Hi Guys,
I was going through a product's source code. They never use const
function arguments with default value.
for instance
Never noticed following type of declaration
foo ( const int param1, const bool = false) const;
instead
of this
foo ( const int param1, bool = false) const; is used widely.
I there any drawback of using default argument with const keyword?
Oct 13 '05
14  2692 
In article <y%************ ********@news1. nokia.com>,
Risto Lankinen <rl******@hotma il.com> wrote: "David White" <no@email.provi ded> wrote in message
news:43******@ news.eftel.com. .. "Aleksey Loginov" <Al************ *@gmail.com> wrote in message > it's makes difference when your const object behave not like no-const:
>
> struct test {
> void operator () () { }
> void operator () () const { /* terrible things here */ }
> };
I don't see how that relates to my post. If a function declares a
pass-by-value parameter const, you are free to pass either a const or
non-const value to it, since it's only the copy received by the function,
not the original, that is declared const.
void foo( test t )
{
t();
}
void foo( test const t )
{
t(); /* those terrible things now happen */
}
That's an invalid overload, IOWs: you can't do that.
--
Greg Comeau / Celebrating 20 years of Comeauity!
Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it?
In article <11************ *********@g43g2 000cwa.googlegr oups.com>,
mlimber <ml*****@gmail. com> wrote: general principle of const-correctness is to make everything const
that can be const.
The problem is that can and should are different :)
--
Greg Comeau / Celebrating 20 years of Comeauity!
Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it?
Greg Comeau wrote: In article <11************ **********@g43g 2000cwa.googleg roups.com>,
Aleksey Loginov <Al************ *@gmail.com> wrote:David White wrote: ma***********@g mail.com wrote:
> I was going through a product's source code. They never use const
> function arguments with default value.
> for instance
>
> Never noticed following type of declaration
>
> foo ( const int param1, const bool = false) const;
>
> instead
> of this
> foo ( const int param1, bool = false) const; is used widely.
>
> I there any drawback of using default argument with const keyword?
I don't think there's any point in making any pass-by-value parameter const,
default or not. The const only affects how the function can use the
parameter and makes no difference to the caller. Why should the public
interface declare that a function will not modify its own private copy of an
argument? IMO such consts clutter up the public interface with junk that is
really none of the caller's business.
it's makes difference when your const object behave not like no-const:
struct test {
void operator () () { }
void operator () () const { /* terrible things here */ }
};
David is talking about const applied as a top level qualified,
not a const member fucnction. I realize you might be trying
to point of the benefits of const though; I doubt David
disagrees about their benefits, just how they sh/c/ould come about.
--
I agree with mlimber point "to make everything const that can be
const".
People, who working with your code after you, may say "Thanks" for that.
"Greg Comeau" <co****@panix.c om> wrote in message
news:di******** **@panix3.panix .com... In article <y%************ ********@news1. nokia.com>,
Risto Lankinen <rl******@hotma il.com> wrote:"David White" <no@email.provi ded> wrote in message
news:43******@ news.eftel.com. .. "Aleksey Loginov" <Al************ *@gmail.com> wrote in message
> it's makes difference when your const object behave not like
no-const: >
> struct test {
> void operator () () { }
> void operator () () const { /* terrible things here */ }
> };
I don't see how that relates to my post. If a function declares a
pass-by-value parameter const, you are free to pass either a const or
non-const value to it, since it's only the copy received by the
function, not the original, that is declared const.
void foo( test t )
{
t();
}
void foo( test const t )
{
t(); /* those terrible things now happen */
}
That's an invalid overload, IOWs: you can't do that.
Illustrates the point, though, does it not?
If you indeed have hard time seeing the point, please re-read
but replace "bar" for "foo" in one of the functions.
- Risto -
In article <mO************ ********@news1. nokia.com>,
Risto Lankinen <rl******@hotma il.com> wrote: "Greg Comeau" <co****@panix.c om> wrote in message
news:di******* ***@panix3.pani x.com... In article <y%************ ********@news1. nokia.com>,
Risto Lankinen <rl******@hotma il.com> wrote: >"David White" <no@email.provi ded> wrote in message
>news:43******@ news.eftel.com. ..
>> "Aleksey Loginov" <Al************ *@gmail.com> wrote in message
>> > it's makes difference when your const object behave not likeno-const: >> >
>> > struct test {
>> > void operator () () { }
>> > void operator () () const { /* terrible things here */ }
>> > };
>>
>> I don't see how that relates to my post. If a function declares a
>> pass-by-value parameter const, you are free to pass either a const or
>> non-const value to it, since it's only the copy received by thefunction, >> not the original, that is declared const.
>
>void foo( test t )
>{
> t();
>}
>
>void foo( test const t )
>{
> t(); /* those terrible things now happen */
>}
That's an invalid overload, IOWs: you can't do that.
Illustrates the point, though, does it not?
If you indeed have hard time seeing the point, please re-read
but replace "bar" for "foo" in one of the functions.
This thread had a few "the point"s. If you think we disagree
somehow on one or more, just restate it instead of an editing session :)
--
Greg Comeau / Celebrating 20 years of Comeauity!
Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it? This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics | |
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