The Hogg Blog : C#

Creating a Logo / Turtle Graphics Textual DSL using Oslo MGrammar

Jason Hogg — Wed, 26 Nov 2008 01:17:00 GMT

In the early 1980's a programming language called Turtle Graphics was used as a means of introducing novices to programming on the BBC Microcomputer. Turtle graphics, a graphical version of Logo, helped introduce people to programming using a simple functional language that provided instant visual gratification allowing the user to move a triangular turtle across the screen using simple commands such as forward, backward, right turn and left turn.

At PDC this year the Connected Systems team introduced a new language called "M" - which allows textual DSL's to be created. I will talk more about this language in future posts especially compared with the F# Lexer and Parser that we used to create our textual DSL for SecPAL, but first I wanted to create a programming language with which to learn Mg. I thought a version of Turtle Graphics would be fun - and interesting for anyone else interested in experimenting with or learning Mg.

The programming language I am liberally calling Logo (and the associated interpreter) are fairly simple - but I thought it would be fun for people to play with, especially those with children who are looking for new ways to introduce their kids to progamming. I did the bulk of the work specifying the grammar for this simple version of Logo on the flight back from LA to Seattle - which should give you a sense of how intuitive Mg is - and how productive the Intellipad authoring experience is.

Given that Thanksgiving is just two days away I figured it would be patriotic (odd coming from an Aussie/Kiwi/Pom hybrid) to show how simple it is for this language to draw the United States flag - a design which obviously would make significant use of loops and nested loops.

The screenshot above shows the output from this program. The complete logo program listing is also included below so you can see how complex objects can be created using a simple grammar comprising of just 5 commands:

    - Commands - Commands perform actions such as moving or rotating.
        Rotate n - Rotate 'n' degrees
        Draw n - Draw a line 'n' pixels long
        MoveAbs x, y - Move to an absolute position
        Move x,y - Move to a position relative to last move / draw command
    - Loops - Sets of instructions which are executde iteratively. Loops can be nested.
        Loop n { [Command] }*

I have attached the full source code for this so that you can play with this yourself. The source code is based on the PDC (October?) version of Oslo which you will have to first download from MSDN. The language could easily be extended to include color, line widths, other types of lines such as bezier curves etc - which should provide a good introduction for anyone interested. Post pointers if you do anything fun with this.

In addition to the formal grammar for my logo language (logo.mg) the .zip file also includes a WPF interpreter that interprets the parsed output of our logo programs and converts them into WPF Path Geometry syntax. There is also a simple editor that allows you to edit and run our Logo programs - providing a nice easy way to start teaching your children to program. Or for yourself to start modifying the language as described above.

Enjoy!!! And (to those in America) Happy Thanksgiving...

// Logo (and Mg) sample program
// Happy Thanksgiving!

// Move to top left
MoveAbs 25,25

// Draw five rows of stars
Loop 5
{
   // Draw ten columns of stars
   Loop 10
   {
   // Draw five points to make each star
   Loop 5
   {
         Rotate -54
         Draw 5
         Rotate 126
         Draw 5
   }
   Move 20 -1
   }
   Move -210,20
}

// Draw the lines next to the stars
MoveAbs 430,25
Rotate -90
Loop 5
{
   // Lines are 5 pixels high
   Loop 5
   {
      Draw 200
      Move 200,1
   }
   Move 0 15
}

// Draw the lower lines on the flag
MoveAbs 430,125
Loop 5
{
   // Lines are 5 pixels high
   Loop 5
   {
      Draw 410
      Move 410,1
   }
   Move 0,15
}

patterns & practices Improving Web Services Security: Now Available!

Jason Hogg — Fri, 20 Jun 2008 17:51:00 GMT

Over the last 12 months we have had a lot of people who used the Web Service Security - Scenarios, Patterns and Implementation Guidance ask us where the implementation guidance for WCF was. Great news. JD Meier, Jason Taylor, Prashant Bansode and Rob Boucher and the rest of his P&P team have just released their guide which includes Security Fundamentals for Web Services, WCF Security Fundamentals and Scenario specific guidance. Great stuff - and a must read for anyone designing secure distributed systems based on WCF. Available from: http://www.codeplex.com/WCFSecurityGuide

WhoIs Shenanigans

Jason Hogg — Tue, 01 Apr 2008 03:29:00 GMT

I am sure that everyone has used a WhoIs utility (such as http://www.internic.org/whois.html) for querying the owner of a domain name such as microsoft.com. There is however an alternative to these Web forms which provides more information allowing you to search not just for strings matching a domain name, but also for strings matching registered hostnames of domain names. This provides hysterical insight into the minds of some Webmasters. For a laugh take a look at some of these hostnames registered with microsoft.com or google.com in them.

MICROSOFT.COM.WILL.LIVE.FOREVER.BECOUSE.UNIXSUCKS.COM
MICROSOFT.COM.WILL.BE.BEATEN.WITH.MY.SPANNER.NET
MICROSOFT.COM.SOFTWARE.IS.NOT.USED.AT.REG.RU
MICROSOFT.COM.SHOULD.GIVE.UP.BECAUSE.LINUXISGOD.COM
MICROSOFT.COM.IS.NOT.HOSTED.BY.ACTIVEDOMAINDNS.NET
MICROSOFT.COM.IS.GOD.BECOUSE.UNIXSUCKS.COM
MICROSOFT.COM.HAS.ITS.OWN.CRACKLAB.COM
MICROSOFT.COM

GOOGLE.COM.ZOMBIED.AND.HACKED.BY.WWW.WEB-HACK.COM
GOOGLE.COM.YAHOO.COM.MYSPACE.COM.YOUTUBE.COM.FACEBOOK.COM.THEYSUCK.DNSABOUT.COM
GOOGLE.COM.IS.NOT.HOSTED.BY.ACTIVEDOMAINDNS.NET
GOOGLE.COM.IS.HOSTED.ON.PROFITHOSTING.NET
GOOGLE.COM.ACQUIRED.BY.CALITEC.NET
GOOGLE.COM

To see the complete list (r rated) try running the code yourself. Post a response with your funniest hostname or domain names other than these two that are particularly funny.

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Net.Sockets;

using System.IO;

namespace WhoIsQuery

{

class Program

{

static void Main(string[] args)

{

// A query that results in more than one result lists all possible results

// so that a more precise query can be entered.

// A query with only one result returns just that result.

// Send request to WhoIs Server

Console.WriteLine("Contacting Internic");

TcpClient client = new TcpClient("whois.internic.net", 43);

StreamWriter writer = new StreamWriter(client.GetStream());

writer.WriteLine("microsoft.com");

writer.Flush();

// Retrieve response

StringBuilder output = new StringBuilder();

StreamReader reader = new StreamReader(client.GetStream());

{

output.Append(reader.ReadLine() + Environment.NewLine);

}

while (!reader.EndOfStream);

Console.WriteLine(output);

Console.ReadLine();

}