const parameters

[gc]

I came across certain code with lot of declarations like:
int foo(const double bar,const int m);
I do not see any point in making a non pointer parameter a const, or
am I missing something?

[Anupam]

gu**********@yahoo.com (gc) wrote in message news:<79**************************@posting.google. com>...

I came across certain code with lot of declarations like:
int foo(const double bar,const int m);
I do not see any point in making a non pointer parameter a const, or
am I missing something?

Why not? I would say that it is definitely to the point if you can
say to the compiler that you will *not* be changing bar or m inside
the function foo. Ok, this value will not propagate to the caller,
which is why making a pointer, a constant is a good idea. However if
you are sure that your function should not manipulate these values
inside the function, its a good idea to give yourself a compile time
escape route.
For instance :

<code excerpt>
void foo(int bar[],const int noElements) {
unsigned int i;
for(i=0;i<noElements;i++) }
/* blah blah... whatever you want to do with bar[i] */
/* What would happen if you inadvertently put a noElements--
around here */
}
}

It is a good idea to make a non pointer parameter const for this
reason.
Regards,
Anupam

[Ivan Vecerina]

"gc" <gu**********@yahoo.com> wrote in message
news:79**************************@posting.google.c om...

I came across certain code with lot of declarations like:
int foo(const double bar,const int m);
I do not see any point in making a non pointer parameter a const, or
am I missing something?

In the function's implementation, it makes just as much sense
as making any other local variable 'const'.

However, the 'const' is irrelevant in the interface of a function.
And the compiler knows this: the following declaration and definition
are recognized by the compiler as referring to the same function:

// file.h
int foo(double bar,int m);

// file.cpp
int foo(const double bar,const int m);
This is the style I typically use - keep the details away from
the user's eyes (in the header), but use const whenever it can
help code maintenance...
hth - Ivan
--
http://ivan.vecerina.com

[rihad]

On 6 Nov 2003 19:15:12 -0800, gu**********@yahoo.com (gc) wrote:

I came across certain code with lot of declarations like:
int foo(const double bar,const int m);
I do not see any point in making a non pointer parameter a const, or
am I missing something?

It just means that the implementor of foo() cannot modify their copy of passed
parameters `bar' and `m' inside foo(). It means nothing to the user of foo().

[Christopher Benson-Manica]

gc <gu**********@yahoo.com> spoke thus:

I came across certain code with lot of declarations like:
int foo(const double bar,const int m);

It's a way of reducing the number of errors you produce. Parameters are
passed by value, so changing them never affects anything outside the function.
Declaring parameters const is a way of forcing yourself to remember this.

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cyberspace.org | don't, I need to know. Flames welcome.

[Ben Pfaff]

rihad <ri***@mail.ru> writes:

On 6 Nov 2003 19:15:12 -0800, gu**********@yahoo.com (gc) wrote:

int foo(const double bar,const int m);
I do not see any point in making a non pointer parameter a const, or
am I missing something?
It just means that the implementor of foo() cannot modify their copy of passed
parameters `bar' and `m' inside foo().

It doesn't even mean that, because the function's implementation is
free to omit the const qualifiers regardless of whether they are
included in this prototype.
It means nothing to the user of foo().

--
"The expression isn't unclear *at all* and only an expert could actually
have doubts about it"
--Dan Pop