lambda-expressions-constexpr.md

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Learn more about: constexpr lambda expressions in C++	constexpr lambda expressions in C++	04/08/2019	lambda expressions [C++], constexpr	b56346cd-fbff-475f-aeaa-ed2010c6d6f7

constexpr lambda expressions in C++

Visual Studio 2017 version 15.3 and later (available in /std:c++17 mode and later): A lambda expression may be declared as constexpr or used in a constant expression when the initialization of each data member that it captures or introduces is allowed within a constant expression.

    int y = 32;
    auto answer = [y]() constexpr
    {
        int x = 10;
        return y + x;
    };

    constexpr int Increment(int n)
    {
        return [n] { return n + 1; }();
    }

A lambda is implicitly constexpr if its result satisfies the requirements of a constexpr function:

    auto answer = [](int n)
    {
        return 32 + n;
    };

    constexpr int response = answer(10);

If a lambda is implicitly or explicitly constexpr, and you convert it to a function pointer, the resulting function is also constexpr:

    auto Increment = [](int n)
    {
        return n + 1;
    };

    constexpr int(*inc)(int) = Increment;

See also

C++ Language Reference
Function Objects in the C++ Standard Library
Function Call
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