C++ Lambda Expression

C++11 introduces lambadas allow you to write inline, anonymous functor.

void func3(vector<int>& v){
    for_each(v.begin() v.end(), [](int){
        // do something
    })
}

Lambda functions are just syntactic sugar for anonymous functors.

Return Types

In simple cases the return type of the lambda is deduced for you,

void func4(vector<double>& v){
    transform(v.begin(), v.end(), v.begin()), [](double){
        return d < 0.000001 ? 0 : d;
    }
}

To explicitly specify a return type, using -> T

void func4(vector<double>& v){
    transform(v.begin(), v.end(), v.begin(), [](double d) -> double {
        return d < 0.001 ? 0 : d;
    })
}

Capturing variables

void func5(vector<double>& v, const double& epsilon){
    transform(v.begin(), v.end(), v.begin(), [epsilon](double d) -> double {
        return d < epsilon ? 0 : d;
    })
}

• [&epsilon] capture by reference
• [&] captures all variables used in the lambda by reference
• [=] captures all variables used in the lambda by value
• [&, epsilon] captures variables like with [&], but epsilon by value
• [=, &epsilon] captures variables like with [&], but epsilon by reference

References: https://stackoverflow.com/questions/7627098/what-is-a-lambda-expression-in-c11