Functions

In mathematics, we usually deal with two values and process them. This process could be an addition, subtraction, multiplication, etc. In programming, these processes that we apply to a value or group of values are called functions.

String firstName = "Eyzi";
String lastName = "Nakagami";
String fullName = combineNames(firstName, lastName);

Like variables, functions let us create keywords that we can use when we need a particular functionality.

After processing the inputs, a function can either terminate or return a new value. In the above example, the function combineNames takes in two string inputs and returns a new string.

Assignment

To create a function, we would indicate what inputs it takes, what outputs it gives, and how it processes the inputs.

Note that different languages have different keywords to declare a function. The most common would be the type of value it returns or just the word function.

String combineNames(String first, String last) {
  return first + " " + last;
}

In this example, we are simply adding the first name given , a space, and the last name given. The return keyword is another common keyword that just means to return the value of this specific statement back to where this function is called.

Notice that the inputs are first and last which does not match the variables from the example prior. That's because most of the time, we don't care what the variable is, only the value that it holds. When the value gets passed into this function, it gets assigned to the variable that this function uses.