# while loop

## Function
`while` will evaluate the condition before each loop starts. The loop body is executed when the condition is true and ends when the condition is false. It is suitable for scenarios where "you are not sure how many times you want to loop, but you know the continuation condition".

## Syntax
```bt
while condition {
    statement
}

while:label condition {
    break:label
}
```

## Example
```bt
i = 0
while i < 3 {
    println i
    i += 1
}
```

## Break and Skip
`break` ends the current cycle, `continue` enters the next round of condition judgment. Labels can be used in nested loops, such as `while:outer` with `break:outer`.

## Notes
- The loop body must give the condition a chance to become false, otherwise an infinite loop will form.
- The `while` statement itself returns `empty`.