Infinite loop function with break and continue

There are two options of the loop function:

• fun loop(body: suspend LoopScope<Unit>.() -> Unit): Unit

• fun <T> loopWithResult(@BuilderInference body: suspend LoopScope<T>.() -> Unit): T

loopWithResult supports a parameterized break function whose parameter is then returned.

continue and break analogues are defined inside LoopScope interface:

@RestrictsSuspension
interface LoopScope<T> {
    suspend fun breakLoop(result: T): Nothing
    suspend fun continueLoop(): Nothing
}

suspend fun LoopScope<Unit>.breakLoop(): Nothing = breakLoop(Unit)

The solution does not depend on the exceptions, so it is safe to wrap breaks and continues with runCatching and try. The solution is also not recursive, so number of iterations is not limited by the stack size.

Example

var cur = 0
loop {
    cur++
    
    if (cur == 2) continueLoop()
    if (cur == 5) breakLoop()
    println(cur)
}

Output:

1
3
4