While Loop

The while statement repeatedly executes a block of code as long as its condition evaluates to true.

Syntax

while (condition) {
    // code
}

The condition is evaluated before each iteration of the loop.

If the condition evaluates to true, the loop body is executed. After the body finishes, the condition is evaluated again.

When the condition evaluates to false, the loop terminates and execution continues with the statement following the loop.

let mut i = 0

while (i < 5) {
    println(i)
    i = i + 1
}

Output:

The loop executes while i < 5. Once i becomes 5, the condition becomes false and the loop terminates.

A while loop can run indefinitely if its condition never becomes false.

while (true) {
    print("Running...")
}

A while loop can contain another while loop.

let mut i = 0

while (i < 3) {
    let mut j = 0

    while (j < 3) {
        println(i, j)
        j = j + 1
    }

    i = i + 1
}

Variables declared inside the loop body are scoped to that block.

while (true) {
    let x = 10
    println(x)
}

// x is not available here

Variables declared outside the loop can be accessed from within the loop, subject to Vesper’s variable and mutability rules.

let mut counter = 0

while (counter < 10) {
    counter = counter + 1
}

println(counter)

Output:

let mut i = 0

while (i < 10) {
    println(i)
    i = i + 1
}

The basic syntax of a Vesper while loop is:

while (condition) {
    // code
}

A while loop: