The for Loop
When you know exactly how many times you want to loop through a block of code, use the for loop together with the in keyword, instead of a while loop:
Example
for i in 1..6 {
println!("i is: {}", i);
}This prints numbers from 1 to 5.
Note
1..6 means from 1 up to (but not including) 6.
Note
Rust handles the counter variable ( i ) automatically, unlike many other programming languages. You don't need to declare or increment it manually.
Inclusive Range
If you want to include the last number, use ..= (two dots and an equals sign):
Example
for i in 1..=6 {
println!("i is: {}", i);
}This prints numbers from 1 to 6, including 6.
Break and Continue
Just like other loops, you can use break to stop the loop and continue to skip a value:
Example
for i in 1..=10 {
if i == 3 {
continue; // skip 3
}
if i == 5 {
break; // stop before printing 5
}
println!("i is: {}", i);
}This prints 1, 2, and 4. It skips 3 and stops before 5.
Rust Loops Summary
Rust has three types of loops that let you run code over and over again. Each one is used in different situations:
loop
The simplest kind of loop. It runs forever unless you stop it with break .
loop {
// do something
if condition {
break;
}
}Use loop when you don't know in advance how many times to repeat.
while
Repeats code while a condition is true . It checks the condition before each loop.
while count <= 5 {
println!("{}", count);
count += 1;
}Use while when you want to repeat code until something happens.
for
Repeats code a fixed number of times.
for i in 1..=5 {
println!("{}", i);
}Use for when you know exactly what to loop through.
Extra Keywords
You can use these in any loop:
- break - stop the loop
- continue - skip a value in the loop
Now that you know how loops work, you are ready to start working with functions and reusable code!