Why Functional Programming Matters?

Dated, but a highly recommended reading for functional programmers by John Hughes of Institutionen  Datavetenskap,

 

Abstract: As software becomes more and more complex, it is more and more important to structure it well. Well-structured software is easy to write, easy to debug, and provides a collection of modules that can be re-used to reduce future programming costs. Conventional languages place conceptual limits on the way problems can be modularised. Functional languages push those limits back. In this paper we show that two features of functional languages in particular, higher-order functions and lazy evaluation, can contribute greatly to modularity. As examples, we manipulate lists and trees, program several numerical algorithms, and implement the alpha-beta heuristic (an algorithm from Artificial Intelligence used in game-playing programs). Since modularity is the key to successful programming, functional languages are vitally important to the real world.

The paper is available as postscript and pdf.  - Why Functional Programming Matters

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Resolution for the group's SID could not be resolved Error

I have recently encountered the following error when enumerating through the UserPrincipal.GetAuthorizationGroups collection.

System.DirectoryServices.AccountManagement.PrincipalOperationException: An error (1301) occurred while enumerating the groups.  The group's SID could not be resolved.

The problem was introduction of the domain controller running Server 2012 while the machine running my application was win7 VM (applies to Win2K8 as well)

7536.errorMessage3

With little googling, it appears that for the Windows 7 VM with introduction of 2012 domain controller, this SID error appears to be a known issue. When a 2012 domain controller is involved, the GetAuthorizationGroups() function would fail on groups (SIDs) that are added to a user by default.

Installing KB2830145 fixed my problem.

References

 

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[Book Review] Angular JS Services

Angular JS services by Jim Levin is a delightful addition to a topic which isn’t discussed as much as the framework itself. Angular, as a powerful structural framework for dynamic web apps has been topic of various well publicized texts. However the services, which provide the core of backend functionality, don’t get much lime-light. c’est la vie.

 

download

In Angular, services are designed as substitutable objects that are wired together using dependency injection (DI); therefore the understanding of law of demeter is quite important. Author started with fundamentals without much ado, and seamlessly transitioned into discussion about testability, mocking, data management and business logic handling. Handling cross cutting concerns (chapter 4) and Mash-ups (chapter 6) are especially interesting topics. BDD using Jasmine spies (test doubles) is also a treat for behavior-driven development fans.

The notion of designing services, tenets, best practices and architecting services for testability are topics every developer should pay attention to. Levin discusses service building best practices, factories and providers in a concrete and concise fashion with easy to understand code samples.

angular-js-logo

The book assumes that one is already familiar with JavaScript and have some experience writing applications using Angular. The quality of print vs. cost is a letdown; I hope it improves in next editions.

[Disclaimer] I have received the review copy from the publisher.

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Teaching Functional Programming to Professional .NET Developers

An informative paper by Tomas Petricek of University of Cambridge.

Abstract. Functional programming is often taught at universities to first-year or second-year students and most of the teaching materials have been written for this audience. With the recent rise of functional programming in the industry, it becomes important to teach functional concepts to professional developers with deep knowledge of other paradigms, most importantly object-oriented. We present our experience with teaching functional programming and F# to experienced .NET developers through a book Real-World Functional Programming and commercially offered F# trainings. The most important novelty in our approach is the use of C# for relating functional F# with object-oriented C# and for introducing some of the functional concepts. By presenting principles such as immutability, higher-order functions and functional types from a different perspective, we are able to build on existing knowledge of professional developers. This contrasts with a common approach that asks students to forget everything they know about programming and think completely differently. We believe that our observations are relevant for trainings designed for practitioners, but perhaps also for students who explore functional relatively late in the curriculum.

 

 

Honorable mention to A Look at F# from C#’s corner 

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Poodle & Sandworm

In lieu of recently passed National Cyber Security Awareness Month, a shout out to CVE-2014-4114 with MS14-060 as a vulnerability in the OLE package manager can be exploited to remotely execute arbitrary code in Microsoft Windows versions Vista SP2 to Windows 8.1 and in Server 2008 and 2012. Yeah, 2012 too.

and here is to poodle.

POODLE: This dog bites – An infographic by the team at Pluralsight

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GAC Changes in Windows Server 2012

Prior to Windows Server 2012, gacutil is typically used to install DLL files in the Windows Global Assembly Cache (GAC). With Windows Server 2012 unfortunately it's not quite so easy. Being able to simply open the GAC in Explorer and drag/drop is gone (so yeah, no shell!). Also GacUtil.exe is not present on the server by default as part of runtime. In order to use gacutil like earlier versions of Windows, we would need to install the .NET SDK on the server which is not really a good idea (defense in depth; only have runtime on server). Of course copying-pasting gacutil.exe doesn’t work (dependencies).

Since we are all too familiar to.NET versions prior to 4.0, GAC used to be in the c:\windows\assembly window and had a custom shell extension to flatten the directory structure into a list of assemblies. Like mentioned earlier, the shell extension is no longer used for .NET versions 4.0 and up. Since we have .NET 4.5 on server machines, its GAC is stored in c:\windows\microsoft.net\assembly. You just get to see the actual directory structure. Locating the assembly isn't that difficult, start in the GAC_MSIL directory and you should have no trouble locating your assembly there by its name. Locate the folder with the same display name as your assembly. It will have a subdirectory that has an unspeakable name that's based on the version and public key token, that subdirectory contains the DLL.

Therefore, PowerShell is the recommended approach to do the GAC install. Following are the instructions on how to install the dll to GAC in Windows 2012 Server. For EL6, we ended up writing the following powershell script.

Set-location "C:\tmp"
 [System.Reflection.Assembly]::Load("System.EnterpriseServices, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a")
 $publish = New-Object System.EnterpriseServices.Internal.Publish
 $publish.GacInstall("c:\tmp\Microsoft.Practices.EnterpriseLibrary.Common.dll")
 $publish.GacInstall("c:\tmp\Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.dll")
 $publish.GacInstall("c:\tmp\Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.Logging.dll")
 $publish.GacInstall("c:\tmp\Microsoft.Practices.EnterpriseLibrary.ExceptionHandling.WCF.dll")
 $publish.GacInstall("c:\tmp\Microsoft.Practices.EnterpriseLibrary.Logging.dll")

Happy Coding!

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WCF Handling Nested Attributes in AttributeGroup

tldr; SVCUtil does not Generate Code for Nested Attributes in AttributeGroup; here is the code (github repo) and explanation of a workaround.

Beyond Controlled HelloWorld() samples, interoperability standards are not black and white, rather a process that has shades of gray. If you've worked on consuming 3rd party 'enterprise' API's, you may have encountered problems with flattening of WSDL’s, or when generating a service proxy using svcutil.exe, noticed that not all attribute groups gets generated.  For instance, an attributeGroup wrapping another which contains attributes, those attributes will NOT be generated.

I tried a few things like using the DataContractSerializer but it appears that the attributeGroup is ignored by design. The only workaround appears to be removing the extra attributeGroup wrapping. DataContractSerializer does not recognize the attributeGroup (see Data Contract Schema Reference) and as you have already noticed, Xsd (essentially the XmlSerializer) does not recognize nested attributeGroups.

One Reference workaround that is described here, essentially asks you to replace the attributeGroup elements with the actual attributes.

For example:

<xs:attributeGroup name="myAttributeGroup">
<xs:attribute name="someattribute1" type="xs:integer"/>
<xs:attribute name="someattribute2" type="xs:string"/>
</xs:attributeGroup>

<xs:complexType name="myElementType">
<xs:attributeGroup ref="myAttributeGroup"/>
</xs:complexType>

should be transformed into:

<xs:complexType name="myElementType">
<xs:attribute name="someattribute1" type="xs:integer"/>
<xs:attribute name="someattribute2" type="xs:string"/>
</xs:complexType>

To do this in a repeatable manner, following code provides a good starting point on how to handle the attributeGroup issue. Here is a before and after screenshot of WSDL's.

SVCUtil does not Generate Code for Nested Attributes in AttributeGroup

 

I created a small C# app to transform the data, and then run svcutil to generate the WSDL. essentially replacing all instances of <attributeGroup ref=”xxx”> with the definitions of <attributeGroupname=”xxx”>, just as described in the link that I provided earlier.

XDocument wsdl = XDocument.Load(inputFile);

IEnumerable<XElement> attributeGroupDefs =
wsdl.Root.Descendants("{http://www.w3.org/2001/XMLSchema}attributeGroup")
.Where(w => w.Attribute("name") != null)
.Select(x => x);

foreach (
XElement r in
wsdl.Root.Descendants("{http://www.w3.org/2001/XMLSchema}attributeGroup")
.Where(w => w.Attribute("ref") != null))
{
string refValue = r.Attribute("ref").Value;

foreach (XElement d in attributeGroupDefs)
{
string defValue = d.Attribute("name").Value;
if (refValue == defValue)
{
IEnumerable<XElement> s =
d.Elements("{http://www.w3.org/2001/XMLSchema}attribute").Select(x => x);
foreach (XElement e in s)
{
r.AddBeforeSelf(e);
}
break;
}
}
}

wsdl.Root.Descendants("{http://www.w3.org/2001/XMLSchema}attributeGroup")
.Where(w => w.Attribute("ref") != null)
.Remove();
wsdl.Save(outFile);

 

This may require some more tweaking, but it appears have corrected all / most of the attributeGroup issues (I only spot checked this).

Happy Coding!

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Dissertation - Done!

Screen Shot 2014-08-26 at 10.37.48 AM

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P≠NP - A Definitive Proof by Contradiction

Following the great scholarly acceptance and outstanding academic success of "The Clairvoyant Load Balancing Algorithm for Highly Available Service Oriented Architectures, this year I present P Not Equal to NP - A Definitive Proof by Contradiction.

 

P Not Equal to NP - A Definitive Proof by Contradiction

 

Click here to read the entire paper in PDF. P Not Equal to NP - A Definitive Proof by Contradiction.

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LyX/LaTeX formatting for the C# code

If you are googling trying to find a good way to insert C# code in LyX, this is where you'd probably end up. MaPePer has provided a very good solution; I have modified it slightly (hiding tabs and removing comments) and following is illustration on how to use it in LyX.

First thing you'd need is a Lyx document (LyxC#CodeListing.lyx). Empty one works well.

Add the following to Preamble (Document-> Settings-> LaTeX Preamble)

\usepackage{color}
\usepackage{listings}

\lstloadlanguages{% Check Dokumentation for further languages ...
C,
C++,
csh,
Java
}

\definecolor{red}{rgb}{0.6,0,0} % for strings
\definecolor{blue}{rgb}{0,0,0.6}
\definecolor{green}{rgb}{0,0.8,0}
\definecolor{cyan}{rgb}{0.0,0.6,0.6}

\lstset{
language=csh,
basicstyle=\footnotesize\ttfamily,
numbers=left,
numberstyle=\tiny,
numbersep=5pt,
tabsize=2,
extendedchars=true,
breaklines=true,
frame=b,
stringstyle=\color{blue}\ttfamily,
showspaces=false,
showtabs=false,
xleftmargin=17pt,
framexleftmargin=17pt,
framexrightmargin=5pt,
framexbottommargin=4pt,
commentstyle=\color{green},
morecomment=[l]{//}, %use comment-line-style!
morecomment=[s]{/*}{*/}, %for multiline comments
showstringspaces=false,
morekeywords={ abstract, event, new, struct,
as, explicit, null, switch,
base, extern, object, this,
bool, false, operator, throw,
break, finally, out, true,
byte, fixed, override, try,
case, float, params, typeof,
catch, for, private, uint,
char, foreach, protected, ulong,
checked, goto, public, unchecked,
class, if, readonly, unsafe,
const, implicit, ref, ushort,
continue, in, return, using,
decimal, int, sbyte, virtual,
default, interface, sealed, volatile,
delegate, internal, short, void,
do, is, sizeof, while,
double, lock, stackalloc,
else, long, static,
enum, namespace, string},
keywordstyle=\color{cyan},
identifierstyle=\color{red},
}
\usepackage{caption}
\DeclareCaptionFont{white}{\color{white}}
\DeclareCaptionFormat{listing}{\colorbox{blue}{\parbox{\textwidth}{\hspace{15pt}#1#2#3}}}
\captionsetup[lstlisting]{format=listing,labelfont=white,textfont=white, singlelinecheck=false, margin=0pt, font={bf,footnotesize}}

 

In the preamble (Document-> Settings-> LaTeX Preamble)
preamble

 

Now add a program listing block. Hopefully you have the listing package installed otherwise you can always use the listing MikTeX update.

 

insert-program-listing-lyx


Now add the code to the listing block.


lyx-screen

and then Ctrl-R

 

CodeListing

 

Tada!

 

Happy Lyxing

 

References & download LyxC#CodeListing.lyx

 

 

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