what does the const mean??

[gouki]

class X {
// members
public:
int foo() const;

}


int X::foo() const // what is the const for???
{

//do something
}

 

[Peter van Merkerk]

class X {
// members
public:
int foo() const;

}


int X::foo() const // what is the const for???
{

//do something
}

It states that the X::foo() function does not modify the "observable"
state of the object. In other words from the callers perspective it
doesn't matter whether someone has called the X::foo() in past or not.
A 'getter' function is a typical example of a const function.

When a member function is declared const, that function cannot change
member variables or call other non-const functions on itself or its
members. An excepion to this rule are 'mutable' members, which may be
modified by a const function. Mutable members are typically used for
caching purposes.

 

[tom_usenet]

It states that the X::foo() function does not modify the "observable"
state of the object. In other words from the callers perspective it
doesn't matter whether someone has called the X::foo() in past or not.
A 'getter' function is a typical example of a const function.

When a member function is declared const, that function cannot change
member variables or call other non-const functions on itself or its
members.

And, importantly, const members can be called on const objects or
through const pointers and references. e.g.

const X& x = ...;
//x.nonconst(); //error
x.constmem(); //fine

Tom

 

[marbac]

class X {
// members
public:
int foo() const;

}


int X::foo() const // what is the const for???
{

//do something
}

I found this:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccelng/htm/tions_25.asp

regards marbac

 

[David Harmon]

On 29 Jul 2004 00:46:10 -0700 in comp.lang.c++, "gouki"

int X::foo() const // what is the const for???

This issue is covered in Marshall Cline's C++ FAQ. See the topic
"[18.10] What is a "const member function"?" It is always good to
check the FAQ before posting. You can get the FAQ at:
http://www.parashift.com/c++-faq-lite/

 

[Refuse to State]

Lot's of discussion about implications of the const qualifier on a
method declaration. What it means to the compiler is that the "this"
pointer inside foo is const X*, instead of X*. References to member
functions or data of class X (or it's parent classes) are implicitly
references to this->member.

dag