Lambda Functions

Inline Anonymous Functions

// Syntax: [capture](params) -> return_type { body }
auto square = [](int x) { return x * x; };
cout << square(5);   // 25

// With STL algorithms
vector<int> v = {3,1,4,1,5,9};
sort(v.begin(), v.end(), [](int a, int b) { return a > b; }); // descending

int evens = count_if(v.begin(), v.end(), [](int x){ return x%2==0; });

Capturing outer variables

int threshold = 5;

auto isAbove = [threshold](int x) { return x > threshold; }; // capture by value
auto addTo   = [&threshold](int x){ return x + threshold; }; // capture by ref
auto all     = [=](int x){ return x > threshold; };           // all by value
auto allRef  = [&](int x){ threshold++; return x; };          // all by ref

Your Task

Write applyToAll(vector<int> v, function<int(int)> fn) that applies fn to every element and returns the result vector.