Re: How to program this in C++?

From:

Kai-Uwe Bux <jkherciueh@gmx.net>

Newsgroups:

comp.lang.c++

Date:

Thu, 08 Nov 2007 00:58:42 -0800

Message-ID:

<fguj4p$7o3$1@murdoch.acc.Virginia.EDU>

Pavel Shved wrote:

On 8 , 10:24, Kai-Uwe Bux <jkherci...@gmx.net> wrote:

a) public inheritance. That would expose the integer part of your float
to independent manipulation (essentially like making the integer data
member public, BadIdea(tm)). On top of that, you get into all sorts of
trouble with pointers to integer objects that now could point to floats,
and more importantly, your float type would match any function

integer some_function ( integer const & )

which you probably don't want.

I think matching floats in integer funtions is the thing one likely
does want. That's done not by inheritance (which won't work in the
way you expect floats to act as integers), but by specifying user-
defined typecast rather.

I am not sure that I want floats to silently match integer functions. Have a
look at the return type. For a simple function like

  integer sqr ( integer const & i ) {
    return ( i*i );
  }

the result could be rather surprising when you feed in a float. Life will
get even more surprising if you also provide a conversion constructor
interger -> float. Then, you could do:

  float a = ...
  a = sqr( a );

and what you get is not exactly what you see.

Best

Kai-Uwe Bux