I finished the Pluralsight course finally. I’m still studying F# 2 pomodoros a day but lately lost he motivation to publish the notes. In this post I’ll tidy up the notes. In order to maintain my cadence I think I had better develop more stuff instead of covering theoretical subjects.

More Notes

• Upcasting / Downcasting To upcast :> operator is used. Alternatively the keyword upcast can be used to achieve the same results. It performs a static cast and the cast is determined at runtime.

Downcasting is performed by the :?> operator or downcast keyword.

• Abstract classes Abstract classes are decorated with **[]**. To mark members **abstract** keyword is used:

abstract Area : float with get
abstract Perimeter : float  with get
abstract Name : string with get

• obj is shortcut for System.Object
• do bindings perform actions when the object is constructed. do bindings are usually put after let bindings so that code in the do binding can execute with a fully initialized object.
• unit is equivalent of void
• tabs are not allowed as they can indicate an unknown number of space characters and as spaces and indents matter
• ‘a means generic. By default a function f is infered as ‘a -> bool meaning it takes a general parameter and returns boolean

• Providing an incomplete list of functions result in a new function (currying)
• Getting values from tuples: fst gets the first value, snd gets the second value
• You can attach elements to a list by using the :: (cons) operator
• @ operator Concatenates two lists.
• Exceptions can be thrown using raise function. Reraise function rethrows an exception
• BigInt (C# and VB) don’t have support for arbitrarily long integers

Resources

• Book: Programming F# 3.0
• Pluralsight course: Introduction to F#
• MSDN Article: Casting and Conversions
• MSDN Article: Abstract Classes
• MSDN Article: do Bindings in Classes

Going over the F# Pluralsight course I learned a few more things and thought I should use them to improve my world-famous Rock-Paper-Too-Long-To-Type game.

New tidbits and improvements in the game

• new keyword is only required when the type implements IDisposable. So no need to use them on my RPSLS object. It works exactly the same.

• default constructor can be defined such as

new() = Car("red", 3)

• You can access the constructor parameters anywhere in the object so there is no need to assign it to another value.

• Assigning values to enum values makes it compatible with other.NET languages. When I assigned values to moves an interesting thing happened. I stated getting this error: Enumerations cannot have members So you can overload operators in a discriminated union in F# and you can use it in F# only but if you want your type be compatible with other CLR languages than you can only use it as a regular enum.

After I assigned the values my Move discriminated union became:

type Move = 
    | Rock = 0
    | Spock = 1
    | Paper = 2
    | Lizard = 3
    | Scissors = 4

So no more overloaded minus operator which significantly reduced the lines of code in the type. After Googling a bit I found out that generally the above values are assigned to moves the winner is determined by extracting computer number from the player number and applying modulo operator. For example: When player plays rock (0) and computer plays paper (2)

difference = player - computer = 0 - 2 = -2
result = -2 % 5 = 3 --> Python returns 3 after this operation

if result < 3 then player wins
if result >= 3 then computer wins 

Apparently in F#, -2 % 5 = -2! So I had to add 5 before applying modulo operator:

let diff = ((int)(this.PlayerMoves.Item(i) - ComputerMoves.Item(i)) + 5) % 5

Conclusion

I’m still working with the PluralSight course. In the next post I’ll examine type casting, abstract types and do bindings etc

Resources

• Python implementation of RPSLS game
• Pluralsight course: Introduction to F#

My problem is I have a ton of gadgets and keep getting more before building meaningful projects with the previous ones. So I decided to be a good boy and create at least one full project with the existing ones before I move on to new shiny toys. First target is my .NET Gadgeteer hardware kit set that’s been lying around for a quite some time. For the sake of completeness here are the previous posts about Gadgeteer so far:

• Cleaning up .NET Gadgeteer work environment
• Playing with .NET Gadgeteer

My main goal now is to discover the capabilities of the kit I have and try to come up with a fun project. So as I have no clue at the moment I will play around with each component I have and create sample projects for each them. By the end I hope I’ll get a nice idea.

What is it anyway?

The official definiton is: “Microsoft .NET Gadgeteer is an open-source toolkit for building small electronic devices using the .NET Micro Framework” I think it’s a great kit for children because it makes development a lot easier than say Arduino.

All sockets are labelled and all you have to do is connect the mathcing sockets in the module and mainboard:

Also if you are a .NET developer there is absolutely no learning curve. You just build your application just like you’ve been building all along.

Setting up the development environment!

Well, there is no learning curve but still you need to make some preparations. First thing you need to do is install the .NET Micro Framework. Then the next step I took is install the Gadgeteer project templates for Visual Studio 2013. All of these can be found at the downloads section at GHI Electronics website.

Once you install the Gadgeteer package you should be able to create new Gadgeteer projects when you select File -> New Project in Visual Studio:

Next step is to select the mainboard you’re going to use in the project:

First rule of gadget development: Fork over the money!

Once you install the required software you will of course need the actually hardware to run your applications on. The bulk of modules I currently have came from the starter kit I initially bought:

Then I added a few more components but there are so many more that can be purchased. Since it’s an open hardware platform any vendor can build their own modules. But looks like, even though it’s open-source, a company called GHI Electronics are taking the lead in this market.

Let’s get down to business!

I will explain each module in depth in the upcoming posts but for the purposes of testing the development environment I’ll just build a sample project consisting of Spider mainboard and 3 LEDs.

First component I’m going to play around is multi color LED. I happen to have 3 of them and added all of them to my design. Once you drag and drop the modules you want to use in your project you can simply right-click on an empty point on the canvas and select Connect All Modules. It automatically connects using the appropriate slots for each module. So you can instantly get something like this:

And the source code I’m going to use to test it is as follows:

public partial class Program
{
	void ProgramStarted()
	{
		multicolorLED.TurnOff();
		multicolorLED2.TurnOff();
		multicolorLED3.TurnOff();

		multicolorLED.TurnBlue();
		multicolorLED2.TurnGreen();
		multicolorLED3.TurnRed();
	}
}

Once you get such a visual design it’s very easy to build the actual hardware by referring to this:

By the way, I’m using Tamiya universal plate to keep modules nice and tidy otherwise they hang around uncontrollably. So it is quite handy.

Conclusion

I’ll leave it here. I’m hoping this post should have enough information for anyone who wants to start developing projects with .NET Gadgeteer hardware kit. In the next post I’ll go over each component and discover their capabilities. If you already have a Gadgeteer kit your mileage may vary as I can only cover the devices I own. I’d appreciate if you submit any project ideas. I can acquire the modules needed and add to my projects.

Resources

• Official Gadgeteer site
• GHI Downloads
• Tamiya universal plate