Successful software development is all about code reuse. This is neatly summarized by the “don’t repeat yourself” (DRY) principle. Code reuse is great not just because it involves less typing, but also because it reduces the opportunity for errors. This in turn makes debugging easier. When you’re performing the same sequence of operations multiple times, it is best to encapsulate this code into a function.
In the majority of modern high-level languages, the function is the most basic
form of code reuse. Functions are ubiquitous throughout programming
languages, though some languages have more primitive forms of code reuse, too, such as
macros, jumps, and blocks. Functions in code are based on the mathematical notion of
functions. A function (e.g.,
f(x)) is a name or reference to a sequence of possibly
parameterized operations. Just like mathematical functions play an
essential role in pen-and-paper physics, functions as a programming construct
are crucial to computational physics.
Once a function is defined, it may be called as many times as desired. Calling a function will execute all of the code inside of that function. What actions are performed by the function depends on its definition and on what values are passed into the function as its arguments. Functions may or may not return values as their last operation. The logic that makes up a function may be simple or complex and is entirely at the discretion of the programmer. As a concrete ...