filtermap and chooe

fsharpexpert.fs

@@ -0,0 +1,49 @@
+open System  
+open System.Windows.Forms
+
+
+type RandomTicker(approxInterval) =    
+    let timer = new Timer()    
+    let rnd = new System.Random(99)    
+    let tickEvent = new Event<int> ()
+
+    let chooseInterval() : int = 
+        approxInterval + approxInterval / 4 - rnd.Next(approxInterval / 2) 
+
+    do timer.Interval <- chooseInterval() 
+
+    do timer.Tick.Add(fun args ->  
+        let interval = chooseInterval() 
+        tickEvent.Trigger interval; 
+        timer.Interval <- interval) 
+
+    member x.RandomTick = tickEvent.Publish 
+    member x.Start() = timer.Start() 
+    member x.Stop() = timer.Stop() 
+    interface IDisposable with member x.Dispose() = timer.Dispose()
+
+let rt = new RandomTicker(1000);;
+rt.RandomTick.Add(fun nextInterval -> printfn "Tick, next = %A" nextInterval);;
+rt.Start() 
+rt.Stop()
+
+let xs = [1..10]
+xs
+|> List.filter (fun x -> x % 2 = 0)
+|> List.map (fun x -> x * 2)
+
+let filterMap f m = (List.filter f >> List.map m)
+xs 
+|> filterMap (fun x -> x % 2 = 0) (fun x -> x * 2)
+
+xs
+|> List.choose (fun x -> 
+                match x with 
+                | x when x % 2 = 0 -> Some (x * 2)
+                | _ -> None )
+
+
+xs
+|> List.choose (function  
+                | x when x % 2 = 0 -> Some (x * 2)
+                | _ -> None )

samplecode.fsx

@@ -14,7 +14,7 @@ type MyRec = {
     id : int
 }
 
-let employee1 = {name="John Doe"; id=99}
+let employee1 = {MyRec.name="John Doe"; id=99}
 let employee2 = {name="John Doe"; id=99}
 let check = employee1 = employee2
 
@@ -35,4 +35,8 @@ printfn "%A" dtAndNum
 
 module TestModule =
     let newfunc x =
-        x + "a"
+        x + "a"
+
+let f x (g : unit -> unit) : unit =
+   printf x
+