quick question about C++ function

[Pingke]

bool foo (T const & x,T const & y) const{
...
}

the third const means what?

thanks in advance!

[Frederick Gotham]

Pingke posted:

bool foo (T const & x,T const & y) const{
...
}

the third const means what?

thanks in advance!

This is a member function, and it belongs within a class.

By placing "const" after a member function's name, you indicate that the
function can be invoked on a const object of the class. By default, no
member function can be invoked on a const object of a class, so you have
to explicitly enable this functionality by writing "const" after the
function signature.

class ArbitraryClass {
public:

void ConstFunc() const {}

void NonConstFunc() {}

};
int main()
{
ArbitraryClass obj1;

obj1.ConstFunc(); /* No problem */
obj1.NonConstFunc(); /* No problem */
ArbitraryClass const obj2;

obj2.ConstFunc(); /* No problem */
obj2.NonConstFunc(); /* COMPILE ERROR */
}

--

Frederick Gotham

[Frank Puck]

"Pingke" <xl*****@gmail.com> wrote in message
news:11*********************@y41g2000cwy.googlegro ups.com...

bool foo (T const & x,T const & y) const{
...
}

the third const means what?

thanks in advance!

the method does not/cannot change the object this method is being applied to

[Pingke]

Frederick Gotham wrote:

Pingke posted:

bool foo (T const & x,T const & y) const{
...
}

the third const means what?

thanks in advance!

This is a member function, and it belongs within a class.

By placing "const" after a member function's name, you indicate that the
function can be invoked on a const object of the class. By default, no
member function can be invoked on a const object of a class, so you have
to explicitly enable this functionality by writing "const" after the
function signature.

class ArbitraryClass {
public:

void ConstFunc() const {}

void NonConstFunc() {}

};
int main()
{
ArbitraryClass obj1;

obj1.ConstFunc(); /* No problem */
obj1.NonConstFunc(); /* No problem */
ArbitraryClass const obj2;

obj2.ConstFunc(); /* No problem */
obj2.NonConstFunc(); /* COMPILE ERROR */
}

--

Frederick Gotham

thank you very much, very clear