In article <3ikf08$2pf@pheidippides.axion.bt.co.uk>, John Reah <reahj@mlb371.btlabsmh.bt.co.uk> writes:
[..]
|> The pass-by-value approach is slightly more efficient in an
|> environment where integers are smaller than pointers. You
|> can also manipulate the by-value argument as a local variable
|> in the called function if you don't declare it const (I can't
|> see the benefit in declaring a by-val integer as const).

Constness of value-parameters is a matter of implementation
(e.g. you can't overload on it). For some implementations it might
be important to not accidentially modify a parameter, as its
original value is still needed.

|> Whether these issues are important from a style/consistency point
|> of view is of course up to you.
|>

Ulf Schuenemann

--------------------------------------------------------------------
Ulf Sch   nemann
Institut f   r Informatik, Technische Universit   t M   nchen.
email: schuenem@informatik.tu-muenchen.de

P Billington (paulfwb@festival.ed.ac.uk) wrote:
:  Can anyone tell me weather there are any particular benefits
: in using const referecnce over copy const parameters for simple types.

if the object is big, it doesn't need to be copied.

void P( const someBigThing& x ) as opposed to void P( someBigThing x );
which would require copying it.

Ken Walter

Hello,
 Can anyone tell me weather there are any particular benefits
in using const referecnce over copy const parameters for simple types.

eg. x(const int &val) or x(const int val)

My thoughts, at the present time, are that the former leads to more
consistent code and the latter is an obselete C form maybe loved by C
programmers but with no future.

I would be most interested to know anyones ideas or
references to texts on this subject.

Many Thanks,
 Paul

--
******************************************************************************
*                Department of Computer Science
* From: Paul Billington  E-Mail paulfwb@festival.ed.ac.uk
*

>>>>> P Billington <paulfwb@festival.ed.ac.uk> writes:

>  Can anyone tell me weather there are any particular benefits
> in using const referecnce over copy const parameters for simple types.

None.  Using pass-by-value will tend to get better performance for types
that fit nicely in a register, as the compiler doesn't have to worry about
aliasing.

Jason

>  Can anyone tell me weather there are any particular benefits
> in using const referecnce over copy const parameters for simple types.
>
> eg. x(const int &val) or x(const int val)
>
> My thoughts, at the present time, are that the former leads to more
> consistent code and the latter is an obselete C form maybe loved by C
> programmers but with no future.

The pass-by-value approach is slightly more efficient in an
environment where integers are smaller than pointers. You
can also manipulate the by-value argument as a local variable
in the called function if you don't declare it const (I can't
see the benefit in declaring a by-val integer as const).
Whether these issues are important from a style/consistency point
of view is of course up to you.