Advanced Placement (AP) Computer Science

What is the purpose of composition of functions in programming?

1. To simplify complex data types

2. To combine simple functions into more complicated ones

3. To eliminate the need for variables

4. To replace conditional statements

The correct answer is: To combine simple functions into more complicated ones

The correct answer highlights the role of function composition as a method of combining multiple simple functions to create more complex functionality. In programming, function composition allows developers to take smaller, reusable functions and chain them together to build a new function that performs a more intricate operation. Function composition promotes code modularity and reusability, meaning that instead of having one large function that does everything, you can maintain smaller, simpler functions that can be easily tested and reused. For instance, if you have a function that converts units and another that performs calculations, you can compose them to create a new function that first converts inputs and then calculates results. This concept is widely used in functional programming and can lead to cleaner, more manageable code since it encourages breaking down tasks into discrete steps. It also aligns with the mathematical notion of function composition, where the output of one function becomes the input of another. In contrast, while simplifying complex data types, eliminating the need for variables, and replacing conditional statements can be part of programming, they do not specifically encapsulate the purpose of function composition. Each of these processes serves a different purpose in programming but does not convey the central idea of creating more complex functions by combining simple ones.