Rash thoughts about .NET, C#, F# and Dynamics NAV.

Since version 0.12 the FAKE build system provides an easy way to setup build configurations for CruiseControl.NET.

“CruiseControl.NET is an Automated Continuous Integration server, implemented using the Microsoft .NET Framework.”

[thoughtworks.org]

In this article I will show you how you can set up a FAKE build script in CruiseControl.NET. We will use the CalculatorSample which you can download from the FAKE Download page.

If you want to know how this build script works and how you could create one for your own projects please read the “Getting started with FAKE”-tutorial.

If you want to set up “FAKE – F# Make” build configurations in TeamCity please read “Integrating a "FAKE – F# Make" build script into TeamCity”.

Installing CruiseControl.NET

You can download CruiseControl.NET from thoughtworks.org. After the installation process (further instructions) you should see an empty dashboard:

Installing Subversion

The CalculatorSample is using Subversion (SVN) for SourceControl, so we need to download SVN from subversion.tigris.org. I’m using the “Windows MSI installer with the basic win32 binaries” and installed them under “c:\Program Files (x86)\Subversion\”.

Installing FxCop

The CalculatorSample is using FxCop, so we need to download and install it next.

“FxCop is an application that analyzes managed code assemblies (code that targets the .NET Framework common language runtime) and reports information about the assemblies, such as possible design, localization, performance, and security improvements. Many of the issues concern violations of the programming and design rules set forth in the Design Guidelines for Class Library Developers, which are the Microsoft guidelines for writing robust and easily maintainable code by using the .NET Framework.”

[MSDN]

Creating a FAKE Project

Now create a new folder for the CalculatorSample sources. I’m using “d:\Calculator\” for the rest of the article.

The next step is to modify the CruiseControl.NET config file (“c:\Program Files (x86)\CruiseControl.NET\server\ccnet.config” on my machine):

In this configuration I set up a trigger which checks every 30 sec. for changes in my CalculatorSample project.

If SVN finds changes FAKE.exe is called with my build script (completeBuild.fsx).

After the build I want to merge the FxCop and NUnit output files with my build results to create a build report.

Configuring the dashboard

In order to provide a nicer output on the dashboard we need to modify the BuildPlugins section in the dashboard.config file (“c:\Program Files (x86)\CruiseControl.NET\webdashboard\dashboard.config” on my machine):

As you can see we use the nant.xsl to transform the FAKE output to HTML.

Starting the build

Now if everything is configured correctly, you can tell CruiseControl.NET to run your build (press “Start” for your build project on the dashboard):

Now CruiseControl.NET should use SVN to checkout the CalculatorSample sources and run the build. The output on the project page for build 1 should look like this:

You can also inspect the NUnit and FxCop results:

Please feel free to give feedback if you have any problems with this article.

I just released a new version of my Open Source Build Automation Framework “FAKE – F# Make”. You can read more about FAKE on the project website or in the Getting started with "FAKE – F# Make"-article.

Although the new release contains many bugfixes, I only want to show the two major improvements here.

1. FAKE 0.10 uses FSI instead of FSC

From now on FAKE uses the “F# Interactive” (fsi.exe) instead of the F# Compiler (fsc.exe) to run the build scripts, which brings two major improvements.

No TempPath for compiled binaries needed

Due to the fact that FAKE scripts are no longer compiled at the beginning of the build process, we don’t need a temporary folder for the created binaries.

Loading modules at runtime

The #load command in F# scripts allows us to load modules at runtime. Now we are able to put reusable Targets or TargetTemplates (see below) into external build script files.

2. TargetTemplates

TargetTemplates provide an easy way to reuse common Targets. Let’s consider a (very) small sample:

This Target “TraceHello” traces a “Hello World” string into our build log. Now we want it to be slightly more generic and to trace a custom string. We can do this by using a TargetTemplate:

Now we have a template (or a function which generates targets) that gets a string for the target name and a string for the trace text and generates  a usable target:

Of course the TargetTemplate function is generic and can be used with any tuple as parameter:

Yesterday I was talking about F# at the .NET Developer Group Braunschweig. It was my first talk completely without PowerPoint (just Live-Coding and FlipChart) and I have to admit this is not that easy. But the event was really a big fun and we covered a lot of topics like FP fundamentals, concurrency and domain specific languages (of course I showed “FAKE – F# Make”).

Now I have a bit time before I go to the next BootCamp in Leipzig. Today Christian Weyer will show us exciting new stuff about WCF and Azure.

In the meanwhile I will write here about another important question (see first article) from the F# BootCamp in Leipzig:

Question 4 – Try to explain “Currying” and “Partial Application”. Hint: Please show a sample and use the pipe operator |>.

Obviously this was a tricky question for FP beginners. There are a lot of websites, which give a formal mathematical definition but don’t show the practical application.

“Currying … is the technique of transforming a function that takes multiple arguments (or more accurately an n-tuple as argument) in such a way that it can be called as a chain of functions each with a single argument”

[Wikipedia]

I want to show how my pragmatic view of the terms here, so let’s consider this small C# function:

public int Add(int x, int y)
{
   return x + y;
}

Of course the corresponding F# version looks nearly the same:

let add(x,y) = x + y

But let’s look at the signature: val add : int * int –> int. The F# compiler is telling us add wants a tuple of ints and returns an int. We could rewrite the function with one blank to understand this better:

let add (x,y) = x + y

As you can see the add function actually needs only one argument – a tuple:

let t = (3,4)         // val t : int * int
printfn "%d" (add t)  // prints 7 – like add(3,4)

Now we want to curry this function. If you’d ask a mathematician this a complex operation, but from a pragmatic view it couldn’t be easier. Just remove the brackets and the comma – that’s all:

let add x y = x + y

Now the signature looks different: val add : int -> int –> int

But what’s the meaning of this new arrow? Basically we can say if we give one int parameter to our add function we will get a function back that will take only one int parameter and returns an int.

let increment = add 1      // val increment : (int -> int)
printfn "%d" (increment 2) // prints 3

Here “increment” is a new function that uses partial application of the curryied add function. This means we are fixing one of the parameters of add to get a new function with one parameter less.

But why are doing something like this? Wouldn’t it be enough to use the following increment function?

let add(x,y) = x + y       // val add : int * int -> int 
let increment x = add(x,1) // val increment : int -> int
printfn "%d" (increment 2) // prints 3

Of course we are getting (nearly) the same signature for increment. But the difference is that we can not use the forward pipe operator |> here. The pipe operator will help us to express things in the way we are thinking about it.

Let’s say we want to filter all even elements in a list, then calculate the sum and finally square this sum and print it to the console. The C# code would look like this:

var list = new List<int> {4,2,6,5,9,3,8,1,3,0};
Console.WriteLine(Square(CalculateSum(FilterEven(list))));

If we don’t want to store intermediate results we have to write our algorithm in reverse order and with heavily use of brackets. The function we want to apply last has to be written first. This is not the way we think about it.

With the help of curried functions, partial application and the pipe operator we can write the same thing in F#:

let list = [4; 2; 6; 5; 9; 3; 8; 1; 3; 0]

let square x = x * x

list
 |> List.filter (fun x -> x % 2 = 0) // partial application
 |> List.sum
 |> square
 |> printfn "%A"                     // partial application

We describe the data flow in exactly the same order we talked about it. Basically the pipe operator take the result of a function and puts it as the last parameter into the next function.

What should we learn from this sample?

1. Currying has nothing to do with spicy chicken.
2. The |> operator makes life easier and code better to understand.
3. If we want to use |> we need curryied functions.
4. Defining curryied functions is easy – just remove brackets and comma.
5. We don’t need the complete mathematical theory to use currying.
6. Be careful with the order of the parameter in a curryied function. Don’t forget the pipe operator puts the parameter from the right hand side into your function – all other parameters have to be fixed with partial application.

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