How to solve this problem regarding the const qualifier?

[xz]

I have a function foo as follows

void Foo::foo(const Vertex & a, const Vertex & b, const Vertex & c) {

Coordinate head;
a.calcSomething(......);
}

an got the following error information when compiling:

Foo.cpp:156: error: passing 'const Vertex' as 'this' argument of
'const void Vertex::calcSomething(......)' discards qualifiers


How to solve this problem? Isn't it enough to put calcSomething in the
following way?

class Vertex{
const void calcSomething(...){
....
};
};

 

[Ian Collins]

I have a function foo as follows

void Foo::foo(const Vertex & a, const Vertex & b, const Vertex & c) {

Coordinate head;
a.calcSomething(......);
}

an got the following error information when compiling:

Foo.cpp:156: error: passing 'const Vertex' as 'this' argument of
'const void Vertex::calcSomething(......)' discards qualifiers


How to solve this problem? Isn't it enough to put calcSomething in the
following way?

class Vertex{
const void calcSomething(...){

No, the const is qualifying the return type. To make the function
const, write

void calcSomething() const;

 

[DDD]

I have a function foo as follows

void Foo::foo(const Vertex & a, const Vertex & b, const Vertex & c) {

        Coordinate head;
        a.calcSomething(......);

}

an got the following error information when compiling:

Foo.cpp:156: error: passing 'const Vertex' as 'this' argument of
'const void Vertex::calcSomething(......)' discards qualifiers

How to solve this problem? Isn't it enough to put calcSomething in the
following way?

class Vertex{
const void calcSomething(...){
...



};
};- Hide quoted text -

- Show quoted text -

But what're the parameters of calcSomething()?

 

[Martin York]

But what're the parameters of calcSomething()?

What?

The object 'a' is a constant. Therefore you can not call methods that
modify the object. The compiler enforces this by only allowing you to
call const methods on a const object.

 

[Andy Champ]

But what're the parameters of calcSomething()?

"this" is an implicit parameter to a call of any non-static method. if
"this" is const at the time, you have to mark the method "const" to show
that you aren't going to change it.

Andy