CODEWITHSUNDEEP
c++lambda
Edamame
Edamame

Reputation: 25366

c++: input of a lambda expression

I have the following code:

auto x_is_valid = [](const MyX &x) -> bool {
    return x.source != MyXValue::ABC;
};

auto objects = var_.var_in_box(*a, b, c, x_is_valid);

I am wondering:

How do I read this properly?

Thanks!

Upvotes: 1

Views: 110

Answers (2)

anatolyg
anatolyg

Reputation: 28278

A mathematical analogy might help. Imagine a function f(x) = x^2.

How is f computed?

It's right there: for any x, the formula for computing is f(x) = x^2.

Where does it take its input parameter?

From the caller.

The "answers" above are pretty pointless, but if you understand them in a context of a function in a mathematical sense, they might be helpful.

Upvotes: 2

R Sahu
R Sahu

Reputation: 206697

If var_.var_in_box, expects a bool as the last argument, then the call

auto objects = var_.var_in_box(*a, b, c, x_is_valid);

should result in a compile error.

If the above line compiles without any error, then the last argument type of the above is a callable object, not a bool. Presumably, the function uses the passed in callable object to make a function call. It's not possible to determine from the posted code how the callable is called in the implementation of var_in_box member function of the class.

Upvotes: 0

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