Wednesday, July 28, 2010

An F# Silverlight MVVM Multi-Project Template

In the spirit of continuing to build up set of project templates for F#, I've created an F# Silverlight MVVM multi-project template.

Here are the links to the other templates that have been announced on this blog:

- WPF MVVM Multi-Project  Template: A Polyglot Approach
- An F# WPF MVVM Project Template
- Standard WCF Template 
- Standard ASP.NET MVC 2 Template

The code provided by this multi-project template creates an application that is very similar to the output of the previously metioned F# WPF templates.

It looks something like this:

The following list shows the high level code changes that were needed to port the polyglot WPF template to Silverlight:

- Created new projects from the default C# and F# Silverlight 4 project templates.
- Made several revisions related to XAML resources.
- Changed the DataGrid control and Label controls to the Silverlight versions.

You can download the template here and find the full source at

Sunday, July 25, 2010

The Mars Rovers Challenge

The Mars Rovers Challenge is a simple software development exercise.

The details are as follows:

A squad of robotic rovers are to be landed by NASA on a plateau on Mars.
This plateau, which is curiously rectangular, must be navigated by the
rovers so that their on-board cameras can get a complete view of the
surrounding terrain to send back to Earth.

A rover's position and location is represented by a combination of x and y
co-ordinates and a letter representing one of the four cardinal compass
points. The plateau is divided up into a grid to simplify navigation. An
example position might be 0, 0, N, which means the rover is in the bottom
left corner and facing North.

In order to control a rover, NASA sends a simple string of letters. The
possible letters are 'L', 'R' and 'M'. 'L' and 'R' makes the rover spin 90
degrees left or right respectively, without moving from its current spot.
'M' means move forward one grid point, and maintain the same heading.

Assume that the square directly North from (x, y) is (x, y+1).

The first line of input is the upper-right coordinates of the plateau, the
lower-left coordinates are assumed to be 0,0.

The rest of the input is information pertaining to the rovers that have
been deployed. Each rover has two lines of input. The first line gives the
rover's position, and the second line is a series of instructions telling
the rover how to explore the plateau.

The position is made up of two integers and a letter separated by spaces,
corresponding to the x and y co-ordinates and the rover's orientation.

Each rover will be finished sequentially, which means that the second rover
won't start to move until the first one has finished moving.

The output for each rover should be its final co-ordinates and heading.


Test Input:
5 5
1 2 N
3 3 E

Expected Output:
1 3 N
5 1 E

The solution that I have put together is admittedly way over-engineered and it doesn't cover every scenario (i.e. tracking of rovers, rover collisions, etc.).  However, it does satisfy the requirements defined above (and then some).  Additionally, it shows object-oriented design, DRY (Don't Repeat Yourself), application of many of the SOLID principles, and application of several design patterns (i.e. Command, Specification, Template, etc).

You can find the full solution at

Tuesday, July 20, 2010

Nashville Geek Lunch 11:30 AM Next Tuesday (7/27/2010)

It's time for another Nashville Geek Lunch. Head out to Qdoba in Brentwood, TN next Tuesday (7/27/2010) from 11:30 - 12:30 for good food and great conversation with some of Nashville's finest developers and technologists.  There is no set discussion topic; however, you'll undoubtedly hear a little about .NET 4, F#, jQuery, ASP.NET MVC, Ruby, and more.  Additional information can be found at

I hope to see you there!

Monday, July 5, 2010

Presentation: 5 Best Practices for F# Development - Slides and Examples

Thanks to all who come out to the New England F# User Group meeting tonight!

Based on an excellent recommendation from Elijah Manor, I have embedded the slide deck in this post:
The slides and examples can also be found at