Definite Loop - For Loop

What Is a for Loop?

A for loop is a definite loop, meaning, the number of iterations is defined.

Syntax

The for loop is followed by a variable that iterates over a list of values. The general syntax is :

Example

The following example uses a for loop that prints 5 numbers.

  fn main() {
    //define a for loop 
    for i in 0..5 {
      println!("{}", i);
    }
}

output

  0
1
2
3
4

Explanation

  • for loop definition

    • On line 3 a for loop is defined.
      • Variable i is an iterator variable that iterates over the range with the lower bound as 0 and the upper bound as 5. From here the body of the loop starts.

  • for loop body

    • The body of the for loop is defined from line 3 to line 5
    • In each iteration:
      • On line 4, the value of the variable i is printed.
      • The value of the variable i is incremented by 1.

  • The iterator variable i traverses over the range until the upper bound is reached.

Note: The lower bound is inclusive and the upper bound is exclusive in the range

The following illustration explains this concept:

Enumerate

To count how many times the loop has already executed, use the .enumerate() function.

  • Syntax The general syntax is :

  • Example

The example below prints the frequency of iterations and the value of variable.

  fn main() {
  for (count, variable) in (7..10).enumerate() {
      println!("count = {}, variable = {}", count, variable);
  }
}

output

  count = 0, variable = 7
count = 1, variable = 8
count = 2, variable = 9

Explanation

  • enumerated for loop definition

    • On line 2 an enumerate for loop is defined.
    • The variable variable iterates over the range with the lower bound as 7 and the upper bound as 10 and a variable count which shows how many times the loop is iterated. From here the body of the loop starts.

  • enumerated for loop body

    • On line 3, the value of count and variable is printed and then incremented by 1.

Quiz

--- primaryColor: steelblue secondaryColor: '#e8e8e8' textColor: black shuffleQuestions: false shuffleAnswers: true locale: en --- # What is the output of the following code? ``` fn main() { for i in 0..5{ if i % 4 == 0 { print!("{}", i); } } } ``` - [ ] 04 - [ ] 01234 # What is the output of the following code? ``` fn main() { for (count, variable) in (7..10).enumerate() { if count * 2 == 4{ println!("count = {}, variable = {}", count, variable); } } } ``` - [ ] count = 0, variable = 7 count = 1, variable = 8 count = 2, variable = 9 - [ ] count = 2, variable = 9
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Last updated 25 Jan 2024, 05:11 +0530 . history