NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part1/415

Text File | 1996-08-05 | 1.5 KB | 49 lines

Newsgroups: comp.lang.c++
Path: artemis.sto.fdata.se!news
From: Niklas Mellin <[e-mail]>
Subject: Re: beginner question - typecasting
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Date: Thu, 4 Jan 1996 12:57:59 GMT
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Damon Bowman wrote:
>
> When you are typecasting, is there any difference between:
>
> a = int(x)
> and
> a = (int) x

[...]

Yes the first is not type casting, but a "type conversion".

When x is a  variables of built in types there is no
difference. But if x is a varible of some class for instance
the first form generates a call to that class' operator int(),
generating a compile time error message if there is no such
member function.

The 2nd form is an inheritance from plain C, and doesn't work
when x is of class type. It is also
not "safe", meaning that the compiler will not generate error
messages in certain situations, and you will get buggy code
or run time errors instead.

In general u should choose the conversion form if possible,
but sometimes a type cast can be handy. One case is if you
are using a 3rd part class library that is not well written
(read MFC) and they forgot to declare function parameters as
const and you have a const object you would like to pass to
that function. Then you can type cast your object or variable
to non const.

---
Niklas Mellin