Source code for "Casual F# - Pattern Matching"

PatternMatching.fs

namespace CasualFSharp

module PatternMatching =

    let describeInt i =
        match i with
        | 1 -> "One"
        | 2 -> "Two"
        | _ -> "Many"

    let tryFirst (items : string list) =
        match items with
        | [] -> None
        | f :: _ -> Some f

    let firstOrDefault dflt (items : string list) =
        match tryFirst items with
        | Some x -> x
        | None -> dflt

    let printFirstFew (items : string list) =
        match items with
        | [] -> printfn "Empty list"
        | [a] -> printfn "One element: %s" a
        | [a; b] -> printfn "Two elements: %s %s" a b
        | a :: b :: _ -> printfn "More than two: %s %s ..." a b

    type MayHap<'T> =
    | Summat of 'T
    | Nowt 

    let tryFirst2 (items : string list) =
        match items with
        | [] -> Nowt
        | f :: _ -> Summat f

    let firstOrDefault2 dflt (items : string list) =
        match tryFirst2 items with
        | Summat x -> x
        | Nowt -> dflt