Chapter 4

1. What is functional composition?

Functional composition is an operation on functions. It takes two functions, f and g, and creates a third function, C, with the following property for any argument: x, C(x) = f(g(x)).

2. Functional composition has a property that is usually associated with mathematical operations. What is it?

Functional composition is not commutative. For example, squaring the increment of a number is not the same as incrementing the square of a number.

3. How can you turn an add function with two parameters into two functions with one parameter?

Consider the following function:

auto add = [](const int first, const int second){ return first + second; };

We can turn the preceding function into the following:

auto add = [](const int first){ 
    return [first](const int second){
        return first + second;
    };
};

4. How can you write a C++ function that...