Dart For Loop

Dart For Loop

Welcome to Dart For Loop tutorial.

In this tutorial, we will learn how to write a for loop and some Dart example programs to understand the usage of Dart For Loop.

Syntax of Dart For Loop

Following is the syntax of For Loop in Dart programming language.

 for (initialization; boolean_expression; update) {
     //statement(s)

 }

initialization section can contain one or more variables being initialized.

Based on the output of boolean_expression during each iteration, it is decided whether to execute the statements or not in the for loop. If boolean_expression evaluates to true, then the statements inside the for loop are executed. If boolean_expression evaluates to false, then the statements inside the for loop are not executed.

update section can contain update to the variables like increment, decrement or any kind of change in their values.

Working of For Loop

1. When the program control comes to a for loop statement, it executes the initialization block.
2. And then evaluates the boolean_expression.
   1. If boolean_expression evaluates to true,
      1. then the statements inside the for loop are executed.
      2. And then the update section is executed.
      3. Now go to step 2.
   2. If boolean_expression evaluates to false,
   3. Go out of the loop.

Dart For Loop to calculate Factorial of a number

In the following example, we will use Dart For Loop to calculate the factorial of a given number.

Dart program

void main(){
	var n = 6;
	var factorial = 1;
	
	//for loop to calculate factorial
	for(var i=2; i<=n; i++) {
		factorial = factorial*i;
	}
	
	print('Factorial of ${n} is ${factorial}');
}

Output

Factorial of 6 is 720

Dart Nested For Loop

You can write a For Loop inside another For Loop in Dart. This process is called nesting. Hence Nested For Loop.

Dart For Loop to print * triangle

In the following example, we will use Dart For Loop to *s in the shape of right angle triangle.

Dart program

import 'dart:io';

void main(){
	var n = 6;
	
	print('');
	
	for(var i=1; i<=n; i++) {
		for(var j=0; j<i; j++) {
			stdout.write(' *');
		}
		print('');
	}
}

Output

Note: Here we used stdout.write() to write to console without new line at the end, unlike print().

Conclusion

In this Dart Tutorial, we learned the syntax and how to use for loop with the help of example programs.