Function with default parameters

[Philippe Sigaud]

It seems doable to have some kind of function transformer (adaptor?) for
this.

from:

int foo(int a = 0, int b = 1, double c = 0.0, bool d = false) { return 1;}

alias namedParams!foo nfoo;

nfoo("d", true); // a = 0, b = 1, c = 0.0, d = true
nfoo("d", true, "b", 100); // a=0, b=100, c=0.0, d=true
nfoo(1, 2, "d", true);  // a=1, b=2, c=0.0, d=true

That is, it expects some values, then string/values couples.
Downside: in the above example, if foo accepts a string argument in first or
second position the "d" will be passed down as an argument...

or, using AA syntax:

nfoo(1, ["d":true],["b":100]);

Would that be palatable? Because I think it's doable.

To obtain the arguments names:

int foo(int a, int b, double c = 0.0, bool d = true) { return 1;}

template Name(alias foo) if (isCallable!foo)
{
    enum string Name = S!(foo.stringof);
}

template S(string s) // this template is just a trick because foo.stringof
directly displeases DMD
{
    enum string S = s;
}

writeln(Name!foo); // "int(int a, int b, double c = 0, bool d = true)"

So this gives me:

- the arguments names
- which ones have default values
- what is that default value

The difficulty here is correctly parsing the ( ,,,) part, without getting
desoriented by argument types that themselves use (,), like templated types.


Philippe
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