Functions and Loops in Programming

Learning Outcomes

• Students will understand the benefits of using functions in programming.
• Students will learn to correctly apply and call a function.
• Students will be able to describe how control flows between a called and calling function.
• Students will recognize the different parts of a function.
• Students can define and declare functions.

Problem: Finding the Sum of a Range

• A program to calculate the sum of integers from 1 to 10.
• Methods for calculating the same program
  • Method 1: Performing calculations directly in the main function.
  • Method 2: Using a for loop and accumulating the sum.
• The code to calculate the sum of integers from 1 to 10, from 20 to 37 and from 35 to 49 was demonstrated.
• The code includes different range sums in separate for loops to add specific integers individually.

Performing Repetitive Tasks

• Computers excel at repetitive tasks whereas humans find them challenging.
• Loops are one way to avoid repeating code and writing multiple function code blocks.
• Some forms of repetition aren't well suited for loops, for example, using the same code in multiple locations or handling different input variables..

Examples of Functions

• srand(seed) takes an integer seed as input.
• srand sets a seed value for a random number generator.
• The output of srand is void (nothing is returned).
• isdigit(ch) returns a Boolean true/false value indicating whether a character is a digit. Its input is a character ch.

What is a Function

• A function is a named collection of programming statements.
• It takes input, processes it, and returns an output.
• In other languages and contexts, functions are often called methods or procedures.

What Happens When a Function is Used?

• The program "invokes" or "calls" a function.
• The program sends data (arguments) to the function.
• The function performs operations on the arguments.
• The function returns a value back to the program, or it is void.
• The program resumes.

Why Use Functions

• Functions improve code reusability.
• Functions reduce the overall size of the program.
• Functions can be isolated and tested separately from the main program.

Sum of a Range: Subproblems

• Identifying the sum of a range.
• The initial user prompts lead to accepting input in a specific range.
• Each range will have a different calculation.

Sum of a Range: How to Use a Function

• Functionality to find the sum of a range of integers.
• Takes as input the starting and ending points of a numerical range.
• Calculates and returns the sum.
• Its function is called findSum().

Sum of a Range: Main Function

• A main function that prompts users for input.
• The function gathers multiple iterations of input values by looping.
• Function calls findSum to calculate and receive the result.

Function Definition - Function Header

• The structure of a function, including return type, name, and parameters.

Function Definition - Return Type

• This is the type of data that the function returns.
• A return statement is required for non-void functions.

Function Definition - Function Name

• Function names are usually verbs that indicate the action of the function.
• Names should be descriptive but concise.

Function Definition - Parameter List in Parentheses

• The parameters of the function and their types are listed in parentheses.
• Parameters can be given different types following the type name.

Function Definition - Function Body

• The function body contains the code that performs the task of the function.
• It is located within parentheses.

Implementation of findSum

• The given code provides the findSum function, its components, and purpose.

SimpleFunction.cpp

• Code for a range-summing C++ function.

Function Prototype

• Before calling a function, its prototype should be declared.
• The prototype gives the compiler information about the function.

Checkpoint: Check Point

• Write a function that receives two integers and returns the maximum of them.

Maximum Function

• Returns the larger of two integer values.

Checkpoint: Display Prime Numbers

• Demonstrating a program that finds and displays the prime numbers between 2 and 1000.