// [snippet:Clumsy LoopBuilder] type LoopBuilder () = let while' gd body = (fun _ -> let b = gd() if b then if Option.isSome (body ()) then Some () else body () |> (fun _ -> None) else Some ()) |> Seq.initInfinite member this.While(gd,body) = while' gd body |> Seq.tryFind (fun x -> Option.isSome x) |> ignore member this.For (s, f) = s |> Seq.tryFind (fun x -> Option.isSome (f x)) |> ignore member this.Zero () = None member this.Combine (a,b) = a |> function |Some x -> Some x |_ -> b() member this.Return (x) = x member this.ReturnFrom (x) = Some x member this.Bind (m,f) = m |> function |Some x -> f x |> Some |_ -> None member this.Delay f = f member this.Run f = f () let break' = Some () let continue' = None let loop = LoopBuilder () // [/snippet] // [snippet:Example] open System printfn "%s" "----- for" let hoge = let x = ref "／(^o^)＼" loop {for i in [1..10] do if i = 5 then printfn "%s" "five" do! continue' else if i = 2 then printfn "%s" "two" do! continue' else printfn "%d" i if i = 7 then printfn "%s" "!!!" x := "＼(^o^)／" return break' printfn "%d" i printfn "%s" "!" } !x hoge |> printfn "%s" printfn "%s" "----- while" let fuga = let x = ref "／(^o^)＼" loop {let i = ref 0 while !i < 6 do i := !i + 1 if !i = 5 then printfn "%s" "five" do! continue' else if !i = 2 then printfn "%s" "two" do! continue' else printfn "%d" !i if !i = 7 then printfn "%s" "!!!" x := "＼(^o^)／" return break' printfn "%d" !i printfn "%s" "!"} !x fuga |> printfn "%s" Console.ReadLine () |> ignore // [/snippet]