Project page for clamp - the C++ lambda preprocessor The C++ lambda preprocessor (clamp) converts C++ code containing lambda expressions into ordinary C++ code. Here's a simple example: vector<int> v; // ... std::for_each (v.begin(), v.end() , lambda (int &p) { if (p == 5) p = 0; } ); This example uses the standard algorithm for_each to apply an anonymous function to each element of a vector.