.

also, no support for named "!" args.

the patch is fairly simple and almost non-intrusive (one big function in 
mtype.c and processing of NamedArgExp at different visitors). .di 
generation is supported too.
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