Why capture by value fails in lambda

Question

Hi

Refer code below:

I just want a to be captured by reference where as b by value.

Why does it fails to compile?
https://sololearn.com/compiler-playground/c32o40MJ5397/?ref=app

Answer 1

int a = 10;
int b = 20;

[&a,b](){
cout << "Hi\n";
cout << (++a) << endl;
cout << b << endl;
}();

Answer 2

Jan right, forgot to add that part.

Answer 3

Bob_Li I made a little change to your example, so a is increased....

int a = 10;
int b = 20;

[&a,b](){
cout << "Hi\n";
cout << (++a) << endl;
cout << b << endl;
}();

cout << a;

Answer 4

You can do it this way........

int a = 10;
int b = 20;

auto lam = [](int &a, int b)
{
cout << "Hi\n";
cout << ++a << endl;
cout << b << endl;
};

lam(a, b);
cout << a;

Answer 5

Nope. I don't want to create an arguments to lambda. It should be done by capture clause only

Answer 6

Okay, here is another solution......

int a = 10;
int b = 20;
int *pa = &a;
int *pb = &b;

auto lam = [pa, pb]()
{
cout << "Hi\n";
cout << ++*pa << endl;
cout << *pb << endl;

};

lam();
cout << a;