TITLE: distinguishing constructors with artificial types

(Newsgroup: comp.std.c++, 11 May 2000)

|>  > I have for long argued that more calls of ambiguity and a less
|>  > fine grained overload resolution would be helpful to the
|>  > programmer.  OTOH if you are correctly using the concept of
|>  > overloading, why should it matter because all the overloads will
|>  > do the same thing, just from different starting points.  Think
|>  > about that the next time you write an overload, if the new version
|>  > is not semantically the same as the old perhaps you should not be
|>  > writing an overload.

MINIUSSI: Alain Miniussi <alainm@cup.hp.com>

|>  That's true, except that you don't choose the name of your
|>  constructors so I guess the issue is still here (even if restricted
|>  to that situation).

KANZE: kanze@gabi-soft.de

In such cases, I've found dummy types to distinguist to be quite
helpful.  Rather than:

    X::X( double ) :
    X::X( void* ) ;

(which is ambiguous for 0, I think):

    enum ANumber { number } ;
    enum APointer { pointer } ;

    X::X( ANumber , double ) ;
    X::X( APointer , void* ) ;

The first parameter is in fact a dummy, and the constructor code never
uses it, but

    X( number , 0 )
    X( pointer , 0 )

are both perfectly unambiguous, and even the most naïve reader
understands which function will be called.



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