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Creating an Operation

Part of the Fundamentals section of Coddy's Dart journey — lesson 89 of 94.

Challenge

Easy

Our calculator needs to know which operation to perform. To represent this, we'll use a string variable that can hold one of the four basic arithmetic operators: +, -, *, or /.

Update your calculator program to:

Declare a string variable named operation
Initialize it with the multiplication operator: "*"
Add a conditional statement that checks if the operation is valid (equal to '+', '-', '*', or '/')
If the operation is not valid, set it to '+' and print exactly: "Invalid operation. Using addition (+) as default."
Print "Operation: " followed by the operation value

Try it yourself

void main() {
  print("Welcome to the Simple Calculator!");
  
  // Declare and initialize number variables
  double firstNumber = 10.5;
  double secondNumber = 5.5;
  
  // Print the numbers
  print("First number: $firstNumber");
  print("Second number: $secondNumber");
  
  // Declare and validate the operation variable
}

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

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

Project lesson

Performing Calculation

Project lesson

Displaying Result

Project lesson