#define or const

[Andy White]

What is preferable to use for constants, #defines or const identifiers. And
where is it customary to place const indentifiers in your files? thanks.

[Steven T. Hatton]

Andy White wrote:

What is preferable to use for constants, #defines or const identifiers.
And where is it customary to place const indentifiers in your files?
thanks.

constants.
--
If our hypothesis is about anything and not about some one or more
particular things, then our deductions constitute mathematics. Thus
mathematics may be defined as the subject in which we never know what we
are talking about, nor whether what we are saying is true.-Bertrand Russell

[Jaspreet]

Andy White wrote:

What is preferable to use for constants, #defines or const identifiers. And
where is it customary to place const indentifiers in your files? thanks.

I would go for constants. It would help in during debugging since the
symbol table would be generated for constants. However, if you are
using #defines then the replacement is done before compilation and no
sysmbol table gets generated. Moreover, no typechecking is performed
for them.

Soo, I would suggest for constants.

[pven]

Andy White wrote:

What is preferable to use for constants, #defines or const identifiers. And
where is it customary to place const indentifiers in your files? thanks.

C++ recommends the usage of constants and place them on the header
file.

http://www-inolab.sys.es.osaka-u.ac...._better_c.html

[Jonathan Mcdougall]

> What is preferable to use for constants, #defines or const identifiers. And

where is it customary to place const indentifiers in your files? thanks.

http://www.parashift.com/c++-faq-lit....html#faq-29.7
Jonathan

[Ali Çehreli]

"Andy White" <br***********@ msn.com> wrote in message
news:Uv******** *********@fe06. lga...

What is preferable to use for constants, #defines or const identifiers.
As others have said, constants.
And where is it customary to place const indentifiers in your files?
thanks.

A clarification to what some of the others said: don't blindly put the
constants in header files. Like any other name, put them to the innermost
scope possible. Only when a constant is used at more than one place, move it
to an outer scope as needed.

Ali

[WittyGuy]

Andy White wrote:

What is preferable to use for constants, #defines or const identifiers. And
where is it customary to place const indentifiers in your files? thanks.

Though const identifier is much better in many ways like debugging, you
can pass them by reference and more, in some scenarios where memory is
also a constraint, #define can be used, as const may take some memory
in address space.

-Wg-

[Francis Glassborow]

In article <11************ ********@g47g20 00cwa.googlegro ups.com>,
WittyGuy <wi**********@g mail.com> writes

Andy White wrote:

What is preferable to use for constants, #defines or const identifiers. And
where is it customary to place const indentifiers in your files? thanks.

Though const identifier is much better in many ways like debugging, you
can pass them by reference and more, in some scenarios where memory is
also a constraint, #define can be used, as const may take some memory
in address space.

In practice they only take memory when you do something that involves
the value having an identity such as taking its address or passing it be
reference.

An additional consideration is whether you are using C or C++ as the
semantics of const are different (in particular, const in C++ creates a
compile time constant but this is not the case in C)

--
Francis Glassborow ACCU
Author of 'You Can Do It!' see http://www.spellen.org/youcandoit
For project ideas and contributions: http://www.spellen.org/youcandoit/projects

[Chris \( Val \)]

"Francis Glassborow" <fr*****@robint on.demon.co.uk> wrote in message
news:So******** ******@robinton .demon.co.uk...

[snip]

(in particular, const in C++ creates a
| compile time constant but this is not the case in C)

True, but even that can have it's quirks:

class Array
{
private:
const int NrElems;
int MyArray[ NrElems ];
public:
Array( int n ) : NrElems( n ) {}
};

[C++ Error] ConstTest.cpp(8 ): E2313 Constant expression required

Cheers,
Chris Val

[Bob Hairgrove]

[cross-posting removed...]

On Wed, 13 Jul 2005 00:17:03 -0700, Ali Çehreli <ac******@yahoo .com>
wrote:

A clarification to what some of the others said: don't blindly put the
constants in header files. Like any other name, put them to the innermost
scope possible. Only when a constant is used at more than one place, move it
to an outer scope as needed.

For constants needed in more than one source file, declare them with
the "extern" specifier in a header file, then define their values in a
separate .cpp file.

For constants needed only in one source file, you should declare them
as "static" directly in the .cpp source file.

--
Bob Hairgrove
No**********@Ho me.com