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.

This quiz focuses on understanding the benefits and application of functions in programming, along with the control flow between called and calling functions. It also covers methods for calculating sums using loops and demonstrates how to perform repetitive tasks efficiently. Test your knowledge on these essential programming concepts!