c++ - What does const mean following a function/method signature?

Question

(This question already has answers here): question from:https://stackoverflow.com/questions/1549869/what-does-const-mean-following-a-function-method-signature

Answer 1

It means that the method do not modify member variables (except for the members declared as mutable), so it can be called on constant instances of the class.

class A
{
public:
    int foo() { return 42; }
    int bar() const { return 42; }
};

void test(const A& a)
{
    // Will fail
    a.foo();

    // Will work
    a.bar();
}