RE: [Dev-C++] In constructor parameter list x = null

ah...yes I see. Thanks very much!




>From: Per Westermark <pw...@ia...>
>To: Somanathan Kaimal <som...@wi...>
>CC: 'Daniel Glenfield' <sp...@ho...>,      
><dev...@li...>
>Subject: RE: [Dev-C++] In constructor parameter list x = null
>Date: Mon, 31 Mar 2003 19:18:25 +0200 (CEST)
>
>No, not defensive programming.
>
>It's a default parameter value, if the parameter isn't sent in when
>making the call, i.e. a function like
>
>int sum(int a = 1, b = 2, c = 3) {
>     return a+b+c;
>}
>
>may be called as:
>
>printf("%d\n",sum()); // will print 6 (1+2+3)
>printf("%d\n",sum(5)); // will print 10 (5+2+3)
>printf("%d\n",sum(5,4)); // will print 12 (5+4+3)
>printf("%d\n",sum(5,4,7)); // will print 16 (5,4,7)
>
>Observe, that it's only the rightmost n parameters that may be ignored
>when calling a function taking default parameters. The following isn't
>allowed:
>
>int foobar(void *p = NULL, const char *s);
>
>since there exists a parameter WITHOUT a default value AFTER a parameter
>WITH a default parameter.
>
>  /Per W
>
>On Mon, 31 Mar 2003, Somanathan Kaimal wrote:
>
> > Hi,
> >
> > Its assigning a default value NULL to pParent. If you call this proc 
>with a
> > valid pointer it will override this value. This is for error checking
> > (Defensive programming).
> >
> > Somanathan
> >
> > -----Original Message-----
> > From: Daniel Glenfield [mailto:sp...@ho...]
> > Sent: Monday, March 31, 2003 6:30 PM
> > To: dev...@li...
> > Subject: [Dev-C++] In constructor parameter list x = null
> >
> > Can someone explain this to me? It's in a header file for a class
> > declaration, for the only constructor of the class.
> >
> > CPenWidthsDlg(CWnd* pParent = NULL);
> >
> > It's derived from CDialog so I assume that's got something to do with 
>it. I
> > am just confused why the parameter is assigned a NULL value. If I pass 
>in a
> > pointer will it just get assigned to NULL? then what's the point? To 
>save me
> >
> > from having to assign it to NULL in the constructor body or something?
> >
> >
> >
> >
> >
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