Functional Programming and/or F# Conferences

There are some conferences I've noticed for year 2013. I will update this page regularly.

• A conference for Functional programmers, Chicago, USA, July 8 - 10, 2013
• Data Driven Functional Programming Workshop 2013, Rome, Italy, Jan 22, 2013
• The 18th ACM SIGPLAN International Conference on Functional Programming, Boston, USA, Sep 25 - 27, 2013
• Functional Program eXchange 2013, London, UK, March 15, 2013
• TFP 2013, Provo, Utah, USA, May 14 - 16, 2013
• Norwegian Developer Conference (NDC), Oslo, Norway, Jun 12 - 14, 2013
• Progressive F# Tutorials 2013, London, UK, Oct 31 - Nov 1, 2013
• Lambda Jam, May 16-17, 2013 at the Translink Centre for Service Excellence in the vibrant urban village of Kelvin Grove, just minutes from the Brisbane CBD
• POPL 2013: 40th ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages, Jan 23-25, Rome, Italy
• Strangeloop - September 18..20, St Louis
• ICFP - September 25..27, Boston
• GOTO Aarhus - September 30..October 2, Denmark
• GOTO Berlin - October 17..18, Germany
• Øredev - November 4..8, Sweden

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Self Note: Get Replication status

The following script is to find the error within recent 30 min.


use distribution;
go
select
case
when COUNT(*)>0 then 'there are error for replication during the last half hour'
else 'no error found'
end
from msrepl_errors
where [time] > DATEADD(MINUTE, -30, GETDATE())
go

Azure Database Full

I blow up the 1G web-version database. After I delete, I still cannot insert record. :-(

After check the space used by using

select sum(reserved_page_count) * 8.0 / 1024 

from sys.dm_db_partition_stats

I find the space is still occupied. After run the rebuild index: alter index all on myTable rebuild, the space is reclaimed.

Debug F# Type Provider

Recently I am trying to use Type Provider (TP) in our production code. The first question I got is how to debug TP. The following is a way to debug it.

• download the type provider template or create your own project using the type provider API from codeplex.
• create a F# console Application in the solution
• from the F# console application add reference to the type provider project. Let us call this project ConsoleApplication2
• go to type provider project
• right click the project and open the project property
• find the "Debug" tab in the project property
• set the property like the image shown below:

•  Set the type provider project as start up project.

When the type provider project starts, it starts visual studio to open the Console application. You can put your break point in the type provider code. Once the debug is finished, the Visual Studio is closed and you are free to modify your code and rebuild the type provider code.

This approach does not requires to close and reopen the Visual Studio.

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Self Note: SQL Azure + SSIS

I have been stuck with SQL Azure with SQL Server SSIS. My SSIS package needs to transfer data from SQL Server to SQL Azure. Everything seems working correctly until I set the "Required" field on the transaction. I get wired error indicate me that AcquireConnection failure is happening on the OLE DB during the validation period. The reason is very simple, SQL Server does not support DTC!

The SSIS package has to be executed on the SQL server. If the SSIS package is executed on a third server, the transaction is not supported and the AcquireConnection fails on OLE DB.

Remove F# snippet shortcut

I got email from Jack two weeks ago. He said F# code snippet is "too active". Yes, when you type, some shortcut keys will pop up and this is very annoying. The quick (and probably dirty) fix is to remove the shortcut key in the snippet file. The script file to remove the shortcut key is listed below. You can run it targeting to the snippet folder. Usually the folder is My Document \ < Visual Studio Folder > \Code Snippets\Visual F#.

If you are curious where is is the Shortcut key in the snippet file. Here is the screenshot.

The latest version snippets on the codeplex project does not have any shortcut key. You can download these snippets from codeplex project as well.

Although the shortcut key is removed, you still use Ctrl+K,X to show the snippet dialog.

 let (|ValidFolder|_|) folder =   
   match folder with  
   | _ when (File.GetAttributes(folder) &&& FileAttributes.Directory = FileAttributes.Directory) -> Some ValidFolder  
   | _ -> None  

 let removeShortcutTag (xmlFile:string) =   
   let doc = XDocument.Load xmlFile  
   doc.Descendants()  
   |> Seq.tryFind (fun decendent -> decendent.Name.LocalName = "Shortcut")  
   |> function  
     | Some node ->   
       File.SetAttributes (xmlFile, ~~~FileAttributes.ReadOnly  
                      &&& ~~~FileAttributes.Hidden  
                      &&& ~~~FileAttributes.System)  
       node.Value <- String.Empty  
       doc.Save(xmlFile)  
     | None -> ()  

 let processXMLFiles folder =   
   let xmlFiles = Directory.GetFiles(folder, "*.snippet")  
   xmlFiles  
   |> Seq.iter (fun xmlFile -> removeShortcutTag xmlFile)  

 let rec processXML folder =   
   match folder with  
   | ValidFolder ->   
     let subFolders = Directory.EnumerateDirectories(folder)  
     processXMLFiles folder  
     subFolders  
     |> Seq.iter processXML  
   | _ -> ()  

 processXML @"C:\MyCode\fsharpcodesnippet"  

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F# Contract Position

Please contact recruiter directly. 

• ·         .Net (3.5 or 4.0) F# or C# programming expertise required
• In depth understanding of object-oriented analysis and design with a broad understanding of software design patterns preferred
• Understanding of IT in Financial Services background & domain knowledge –equity, fixed income, credit and derivatives products preferred
• ·         Experience in working in a fast paced, front-middle office or Risk/Margin preferred
• Experience in working with Middleware components such as Solace, Tibco RV, EMS preferred. XML, data binding and SOAP web services a plus

Self starter, passionate and enthusiastic attitude.

This is an Immediate need.

ONLY US CITIZENS PLEASE.... 

Srikanth Mandapati

HuMetis Technologies Inc

2 King Arthur Court

Lakeside W A-1

North Brunswick, NJ 08902

Phone: (609) 910-3391

Fax: (877) 451-5544

Web: http://www.humetis.com

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F# Computational Expression Sample - File System + XML

Although I am not a PowerShell fan, I do like one feature of PowerShell. You can easily go from file system to registry. PowerShell treat file system and registry are same thing. I am afraid I have to face some Azure Virtual Machine management tasks in the future and I need to prepare in advance.

The following Computational Expression (CE) is a way to design an embedded language like PowerShell. I do not want to risk my computer's registry so I choose the File system and XML file. If you use cd "my path", it goes to either folder, file, or XML file's node or attribute.

the file system is like

and the XML file is

 // Learn more about F# at http://fsharp.net  
 // See the 'F# Tutorial' project for more help.  
 open System  
 open System  
 open System.Xml.Linq  
 type UnifiedType =   
   | Directory of string  
   | XMLFile of string  
   | Node of XElement * UnifiedType  
   | Attribute of string * XAttribute * UnifiedType  
 let rec getElement currentType (path:string list) =   
   match path with  
   | [] ->   
     currentType  
   | head::tail ->  
     let node =   
       match currentType with  
       | Directory(dir) ->   
         let dirs = System.IO.Directory.GetDirectories(dir)  
         match dirs |> Seq.tryFind (fun n -> n.EndsWith head) with  
         | Some n -> Directory(System.IO.Path.Combine(n))  
         | _ ->   
           let files = System.IO.Directory.GetFiles(dir, "*.xml")  
           match files |> Seq.tryFind (fun file ->   
                           String.Compare(System.IO.Path.GetFileName(file), head, true)=0) with  
           | Some n -> XMLFile(n)  
           | _ -> failwithf "cannot find %s" dir       
       | XMLFile (name) ->  
         let doc = XDocument.Load(name)  
         match (doc.Descendants()) |> Seq.tryFind (fun n -> n.Name.LocalName=head) with  
         | Some n -> Node(n, currentType)  
         | _ -> failwithf "cannot find %s" name    
       | Node(node, fn) ->  
         match (node.Descendants()) |> Seq.tryFind (fun n -> n.Name.LocalName=head) with  
         | Some n -> Node(n, fn)  
         | _ ->   
           match (node.Attributes()) |> Seq.tryFind(fun n -> n.Name.LocalName=head) with  
           | Some n -> Attribute(n.Name.LocalName, n, fn)  
           | _ -> failwithf "cannot find %s" node.Name.LocalName    
       | Attribute(name, value, fn) ->   
         failwithf "cannot find %s" name  
     getElement node tail  
 let setValue point (v:string) =   
   match point with  
   | Attribute (name, value, XMLFile(fn)) ->   
     value.Value <- v  
     value.Document.Save(fn)  
   | _ -> ()  
 type ExtendedFileSystem(startPoint:UnifiedType) =   
   member this.Yield( () ) = startPoint  
   [<CustomOperation("cd")>]  
   member this.GoDown(point:UnifiedType, id:string) =   
     getElement point [id]  
   [<CustomOperation("set")>]  
   member this.Set(point:UnifiedType, v:string) =   
     setValue point v  
     point  
   member this.Run(point:UnifiedType) =   
     fun () -> point  
 let fileSystem = ExtendedFileSystem(Directory(@".\"))  
 let fs =   
   fileSystem {  
     cd "Data"  
     cd "Xml"  
     cd "XmlFile1.xml"  
     cd "Xml"  
     cd "Data"  
     cd "A"  
     set "17" }  
 printfn "%A" ( fs() )  
 ignore <| System.Console.ReadKey()  

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My First SSIS + Azure SQL Task

I need to do a task transferring data from SQL Server to Azure cloud. And this is really a good opportunity to refresh my SQL skill. One of my co-workers Haitao, who is really expert in SQL, demonstrates the SSIS. I love the way it processes data.

The core of the task is to transfer the data from SQL to SQL Azure. So the first task is to find the data flow task. I am a visual person, the colorful icon make it stands up and very easy to find out. Two yellow dots with a green arrow. :-)

Once you double click the Data Flow task on the design surface. You have to provide source and target. I had trouble using ADO.net when I set up the configuration file, so I use the OLE DB tasks whenever it is possible.

I need to create several tasks. Another lesson I learnt is the arrow between tasks are "precedence". If a node's proceeding tasks are all finished, this tasks can start right way. So you might see some tasks are executed simultaneously. 

Variable is what I I use exchange the statements from one task to the other task(s). I use select count(*) to check the existence of a table and result is put into a variable.

Be very careful, if it is ADO.net, the result uses index. For example, your SQL statement is select count(*) as AA from TableAA. OLE DB allow you use AA in the result set, but ADO.net only accept 0. This costs me 1 hour.. :(

Because the development environment is different from production environment, I have to make a configuration file. The configuration file can be created by right click anywhere on the design surface (not on any tasks). The right-click menu has the "Package configurations..." item. The connection string is what I wanted to put in the configuration file. The wizard does not put the password in the configuration file, so every time I made changes to the configuration file I had to manually add the password in the connection string.

After I successfully put the connection string into the configuration file, I tried to push the limit by dynamically generate SQL statement from the variable stored in the configuration file. The following screen shot should solve the problem pretty easy. 

Overall, I am very happy about the SSIS and its tooling support. Well, my stomach is really empty. I will blog next time.