[boost] Re: boost digest

From: James Curran/MVP (JamesCurran_at_[hidden])
Date: 1999-08-21 03:54:27

From: Reid Sweatman <reids_at_[hidden]>

>class foo
>{
>public:
>	foo(value_type& T = nValue,bool initialise = false)
>{ if(initialize) Initialize(T); }
>};

Am I missing something? I don't see that working as expected...
Consider the simplified:

class foo
{
        int	n;
public:
        foo(int N = 5,bool initialise = false)
{ if(initialize) n = N; }
};

Now, Case #1
Written:	Foo	X;
Effective:	foo	X(5,false);
Effect:	X.n is not initialized.

Case #2
Written:	foo	X(7)
Effective:	foo	X(7, false);
Effect:	X.n is not initialized.

Case #3
Written:	foo	X(7, true);
Effective:	same
Effect:	X.n is initialized to 7.

Case #4
Written:	foo	X(, true);
Effective:	foo	X(5, true);  // almost....
Effect:	X.n would be initialized to 5, if it weren't a syntax error.

        So, it would seem, that the only place where the default for the
second-to-last parameter could be used it, is an error.  Furthermore, the
effect of case #2 is counter-intuitive.