F# Match Many Regex

Question

I have a string that I know will match one (and only one) of three regexes. I want to try each regex in turn until a match is found. For two of the regexes it is sufficient to know that there is a match. The third regex has a capture group and returns an integer. I have an active pattern for regex:

let (|Regex|_|) pattern input =
    let m = Regex.Match(input, pattern)
    if m.Success then Some(List.tail [ for g in m.Groups -> g.Value ])
    else None

I’m new to F# and struggling for an idiomatic way to do this. I don’t really want to make a convoluted if-then-else expression, Any help would be really appreciated.

Thanks

Answer 1

With your handy function all you need to do is use match with your 3 patterns:

let regex1 = "^[1234]+$"
let regex2 = "^[abcd]+$"
let regex3 = "^ab([123])$"

let testText v =
    match v with
    | Regex regex1   _   ->         "matched 1!"
    | Regex regex2   _   ->         "matched 2!" 
    | Regex regex3 [ d ] -> sprintf "matched 3 = %d" (int d)
    | _                  ->         "no match"

testText "231" |> printfn "%s"  // matched 1!
testText "abd" |> printfn "%s"  // matched 2!
testText "ab2" |> printfn "%s"  // matched 3 = 2
testText "ab5" |> printfn "%s"  // no match