Re: [boost] Re: in/out parameters, codingstylesandmaintenance

From: Noel Yap (Noel.Yap_at_[hidden])
Date: 2003-05-04 06:34:03

Rene Rivera wrote:
> 
> [2003-05-04] Noel Yap wrote:
> 
> >Rene Rivera wrote:
> >> But I know of at least one need for "out" parameters:
> >>
> >>     An asynchronous call that needs to "return" results. But because it's
> >> asynch it can't return it as the result of the call.
> >
> >Good point.  OTOH, can't this be considered an in/out parameter since
> >the caller must own the object being set?
> 
> Yes, but that's the same as saying that you can consider an in parameter an
> in/out parameter, for the same reason ;-)

You're right.  The difference is that the in parameter is const and can
therefore be differentiated from the in/out parameter at the call site.

> The called function has no interest in the previous value of the out
> parameter, if any. And that's what makes it an out parameter, not the
> ownership.

This may be true if you want to be pedantic; I'm not sure since I'm not
a linguist.

The issue of this thread is to be able to tell apart in parameters from
out parameters from in/out parameters for the purpose of being able to
tell from the call site which functions may be changing a variable.  I
think treating out parameters in your example as in/out parameters
accomplishes this.  Don't you think so?

Noel