Dart Control flow loops

Mastering Dart Control Flow and Loops: A Comprehensive Guide

Introduction:

Unlock the full potential of Dart programming by mastering control flow structures and loops. In this comprehensive guide, explore the intricacies of for, while, and do-while loops, and learn how to effectively use break and continue statements. Gain a solid understanding of these fundamental concepts, paving the way for more efficient and structured Dart programming.

Dart, a programming language developed by Google, provides various control flow structures for implementing loops. The most common types of loops in Dart are for, while, and do-while. Here’s an overview of each:

Dart For Loop:

• The for loop in Dart has a similar syntax to many other programming languages.
• It consists of an initialization statement, a condition expression, and an iteration statement.

dart

for (initialization; condition; iteration) {
// code to be executed
}

Example:

dart

for (int i = 0; i < 5; i++) {
print('Iteration $i');
}

Dart While Loop:

The while loop in dart  continues to execute a block of code as long as the specified condition is true.

dart

while (condition) {
// code to be executed
}

Example:

dart

int count = 0;
while (count < 3) {
print('Count is $count');
count++;
}

Dart Do-While Loop:

The do-while loop in Dart  is similar to the while loop, but it guarantees that the block of code is executed at least once before the condition is checked.

dart

do {
// code to be executed
} while (condition);

Example:

dart

int num = 1;
do {
print('Number is $num');
num++;
} while (num <= 3);

These are the basic loop constructs in Dart. You can use them to create iterative structures in your code, and they play a crucial role in controlling the flow of your program. Additionally, Dart provides other features like break and continue statements for more fine-grained control within loops.

Dart For Loop:complete example with explanation

Let’s walk through a complete example of a for loop in Dart, including an explanation of each part.

dart

void main() {
// Example 1: Simple for loop
print("Example 1: Simple for loop");
for (int i = 0; i < 5; i++) {
print("Iteration $i");
}

// Example 2: Looping through a list
print("\nExample 2: Looping through a list");
List<String> fruits = ["Apple", "Banana", "Orange", "Grapes"];
for (int i = 0; i < fruits.length; i++) {
print("Fruit at index $i: ${fruits[i]}");
}

// Example 3: Using a for loop to calculate a sum
print("\nExample 3: Using a for loop to calculate a sum");
int sum = 0;
for (int i = 1; i <= 5; i++) {
sum += i;
}
print("Sum of numbers from 1 to 5 is $sum");
}

Explanation:

Example 1: Simple for loop

for (int i = 0; i < 5; i++): This is the basic structure of a for loop.
int i = 0: Initialization – Setting up the loop variable i to start at 0.
i < 5: Condition – The loop will continue as long as i is less than 5.
i++: Iteration – Incrementing i by 1 after each iteration.
print(“Iteration $i”): Printing the value of i during each iteration.

Example 2: Looping through a list

List<String> fruits = [“Apple”, “Banana”, “Orange”, “Grapes”]: Declaring a list of strings.
for (int i = 0; i < fruits.length; i++): Looping through the list using its length.
print(“Fruit at index $i: ${fruits[i]}”): Printing each element of the list along with its index.

Example 3: Using a for loop to calculate a sum

int sum = 0;: Initializing a variable sum to zero.
for (int i = 1; i <= 5; i++): Looping from 1 to 5 (inclusive) to calculate the sum.
sum += i;: Accumulating the sum by adding the current value of i in each iteration.
print(“Sum of numbers from 1 to 5 is $sum”): Printing the final sum.

This example demonstrates the versatility of the for loop in Dart, showcasing its usage in simple counting, iterating through lists, and performing a cumulative calculation.

Dart While Loop:complete example with explanation

Let’s go through a complete example of a while loop in Dart, including an explanation of each part.

dart

void main() {
// Example 1: Simple while loop
print("Example 1: Simple while loop");
int count = 0;
while (count < 5) {
print("Count is $count");
count++;
}

// Example 2: Using while loop to find the power of 2
print("\nExample 2: Using while loop to find the power of 2");
int base = 2;
int exponent = 1;
int result = 1;
while (exponent <= 5) {
result *= base;
exponent++;
}
print("2 raised to the power of 5 is $result");

// Example 3: Using while loop with input
print("\nExample 3: Using while loop with input");
int Number = 0;
print("Enter a positive number (enter -1 to stop): ");
while (Number != -1) {
Number = int.parse(stdin.readLineSync()!);
print("You entered: $Number");
}
print("Loop terminated as -1 was entered.");
}

Explanation:

Example 1: Simple while loop

int count = 0;: Initializing a variable count to 0.
while (count < 5): The loop will continue as long as count is less than 5.
print(“Count is $count”): Printing the value of count during each iteration.
count++;: Incrementing count by 1 after each iteration.

Example 2: Using while loop to find the power of 2

int base = 2;, int exponent = 1;, int result = 1;: Initializing variables for the power calculation.
while (exponent <= 5): Looping until the exponent reaches 5.
result *= base;: Calculating the power of 2 in each iteration.
exponent++;: Incrementing the exponent after each iteration.
print(“2 raised to the power of 5 is $result”): Printing the final result.

Example 3: Using while loop with input

int Number = 0;: Initializing a variable for input.
print(“Enter a positive number (enter -1 to stop): “): Prompting the for input.
while (Number != -1): The loop continues until the enters -1.
Number = int.parse(stdin.readLineSync()!);: Reading input from the console.
print(“You entered: $Number”): Printing the entered number during each iteration.
The loop terminates when the enters -1.

These examples illustrate how the while loop in Dart can be used for simple counting, iterative calculations, and interactive input scenarios.

Dart Do-While Loop:complete example with explanation

Let’s walk through a complete example of a do-while loop in Dart, including an explanation of each part.

dart

import 'dart:io';

void main() {
// Example 1: Simple do-while loop
print("Example 1: Simple do-while loop");
int num = 1;
do {
print("Number is $num");
num++;
} while (num <= 3);

// Example 2: Using do-while loop for input validation
print("\nExample 2: Using do-while loop for input validation");
int Input;
do {
print("Enter a number between 1 and 10: ");
Input = int.parse(stdin.readLineSync()!);
} while (Input < 1 || Input > 10);
print("You entered a valid number: $Input");

// Example 3: Performing an action at least once
print("\nExample 3: Performing an action at least once");
String Choice;
do {
print("Do you want to continue? (yes/no): ");
Choice = stdin.readLineSync()!;
} while (Choice.toLowerCase() == 'yes');
print("You chose to stop.");

}

Explanation:

Example 1: Simple do-while loop

int num = 1;: Initializing a variable num to 1.
do { … } while (num <= 3);: The loop body will be executed at least once, and then it will continue as long as num is less than or equal to 3.
print(“Number is $num”);: Printing the value of num during each iteration.
num++;: Incrementing num by 1 after each iteration.

Example 2: Using do-while loop for input validation

int Input;: Declaring a variable to store input.
do { … } while (Input < 1 || Input > 10);: The loop continues until the enters a number between 1 and 10 (inclusive).
print(“You entered a valid number: $Input”);: Printing the valid input.

Example 3: Performing an action at least once

String Choice;: Declaring a variable to store choice.
do { … } while (Choice.toLowerCase() == ‘yes’);: The loop continues as long as the enters “yes” (case-insensitive).
print(“You chose to stop.”);: Printing a message when the decides to stop.

These examples demonstrate the use of the do-while loop in Dart, which ensures that the loop body is executed at least once before checking the loop condition. This can be useful for scenarios where you want to perform an action and then decide whether to continue based on a condition.

Dart break : complete example with explanation

The break statement in Dart is used to prematurely exit a loop.

Let’s go through a complete example of using break in a for loop:

dart

void main() {
// Example: Using break in a for loop
print("Example: Using break in a for loop");

for (int i = 0; i < 5; i++) {
print("Iteration $i");

if (i == 2) {
print("Breaking out of the loop at iteration 2");
break; // Exit the loop when i is equal to 2
}
}

print("Loop finished");
}

Explanation:

for (int i = 0; i < 5; i++): This is a simple for loop that iterates from 0 to 4.
print(“Iteration $i”): Printing the current iteration number during each loop iteration.
if (i == 2) { … }: Checking if the current iteration is equal to 2.
print(“Breaking out of the loop at iteration 2”): Printing a message when the condition is met.
break;: This statement is executed when i is equal to 2, causing the loop to exit prematurely.
print(“Loop finished”): Printing a message indicating that the loop has finished.
When you run this program, you’ll see output similar to:

Example: Using break in a for loop
Iteration 0
Iteration 1
Iteration 2
Breaking out of the loop at iteration 2
Loop finished

The break statement is particularly useful when you want to exit a loop based on a specific condition. In this example, the loop breaks when the iteration variable i is equal to 2.

The output shows that the loop finishes prematurely after encountering the break statement.

Dart continue : complete example with explanation

The continue statement in Dart is used to skip the rest of the current iteration of a loop and proceed to the next one.

Let’s go through a complete example of using continue in a for loop:

dart

void main() {
// Example: Using continue in a for loop
print("Example: Using continue in a for loop");

for (int i = 0; i < 5; i++) {
if (i == 2) {
print("Skipping iteration 2 using continue");
continue; // Skip the rest of the loop body and move to the next iteration
}

print("Iteration $i");
}

print("Loop finished");
}

Explanation:

for (int i = 0; i < 5; i++): This is a simple for loop that iterates from 0 to 4.
if (i == 2) { … }: Checking if the current iteration is equal to 2.
print(“Skipping iteration 2 using continue”): Printing a message when the condition is met.
continue;: This statement is executed when i is equal to 2, causing the loop to skip the rest of the loop body and move to the next iteration.
print(“Iteration $i”): This line is skipped for the iteration where i is equal to 2.
print(“Loop finished”): Printing a message indicating that the loop has finished.

When you run this program, you’ll see output similar to:

Example: Using continue in a for loop
Iteration 0
Iteration 1
Skipping iteration 2 using continue
Iteration 3
Iteration 4
Loop finished

As you can see, when the loop encounters the continue statement during iteration 2, it skips the print statement and moves on to the next iteration.

The output shows that iteration 2 is skipped, and the loop continues with the remaining iterations.

َQuiz about Dart control flow, loops:15 questions with explanation

let’s create a quiz based on the concepts we covered about Dart control flow, loops, for, while, do-while loops, break, and continue.

Each question will be followed by an explanation of the correct answer.

Quiz: Dart Control Flow and Loops

1-What is the purpose of the for loop in Dart?

a) To declare variables
b) To define functions
c) To create a loop that repeats a statement or a block of statements
Explanation: The correct answer is (c). The for loop is used to create a loop that repeats a statement or a block of statements a specified number of times.

2-How is the condition checked in a while loop?

a) Before the loop body is executed
b) After the loop body is executed
c) Only once at the beginning of the loop
Explanation: The correct answer is (a). In a while loop, the condition is checked before the loop body is executed.

3-In a do-while loop, when is the condition checked?

a) Before the loop body is executed
b) After the loop body is executed
c) Only once at the beginning of the loop
Explanation: The correct answer is (b). In a do-while loop, the condition is checked after the loop body is executed, ensuring that the loop body is executed at least once.

4-What does the break statement do in Dart?

a) Continues to the next iteration of the loop
b) Exits the loop prematurely
c) Skips the current iteration and moves to the next one
Explanation: The correct answer is (b). The break statement in Dart is used to prematurely exit a loop.

5-When is the continue statement used in a loop?

a) To exit the loop
b) To skip the rest of the current iteration and move to the next one
c) To restart the loop from the beginning
Explanation: The correct answer is (b). The continue statement is used to skip the rest of the current iteration and move to the next one.

6-How is the loop variable initialized in a for loop?

a) Before the loop body is executed
b) After the loop body is executed
c) Only once at the beginning of the loop
Explanation: The correct answer is (c). In a for loop, the loop variable is initialized only once at the beginning of the loop.

7-What is the purpose of the loop condition in a while loop?

a) To initialize the loop variable
b) To determine when to exit the loop
c) To calculate the sum of loop iterations
Explanation: The correct answer is (b). The loop condition in a while loop determines when to exit the loop.

8-In a do-while loop, when is the loop condition checked?

a) Before the loop body is executed
b) After the loop body is executed
c) Only once at the beginning of the loop
Explanation: The correct answer is (a). In a do-while loop, the loop condition is checked before the loop body is executed.

9-What does the following for loop do?

dart

for (int i = 0; i < 3; i++) {
print(“Iteration $i”);
}
a) Prints “Iteration 0” three times
b) Prints “Iteration 0,” “Iteration 1,” “Iteration 2”
c) Prints “Iteration 1” three times
Explanation: The correct answer is (b). The for loop iterates three times, printing “Iteration 0,” “Iteration 1,” and “Iteration 2.”

10-How is the loop variable updated in a for loop?

a) Before the loop body is executed
b) After the loop body is executed
c) During each iteration with the iteration statement
Explanation: The correct answer is (c). In a for loop, the loop variable is updated during each iteration with the iteration statement.

11-What is the output of the following code?

dart

int count = 0;
while (count < 4) {
print(“Count is $count”);
count++;
}
a) Count is 0, 1, 2, 3, 4
b) Count is 0, 1, 2, 3
c) Count is 1, 2, 3, 4
Explanation: The correct answer is (b). The while loop prints “Count is 0,” “Count is 1,” “Count is 2,” and “Count is 3.”

12-In a do-while loop, how many times is the loop body executed if the condition is initially false?

a) Zero times
b) One time
c) Infinite times
Explanation: The correct answer is (b). In a do-while loop, the loop body is executed at least once, even if the condition is initially false.

13-What does the following code do?

dart

do {
print(“This is a do-while loop”);
} while (false);
a) Prints the message once
b) Prints the message twice
c) Does not print anything
Explanation: The correct answer is (a). The do-while loop prints the message once even though the condition is false initially.

14-When is the continue statement useful?

a) To exit the loop
b) To skip the rest of the current iteration and move to the next one
c) To restart the loop from the beginning
Explanation: The correct answer is (b). The continue statement is useful for skipping the rest of the current iteration and moving to the next one.

15-What is the purpose of the loop condition in a for loop?

a) To initialize the loop variable
b) To determine when to exit the loop
c) To calculate the sum of loop iterations
Explanation: The correct answer is (b). The loop condition in a for loop determines when to exit the loop.