Merge branch 'master' of https://github.com/adambard/learnxinyminutes-docs

1 files changed, 158 insertions, 158 deletions

diff --git a/fsharp.html.markdown b/fsharp.html.markdown
index 49951c78..76318d7d 100644
--- a/fsharp.html.markdown
+++ b/fsharp.html.markdown
@@ -5,7 +5,7 @@ contributors:
 filename: learnfsharp.fs
 ---
 
-F# is a general purpose functional/OO programming language.  It's free and open source, and runs on Linux, Mac, Windows and more. 
+F# is a general purpose functional/OO programming language.  It's free and open source, and runs on Linux, Mac, Windows and more.
 
 It has a powerful type system that traps many errors at compile time, but it uses type inference so that it reads more like a dynamic language.
 
@@ -90,7 +90,7 @@ let simplePatternMatch =
     | _ -> printfn "x is something else"   // underscore matches anything
 
 // F# doesn't allow nulls by default -- you must use an Option type
-// and then pattern match.  
+// and then pattern match.
 // Some(..) and None are roughly analogous to Nullable wrappers
 let validValue = Some(99)
 let invalidValue = None
@@ -115,39 +115,39 @@ printfn "A string %s, and something generic %A" "hello" [1;2;3;4]
 // into a string, similar to String.Format in C#.
 
 // ================================================
-// More on functions 
+// More on functions
 // ================================================
 
 // F# is a true functional language -- functions are first
-// class entities and can be combined easy to make powerful
+// class entities and can be combined easily to make powerful
 // constructs
 
 // Modules are used to group functions together
 // Indentation is needed for each nested module.
-module FunctionExamples = 
+module FunctionExamples =
 
     // define a simple adding function
     let add x y = x + y
-    
+
     // basic usage of a function
     let a = add 1 2
     printfn "1+2 = %i" a
-    
+
     // partial application to "bake in" parameters
     let add42 = add 42
     let b = add42 1
     printfn "42+1 = %i" b
-    
+
     // composition to combine functions
     let add1 = add 1
     let add2 = add 2
     let add3 = add1 >> add2
     let c = add3 7
     printfn "3+7 = %i" c
-    
+
     // higher order functions
     [1..10] |> List.map add3 |> printfn "new list is %A"
-    
+
     // lists of functions, and more
     let add6 = [add1; add2; add3] |> List.reduce (>>)
     let d = add6 7
@@ -158,54 +158,54 @@ module FunctionExamples =
 // ================================================
 
 // There are three types of ordered collection:
-// * Lists are most basic immutable collection. 
-// * Arrays are mutable and more efficient when needed. 
-// * Sequences are lazy and infinite (e.g. an enumerator). 
+// * Lists are most basic immutable collection.
+// * Arrays are mutable and more efficient when needed.
+// * Sequences are lazy and infinite (e.g. an enumerator).
 //
 // Other collections include immutable maps and sets
 // plus all the standard .NET collections
 
-module ListExamples = 
+module ListExamples =
 
-    // lists use square brackets 
+    // lists use square brackets
     let list1 = ["a";"b"]
     let list2 = "c" :: list1    // :: is prepending
     let list3 = list1 @ list2   // @ is concat
-    
+
     // list comprehensions (aka generators)
-    let squares = [for i in 1..10 do yield i*i] 
+    let squares = [for i in 1..10 do yield i*i]
 
     // prime number generator
     let rec sieve = function
         | (p::xs) -> p :: sieve [ for x in xs do if x % p > 0 then yield x ]
         | []      -> []
     let primes = sieve [2..50]
-    printfn "%A" primes 
-    
+    printfn "%A" primes
+
     // pattern matching for lists
-    let listMatcher aList = 
+    let listMatcher aList =
         match aList with
-        | [] -> printfn "the list is empty" 
-        | [first] -> printfn "the list has one element %A " first 
-        | [first; second] -> printfn "list is %A and %A" first second 
-        | _ -> printfn "the list has more than two elements"    
+        | [] -> printfn "the list is empty"
+        | [first] -> printfn "the list has one element %A " first
+        | [first; second] -> printfn "list is %A and %A" first second
+        | _ -> printfn "the list has more than two elements"
 
     listMatcher [1;2;3;4]
     listMatcher [1;2]
     listMatcher [1]
-    listMatcher []        
+    listMatcher []
 
     // recursion using lists
-    let rec sum aList = 
+    let rec sum aList =
         match aList with
         | [] -> 0
         | x::xs -> x + sum xs
     sum [1..10]
-    
-    // -----------------------------------------    
-    // Standard library functions 
+
+    // -----------------------------------------
+    // Standard library functions
     // -----------------------------------------
-    
+
     // map
     let add3 x = x + 3
     [1..10] |> List.map add3
@@ -213,68 +213,68 @@ module ListExamples =
     // filter
     let even x = x % 2 = 0
     [1..10] |> List.filter even
-    
+
     // many more -- see documentation
-    
-module ArrayExamples = 
+
+module ArrayExamples =
 
     // arrays use square brackets with bar
     let array1 = [| "a";"b" |]
     let first = array1.[0]        // indexed access using dot
-   
+
     // pattern matching for arrays is same as for lists
-    let arrayMatcher aList = 
+    let arrayMatcher aList =
         match aList with
-        | [| |] -> printfn "the array is empty" 
-        | [| first |] -> printfn "the array has one element %A " first 
-        | [| first; second |] -> printfn "array is %A and %A" first second 
-        | _ -> printfn "the array has more than two elements"    
+        | [| |] -> printfn "the array is empty"
+        | [| first |] -> printfn "the array has one element %A " first
+        | [| first; second |] -> printfn "array is %A and %A" first second
+        | _ -> printfn "the array has more than two elements"
 
     arrayMatcher [| 1;2;3;4 |]
 
     // Standard library functions just as for List
-   
-    [| 1..10 |] 
+
+    [| 1..10 |]
     |> Array.map (fun i -> i+3)
     |> Array.filter (fun i -> i%2 = 0)
     |> Array.iter (printfn "value is %i. ")
-    
-    
-module SequenceExamples = 
+
+
+module SequenceExamples =
 
     // sequences use curly braces
     let seq1 = seq { yield "a"; yield "b" }
-    
-    // sequences can use yield and 
+
+    // sequences can use yield and
     // can contain subsequences
     let strange = seq {
         // "yield! adds one element
         yield 1; yield 2;
-        
+
         // "yield!" adds a whole subsequence
-        yield! [5..10]  
+        yield! [5..10]
         yield! seq {
-            for i in 1..10 do 
+            for i in 1..10 do
               if i%2 = 0 then yield i }}
-    // test                
-    strange |> Seq.toList              
-              
+    // test
+    strange |> Seq.toList
+
 
     // Sequences can be created using "unfold"
     // Here's the fibonacci series
     let fib = Seq.unfold (fun (fst,snd) ->
         Some(fst + snd, (snd, fst + snd))) (0,1)
 
-    // test                        
+    // test
     let fib10 = fib |> Seq.take 10 |> Seq.toList
-    printf "first 10 fibs are %A" fib10     
-   
-    
+    printf "first 10 fibs are %A" fib10
+
+
 // ================================================
-// Data Types 
+// Data Types
 // ================================================
 
-module DataTypeExamples = 
+module DataTypeExamples =
 
     // All data is immutable by default
 
@@ -282,33 +282,33 @@ module DataTypeExamples =
     // -- Use a comma to create a tuple
     let twoTuple = 1,2
     let threeTuple = "a",2,true
-    
+
     // Pattern match to unpack
     let x,y = twoTuple  //sets x=1 y=2
 
-    // ------------------------------------ 
-    // Record types have named fields 
-    // ------------------------------------ 
+    // ------------------------------------
+    // Record types have named fields
+    // ------------------------------------
 
     // Use "type" with curly braces to define a record type
     type Person = {First:string; Last:string}
-    
-    // Use "let" with curly braces to create a record 
+
+    // Use "let" with curly braces to create a record
     let person1 = {First="John"; Last="Doe"}
 
     // Pattern match to unpack
     let {First=first} = person1    //sets first="john"
 
-    // ------------------------------------ 
+    // ------------------------------------
     // Union types (aka variants) have a set of choices
     // Only case can be valid at a time.
-    // ------------------------------------ 
+    // ------------------------------------
 
     // Use "type" with bar/pipe to define a union type
-    type Temp = 
+    type Temp =
         | DegreesC of float
         | DegreesF of float
-        
+
     // Use one of the cases to create one
     let temp1 = DegreesF 98.6
     let temp2 = DegreesC 37.0
@@ -317,29 +317,29 @@ module DataTypeExamples =
     let printTemp = function
        | DegreesC t -> printfn "%f degC" t
        | DegreesF t -> printfn "%f degF" t
-    
-    printTemp temp1 
+
+    printTemp temp1
     printTemp temp2
 
-    // ------------------------------------ 
+    // ------------------------------------
     // Recursive types
-    // ------------------------------------ 
+    // ------------------------------------
 
-    // Types can be combined recursively in complex ways 
+    // Types can be combined recursively in complex ways
     // without having to create subclasses
-    type Employee = 
+    type Employee =
       | Worker of Person
       | Manager of Employee list
 
     let jdoe = {First="John";Last="Doe"}
     let worker = Worker jdoe
-    
-    // ------------------------------------ 
+
+    // ------------------------------------
     // Modelling with types
-    // ------------------------------------ 
-    
+    // ------------------------------------
+
     // Union types are great for modelling state without using flags
-    type EmailAddress = 
+    type EmailAddress =
         | ValidEmailAddress of string
         | InvalidEmailAddress of string
 
@@ -350,40 +350,40 @@ module DataTypeExamples =
 
     // The combination of union types and record types together
     // provide a great foundation for domain driven design.
-    // You can create hundreds of little types that accurately 
+    // You can create hundreds of little types that accurately
     // reflect the domain.
 
     type CartItem = { ProductCode: string; Qty: int }
     type Payment = Payment of float
     type ActiveCartData = { UnpaidItems: CartItem list }
     type PaidCartData = { PaidItems: CartItem list; Payment: Payment}
-        
-    type ShoppingCart = 
+
+    type ShoppingCart =
         | EmptyCart  // no data
         | ActiveCart of ActiveCartData
-        | PaidCart of PaidCartData    
+        | PaidCart of PaidCartData
 
-    // ------------------------------------ 
+    // ------------------------------------
     // Built in behavior for types
-    // ------------------------------------ 
+    // ------------------------------------
 
     // Core types have useful "out-of-the-box" behavior, no coding needed.
     // * Immutability
     // * Pretty printing when debugging
     // * Equality and comparison
     // * Serialization
-        
+
     // Pretty printing using %A
-    printfn "twoTuple=%A,\nPerson=%A,\nTemp=%A,\nEmployee=%A" 
+    printfn "twoTuple=%A,\nPerson=%A,\nTemp=%A,\nEmployee=%A"
              twoTuple person1 temp1 worker
 
     // Equality and comparison built in.
     // Here's an example with cards.
     type Suit = Club | Diamond | Spade | Heart
-    type Rank = Two | Three | Four | Five | Six | Seven | Eight 
-                | Nine | Ten | Jack | Queen | King | Ace    
+    type Rank = Two | Three | Four | Five | Six | Seven | Eight
+                | Nine | Ten | Jack | Queen | King | Ace
 
-    let hand = [ Club,Ace; Heart,Three; Heart,Ace; 
+    let hand = [ Club,Ace; Heart,Three; Heart,Ace;
                  Spade,Jack; Diamond,Two; Diamond,Ace ]
 
     // sorting
@@ -391,27 +391,27 @@ module DataTypeExamples =
     List.max hand |> printfn "high card is %A"
     List.min hand |> printfn "low card is %A"
 
-             
+
 // ================================================
 // Active patterns
 // ================================================
 
-module ActivePatternExamples = 
+module ActivePatternExamples =
 
-    // F# has a special type of pattern matching called "active patterns" 
-    // where the pattern can be parsed or detected dynamically. 
+    // F# has a special type of pattern matching called "active patterns"
+    // where the pattern can be parsed or detected dynamically.
 
     // "banana clips" are the syntax for active patterns
-    
+
     // for example, define an "active" pattern to match character types...
-    let (|Digit|Letter|Whitespace|Other|) ch = 
+    let (|Digit|Letter|Whitespace|Other|) ch =
        if System.Char.IsDigit(ch) then Digit
        else if System.Char.IsLetter(ch) then Letter
        else if System.Char.IsWhiteSpace(ch) then Whitespace
-       else Other         
+       else Other
 
     // ... and then use it to make parsing logic much clearer
-    let printChar ch = 
+    let printChar ch =
       match ch with
       | Digit -> printfn "%c is a Digit" ch
       | Letter -> printfn "%c is a Letter" ch
@@ -424,52 +424,52 @@ module ActivePatternExamples =
     // -----------------------------------
     // FizzBuzz using active patterns
     // -----------------------------------
-    
+
     // You can create partial matching patterns as well
     // Just use undercore in the defintion, and return Some if matched.
     let (|MultOf3|_|) i = if i % 3 = 0 then Some MultOf3 else None
     let (|MultOf5|_|) i = if i % 5 = 0 then Some MultOf5 else None
 
     // the main function
-    let fizzBuzz i = 
+    let fizzBuzz i =
       match i with
-      | MultOf3 & MultOf5 -> printf "FizzBuzz, " 
-      | MultOf3 -> printf "Fizz, " 
-      | MultOf5 -> printf "Buzz, " 
+      | MultOf3 & MultOf5 -> printf "FizzBuzz, "
+      | MultOf3 -> printf "Fizz, "
+      | MultOf5 -> printf "Buzz, "
       | _ -> printf "%i, " i
-      
+
     // test
-    [1..20] |> List.iter fizzBuzz 
-    
+    [1..20] |> List.iter fizzBuzz
+
 // ================================================
-// Conciseness 
+// Conciseness
 // ================================================
 
-module AlgorithmExamples = 
+module AlgorithmExamples =
 
-    // F# has a high signal/noise ratio, so code reads 
+    // F# has a high signal/noise ratio, so code reads
     // almost like the actual algorithm
 
     // ------ Example: define sumOfSquares function ------
-    let sumOfSquares n = 
+    let sumOfSquares n =
        [1..n]              // 1) take all the numbers from 1 to n
        |> List.map square  // 2) square each one
        |> List.sum         // 3) sum the results
 
-    // test   
-    sumOfSquares 100 |> printfn "Sum of squares = %A" 
-       
-    // ------ Example: define a sort function ------  
+    // test
+    sumOfSquares 100 |> printfn "Sum of squares = %A"
+
+    // ------ Example: define a sort function ------
     let rec sort list =
        match list with
-       // If the list is empty   
-       | [] ->                            
+       // If the list is empty
+       | [] ->
             []                            // return an empty list
-       // If the list is not empty  
-       | firstElem::otherElements ->      // take the first element    
-            let smallerElements =         // extract the smaller elements    
+       // If the list is not empty
+       | firstElem::otherElements ->      // take the first element
+            let smallerElements =         // extract the smaller elements
                 otherElements             // from the remaining ones
-                |> List.filter (fun e -> e < firstElem) 
+                |> List.filter (fun e -> e < firstElem)
                 |> sort                   // and sort them
             let largerElements =          // extract the larger ones
                 otherElements             // from the remaining ones
@@ -479,13 +479,13 @@ module AlgorithmExamples =
             List.concat [smallerElements; [firstElem]; largerElements]
 
     // test
-    sort [1;5;23;18;9;1;3] |> printfn "Sorted = %A" 
+    sort [1;5;23;18;9;1;3] |> printfn "Sorted = %A"
 
 // ================================================
 // Asynchronous Code
 // ================================================
 
-module AsyncExample = 
+module AsyncExample =
 
     // F# has built-in features to help with async code
     // without encountering the "pyramid of doom"
@@ -495,23 +495,23 @@ module AsyncExample =
     open System.Net
     open System
     open System.IO
-    open Microsoft.FSharp.Control.CommonExtensions   
+    open Microsoft.FSharp.Control.CommonExtensions
 
     // Fetch the contents of a URL asynchronously
-    let fetchUrlAsync url =        
-        async {   // "async" keyword and curly braces 
+    let fetchUrlAsync url =
+        async {   // "async" keyword and curly braces
                   // creates an "async" object
-            let req = WebRequest.Create(Uri(url)) 
-            use! resp = req.AsyncGetResponse()    
+            let req = WebRequest.Create(Uri(url))
+            use! resp = req.AsyncGetResponse()
                 // use! is async assignment
-            use stream = resp.GetResponseStream() 
+            use stream = resp.GetResponseStream()
                 // "use" triggers automatic close()
                 // on resource at end of scope
-            use reader = new IO.StreamReader(stream) 
-            let html = reader.ReadToEnd() 
-            printfn "finished downloading %s" url 
+            use reader = new IO.StreamReader(stream)
+            let html = reader.ReadToEnd()
+            printfn "finished downloading %s" url
             }
-            
+
     // a list of sites to fetch
     let sites = ["http://www.bing.com";
                  "http://www.google.com";
@@ -520,7 +520,7 @@ module AsyncExample =
                  "http://www.yahoo.com"]
 
     // do it
-    sites 
+    sites
     |> List.map fetchUrlAsync  // make a list of async tasks
     |> Async.Parallel          // set up the tasks to run in parallel
     |> Async.RunSynchronously  // start them off
@@ -529,58 +529,58 @@ module AsyncExample =
 // .NET compatability
 // ================================================
 
-module NetCompatibilityExamples = 
+module NetCompatibilityExamples =
 
     // F# can do almost everything C# can do, and it integrates
     // seamlessly with .NET or Mono libraries.
 
     // ------- work with existing library functions  -------
-    
+
     let (i1success,i1) = System.Int32.TryParse("123");
     if i1success then printfn "parsed as %i" i1 else printfn "parse failed"
 
     // ------- Implement interfaces on the fly! -------
-    
+
     // create a new object that implements IDisposable
-    let makeResource name = 
-       { new System.IDisposable 
+    let makeResource name =
+       { new System.IDisposable
          with member this.Dispose() = printfn "%s disposed" name }
 
-    let useAndDisposeResources = 
+    let useAndDisposeResources =
         use r1 = makeResource "first resource"
-        printfn "using first resource" 
+        printfn "using first resource"
         for i in [1..3] do
             let resourceName = sprintf "\tinner resource %d" i
-            use temp = makeResource resourceName 
-            printfn "\tdo something with %s" resourceName 
+            use temp = makeResource resourceName
+            printfn "\tdo something with %s" resourceName
         use r2 = makeResource "second resource"
-        printfn "using second resource" 
-        printfn "done." 
+        printfn "using second resource"
+        printfn "done."
 
     // ------- Object oriented code -------
-    
+
     // F# is also a fully fledged OO language.
     // It supports classes, inheritance, virtual methods, etc.
 
     // interface with generic type
-    type IEnumerator<'a> = 
+    type IEnumerator<'a> =
         abstract member Current : 'a
-        abstract MoveNext : unit -> bool 
+        abstract MoveNext : unit -> bool
 
     // abstract base class with virtual methods
     [<AbstractClass>]
-    type Shape() = 
+    type Shape() =
         //readonly properties
         abstract member Width : int with get
         abstract member Height : int with get
         //non-virtual method
         member this.BoundingArea = this.Height * this.Width
         //virtual method with base implementation
-        abstract member Print : unit -> unit 
+        abstract member Print : unit -> unit
         default this.Print () = printfn "I'm a shape"
 
-    // concrete class that inherits from base class and overrides 
-    type Rectangle(x:int, y:int) = 
+    // concrete class that inherits from base class and overrides
+    type Rectangle(x:int, y:int) =
         inherit Shape()
         override this.Width = x
         override this.Height = y
@@ -590,20 +590,20 @@ module NetCompatibilityExamples =
     let r = Rectangle(2,3)
     printfn "The width is %i" r.Width
     printfn "The area is %i" r.BoundingArea
-    r.Print()        
+    r.Print()
 
     // ------- extension methods  -------
-        
+
     //Just as in C#, F# can extend existing classes with extension methods.
     type System.String with
        member this.StartsWithA = this.StartsWith "A"
 
     //test
     let s = "Alice"
-    printfn "'%s' starts with an 'A' = %A" s s.StartsWithA    
-    
+    printfn "'%s' starts with an 'A' = %A" s s.StartsWithA
+
     // ------- events  -------
-   
+
     type MyButton() =
         let clickEvent = new Event<_>()
 
@@ -615,11 +615,11 @@ module NetCompatibilityExamples =
 
     // test
     let myButton = new MyButton()
-    myButton.OnClick.Add(fun (sender, arg) -> 
+    myButton.OnClick.Add(fun (sender, arg) ->
             printfn "Click event with arg=%O" arg)
 
     myButton.TestEvent("Hello World!")
-        
+
 ```
 
 ## More Information