discrimination of constructors with same number of parameters

[spir]

On Thu, 30 Dec 2010 17:10:00 +0100
"Jérôme M. Berger" <jeberger at free.fr> wrote:

> Steven Schveighoffer wrote:
> > What I would suggest is static factory methods.  The issue with any kind
> > of typedef (be it with the soon-to-be-deprecated typedef keyword or with
> > a proxy struct), is that what does this mean?
> > 
> > auto obj = new Foo([1, 2, 3], "blah");
> > 
> > Is "blah" a filename or a message?
> > 
> --> Error, Foo (int[], string) does not exist.

Yes, you are right. Typedef-like solutions need core support by the language with a kind of hint to the compiler... playing the role of type in Jérôme's sample below.

> > Whereas, if you use factory methods:
> > 
> > auto obj = Foo.createWithFilename([1,2,3], "blah"); // "blah" is a filename
> > auto obj = Foo.createWithMessage([1,2,3], "blah"); // "blah" is a message

Factory methods are definitely convenient. The single objection is rather conceptual: it defeats the purpose of a major language feature, namely constructor; which happens to have a clear meaning from the modelling point of view.

> > The code becomes crystal clear.  Reduce verbosity as you see fit ;)
> > 
> auto obj = new Foo ([1, 2, 3], Filename ("blah"));
> auto obj = new Foo ([1, 2, 3], Message ("blah"));

Conceptually, I would prefere this -- at the use place. But if requires obfuscating the code at the definition point (with eg wrapper structs), is it worth it?

If we could write eg:
	typedef string Message;
	auto obj = new Foo ([1, 2, 3], Message ("blah"));
then I would be happy, I guess ;-)

Denis
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