Why use functions?

Functions are among the most important concepts and constructs of any language, so let me give you a few reasons why we need them:

• They reduce code duplication in a program. By having a specific task taken care of by a nice block of packaged code that we can import and call whenever we want, we don't need to duplicate its implementation.
• They help in splitting a complex task or procedure into smaller blocks, each of which becomes a function.
• They hide the implementation details from their users.
• They improve traceability.
• They improve readability.

Let's look at a few examples to get a better understanding of each point.

Reducing code duplication

Imagine that you are writing a piece of scientific software, and you need to calculate primes up to a limit, as we did in the previous chapter. You have a nice algorithm to calculate them, so you copy and paste it to wherever you need. One day, though, your friend, B. Riemann, gives you a better algorithm to calculate primes, which will...