Programming: Returning a Value/Values from a Subroutine

Programming: Returning a Value/Values from a Subroutine

Overview of Returning Values from a Subroutine

  • A subroutine in programming is a sequence of program instructions that perform a specific operation, packaged as a unit that can be used repeatedly in a program.
  • Subroutines can be functions (which return a value) or procedures (which perform an action but don’t return a value).
  • When a function finishes executing, it can return a value back to the point from which it was called. This is achieved with the use of a return statement.
  • A return statement causes the program control to transfer back to the caller of the subroutine.

Using the Return Statement

  • In most programming languages, the return keyword is used to exit from the subroutine and to optionally return a value.
  • For example, in Python, the syntax would be: return expression
  • Here ‘expression’ refers to the value or set of values you want to return. If no expression is provided, None is returned.
  • The function stops executing as soon as it encounters a return statement, even if it’s not at the end of the function.

Returning Multiple Values

  • Certain programming languages like Python allow functions to return multiple values.
  • These values can be returned either as separate return statements, a tuple, a list, or a dictionary.
  • This allows complex data to be efficiently and tidily returned from a subroutine.

Importance of Returning a Value

  • The use of return value functionality allows for modular programming, making code more reusable, functionally segregated, and easier to read and maintain.
  • The returned value can be used as an input for another function, assigned to a variable, printed out, and more.
  • Subroutines with return values allow for better testing and debugging since you can easily check the returned result for correctness.

Python Example

  • In Python, a function that adds two numbers and returns the result may look like this:
def add_numbers(num1, num2):
    sum = num1 + num2
    return sum

In the example above, the function add_numbers takes two parameters (num1 and num2), calculates their sum, and then returns the sum as the result.

Remember, understanding the mechanics of returning values from a subroutine is essential for writing efficient and modular code.