patternMatching.fs

module PatternMatch
    type Type =
        |Something of string * int
        |Nothing
    type Case =
        |CaseA of a:string * b:int
        |CaseB of a:string * b:double

    let (|A|B|C|NOPE|) (input:char) =
        match input with
        |'A' -> A
        |'B' -> B
        |'C' -> C
        |_ -> NOPE

    let check() =
        let rand = System.Random()
        let item = rand.NextDouble()
        let du =
            match item with
            |under when 0.5 < under -> Nothing
            |over ->
                Something(rand.Next().ToString(), rand.Next())
        let result =
            match du with
            |Something(s, i) -> s + i.ToString()
            |Nothing -> "Nothing"

        printfn "%A" result

        let cc =
            match item with
            |under when 0.5 < under -> CaseA("", 0)
            |over -> CaseB(over.ToString(), rand.NextDouble())

        let result2 =
            match cc with
            |CaseA("", 0) -> "Nothing"
            |CaseB(a, b) -> a + " " + b.ToString()
            |_ -> "Should not happen"
        printfn "%A" result2

        let toThree = rand.Next(4)
        let myChar =
            match toThree with
            |1 -> 'A'
            |2 -> 'B'
            |3 -> 'C'
            |_ -> '-'
        let result3 =
            match myChar with
            |A -> "Got A"
            |B -> "B is here"
            |C -> "And C wins"
            |NOPE -> "Nothing"
        printfn "%s" result3