Loops: while...do Expression (F#)
The while...do expression is used to perform iterative execution (looping) while a specified test condition is true.
The test-expression is evaluated; if it is true, the body-expression is executed and the test expression is evaluated again. The body-expression must have type unit. If the test expression is false, the iteration ends.
The following example illustrates the use of the while...do expression.
open System let lookForValue value maxValue = let mutable continueLooping = true let randomNumberGenerator = new Random() while continueLooping do // Generate a random number between 1 and maxValue. let rand = randomNumberGenerator.Next(maxValue) printf "%d " rand if rand = value then printfn "\nFound a %d!" value continueLooping <- false lookForValue 10 20
The output of the previous code is a stream of random numbers between 1 and 20, the last of which is 10.
13 19 8 18 16 2 10 Found a 10!