Combine predicates with logical conjunction

This example wraps a lambda in a function to create a custom conjunction for use with an algorithm predicate.

How to do it…

The copy_if() algorithm requires a predicate that takes one parameter. In this recipe, we will create a predicate lambda from three other lambdas:

• First, we'll write the combine() function. This function returns a lambda for use with the copy_if() algorithm:

  template <typename F, typename A, typename B>
  auto combine(F binary_func, A a, B b) {
      return [=](auto param) {
          return binary_func(a(param), b(param));
      };
  }

The combine() function takes three function parameters – a binary conjunction and two predicates – and returns a lambda that calls the conjunction with the two predicates.

• In the main() function, we create the lambdas for use with combine():

  int main() {
   ...