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Functions with Parameters

Part of the Fundamentals section of Coddy's Dart journey. Lesson 67 of 94.

Positional parameters allow functions to accept input values that can be used inside the function body. They're called "positional" because their order matters.

Create a function with a positional parameter:

void greet(String name) {
  print('Hello, $name!');
}

void main() {
  greet('Dart');
}

After executing the above code, the output will be:

Hello, Dart!

Create a function with multiple positional parameters:

void printSum(int a, int b) {
  int sum = a + b;
  print('The sum of $a and $b is $sum');
}

void main() {
  printSum(5, 3);
}

After executing the above code, the output will be:

The sum of 5 and 3 is 8

Challenge

Beginner

In this challenge, you'll practice creating a function with positional parameters. Positional parameters are values you pass to a function in a specific order.

Complete the calculateArea function that takes two parameters: length and width. The function should calculate and return the area of a rectangle (length × width).

Expected output:

The area of the rectangle is: 50

Try it yourself

void main() {
  // These values are already defined for you
  double length = 10.0;
  double width = 5.0;
  
  // TODO: Call the calculateArea function with length and width parameters
  // and store the result in the variable 'area'
  double area = 0.0;
  
  // This will display the result
  print('The area of the rectangle is: $area');
}

// TODO: Complete this function to calculate and return the area of a rectangle
// The function should take two parameters: length and width
double calculateArea() {
  // Your code here
  
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction to Dart

What is Dart?The main Function Printing Output Code Comments

4Operators Part 2

Comparison Operators Logical AND Logical OR Logical NOT Type Test Operators Recap - Making Comparisons

7Working with Strings

String Concatenation String Interpolation Multi-line Strings String Properties Basic String Methods

10Collections - Maps Basics

What are Maps?Creating a Map Accessing Values by Key Key-Value Pairs Getting Map Size Getting Keys Getting Values Checking if a Key Exists

13Null Safety In Depth

Understanding Null Nullable Types Non-Nullable Types Null Assertion Operator Late Initialization Recap - Handling Null Safely

16Fundamentals Challenges

Challenge: List of calculation Challenge: Sum of numbers Challenge: Find product

2Variables and Basic Data Types

What are Variables?Strings Integers (int)Doubles (double)Booleans (bool)Type Inference with 'var'Final Variables Constant Variables Naming Conventions Basic Null Safety Recap - Declaring Variables

5Operators Part 3

Null-aware Operator Null-aware Access Conditional Operator

8Control Flow - Loops

The 'for' Loop The 'while' Loop The 'do-while' Loop Using 'break' in Loops Using 'continue' in Loops Recap - Repeating Code

11Functions Basics

What are Functions?Defining a Basic Function Calling a FunctionFunctions with ParametersFunctions Returning Values The 'void' Keyword Arrow Syntax Recap - Simple Functions

14Type Conversion

Converting String to int Converting String to double Converting Numbers to String Handling Conversion Errors

3Operators Part 1

Arithmetic Operators Integer Division Modulo Operator Increment and Decrement Assignment Shortcuts Recap - Simple Calculations

6Control Flow - Decision Making

The 'if' Statement The 'else' Statement The 'else if' Statement Recap - Simple Decisions Nested 'if' Statements The 'switch' Statement

9Collections - Lists Basics

What are Lists?Creating a List Accessing by Index Getting List Length Adding Elements Removing Elements Checking if a List is Empty Iterating Over a List

12Functions Advanced

Optional Positional Parameters Named Parameters Required Named Parameters Default Parameter Values Recap - Function Parameters

15Project: Simple Calculator

Setting Up Declaring Number

Project lesson

Creating an Operation

Project lesson

Performing Calculation

Project lesson

Displaying Result

Project lesson

Practice on your own: Online Dart compiler