Clean functional way to break out of a sequence loop

Question

I have a sequential process with an optional exit condition. One way to write the algorithms is like this

let mutable more = true
for slot = startSlot to endSlot do
    if more then
        more <- process()

The overhead of checking more for slots that are skipped due to an exit is insignificant. Still, it seems there should be a more elegant way to express this.

Answer 1

Recursion is usual here:

let rec loop slot = if slot <= endSlot && process () then loop (slot + 1)
loop startSlot

The compiler will reduce this to a simple loop (no actual recursion takes place).

Answer 2

One way of doing this would be to use Seq.takeWhile

seq{startSlot .. endSlot} 
|> Seq.takeWhile (fun _ -> process())
|> Seq.iter ignore

This will exit the loop when process() returns false