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--- projects:fsharp_workshop [2015/04/17 23:03] – mkucia
+++ projects:fsharp_workshop [2015/05/02 12:45] (current) – [hello(x)] mkucia
@@ Line 1: / Line 1: @@
 ====== F# workshop ======
+{{:projects:fsharp_logo.png?nolink|}}
 ===== Prerequisites =====
     * https://www.linqpad.net/ or anything that can execute a REPL((Read, Evaluate, Print Loop))
@@ Line 22: / Line 22: @@
 hello
 </code>
+F# (pronounced “F Sharp”) is
+<WRAP group>
+<WRAP half column box>
+  * Open Source
+  * Multi platform
+  * Modern, rising popularity
+  * Lazy evaluated
+  * Reusable
+  * Concise (See [[http://theburningmonk.com/2014/12/seven-ineffective-coding-habits-many-f-programmers-dont-have/|signal-to-noise ratio]])
+  * Strongly typed
+  * Functional first
+    * Use functional to write easy to test and understand code
+    * Use imperative for performance and compatibility
+    * Use objective for organization and encapsulation
+  * Compiled
+</WRAP>
+<WRAP half column box>
+  * Not suitable for real time (unpredictable performance)
+  * Hard to optimize (Functional languages fundamentally don't model how your computer works)
+  * Functional first (different thinking process, you will need to re-learn)
+</WRAP>
+</WRAP>
+programming language for writing simple code to solve complex problems.
 <code fsharp>
@@ Line 28: / Line 54: @@
 </code>
+Introducing pipeline operator:
 <code fsharp>
 let hello x = printfn "Hello %s" x
 "World" |> hello
 </code>
-''|>'' is the pipeline operator
+<hidden pipeline operator definition>
+How to define the operator?
+<code fsharp>
+let inline (|>) x f = f x
+</code>
+</hidden>
 <code fsharp>
@@ Line 57: / Line 90: @@
 </code>
-===== Why? =====
+Note that F# uses indentation to indicate block structure. Find out more [[http://fsharpforfunandprofit.com/posts/fsharp-syntax/|here]].
-<WRAP group>
+===== Getting data =====
-<WRAP half column box>
-Pros:
-  * Open Source
-  * Multi platform (Mono, .NET core)
-  * Modern, rising popularity
-  * Lazy evaluation
-  * Reusable
-  * Reduced code (See [[http://theburningmonk.com/2014/12/seven-ineffective-coding-habits-many-f-programmers-dont-have/|signal-to-noise ratio]])
-  * Strongly typed
-</WRAP>
-<WRAP half column box>
+The following example loads data from webpage and stores it in CSV file.
-Cons:
-  * Not suitable for real time (unpredictable performance)
+<hidden>
-  * Functional languages fundamentally don't model how your computer works ⇒ harder to optimize.
+<code fsarp>
-  * Different thinking process (you need to re-learn)
+open System.Net
-</WRAP>
+open System
-</WRAP>
+open System.IO
+let myURL = @"..."
+let fetchUrl callback url =
+    let req    = WebRequest.Create(Uri(url))
+    use resp   = req.GetResponse()
+    use stream = resp.GetResponseStream()
+    use reader = new IO.StreamReader(stream)
+    callback reader url
+let myCallback (reader:IO.StreamReader) url =
+    let htmlSource = reader.ReadToEnd()
+    htmlSource
+let getWebpageHTML = fetchUrl myCallback myURL
+type FirstOrLast =
+	| GetFirst
+	| GetLast
+let getDataFromHTML (rawHTML:String) =
+	let split (split_point:String) (firstOrLast:FirstOrLast) (text:String) =
+		let array = text.Split([|split_point|], 2, StringSplitOptions.RemoveEmptyEntries)
+		match firstOrLast with
+		| GetFirst -> array.First()
+		| GetLast  -> array.Last()
+	rawHTML
+	|> split @"<table id=""t2"">" GetLast
+	|> split @"</table>"          GetFirst
+let removeAllTags text =
+    Regex.Replace(text, "<.*?>", String.Empty);
+let getCSVfromHTML rawHTML =
+	let mutable (text:String) = String.Empty
+	text <- rawHTML
+	text <- text.Replace(@"</th>", ";");
+	text <- text.Replace(@"</td>", ";");
+	text <- text.Replace(@"</tr>", Environment.NewLine);
+	text <- text.Replace(',', '|');
+	text <- text.Replace('.', ',');
+	text <- removeAllTags text
+	text
+let CSVresult = getCSVfromHTML (getDataFromHTML getWebpageHTML)
+CSVresult.Dump()
+</code>
+</hidden>
+> An F# **type provider** is a component that provides types, properties, and methods for use in your program.
+> The key to information-rich programming is to eliminate barriers to working with diverse information sources. One significant barrier to including a source of information into a program is the need to represent that information as types, properties, and methods for use in a programming language environment.
+> Writing these types manually is very time-consuming and difficult to maintain. A common alternative is to use a code generator which adds files to your project; however, the conventional types of code generation do not integrate well into exploratory modes of programming supported by F# because the generated code must be replaced each time a service reference is adjusted.
 ===== References =====
   * http://fsharp.org/