Matt Manela's Blog

Snippet Designer 1.2 Beta Release with Visual Studio 2010 Support

MattManela — Fri, 22 Jan 2010 14:52:00 GMT

Yesterday I released Snippet Designer 1.2 Beta.

Codeplex Page: http://snippetdesigner.codeplex.com/

Visual Studio Gallery Page: http://visualstudiogallery.msdn.microsoft.com/en-us/B08B0375-139E-41D7-AF9B-FAEE50F68392

This release contains several bug fixes but more importantly it now includes support for Visual Studio 2010.

I am super excited for this since now you can install the Snippet Designer from inside of Visual Studio using the new extension manager. Just open up the extension manager and search for “Snippet Designer”.

Then you just need to install it and restart Visual Studio.

Enjoy!

Regex based Lexer with F#

MattManela — Tue, 19 Jan 2010 14:52:00 GMT

This lexer allows you to define your regular expression based rules in a very declarative way using F# computation expressions.

open Lexer
let definitions = 
    lexerDefinitions {
        do! addNextlineDefinition "NEWLINE" @"(\n\r)|\n|\r"
        do! addIgnoreDefinition "WS"        @"\s"
        do! addDefinition "LET"             "let"
        do! addDefinition "ID"              "(?i)[a-z][a-z0-9]*"
        do! addDefinition "FLOAT"           @"[0-9]+\.[0-9]+"
        do! addDefinition "INT"             "[0-9]+"
        do! addDefinition "OPERATOR"      @"[+*=!/&|<>\^\-]+"   
    }

With those defined you can execute the lexer with:

open Lexer
let lex input = 
    try    
        let y = Lexer.tokenize definitions input
        printfn "%A" y
    with e -> printf "%s" e.Message
lex "let a = 5"

Which will result in:

seq [{name = "LET";
      text = "let";
      pos = 0;
      column = 0;
      line = 0;}; {name = "ID";
                   text = "a";
                   pos = 4;
                   column = 4;
                   line = 0;}; {name = "OPERATOR";
                                text = "=";
                                pos = 6;
                                column = 6;
                                line = 0;}; {name = "INT";
                                             text = "5";
                                             pos = 8;
                                             column = 8;
                                             line = 0;}]

The lexer’s code is structured in three parts. The first part is a state monad using the F# computation expressions. This enables the declarative approach (seen above) to setup your lexer rules.

module StateMonad
type State<'s,'a> = State of ('s -> ('a *'s))
let runState (State f) = f
type StateBuilder() = 
    member b.Return(x) = State (fun s -> (x,s))
    member b.Delay(f) = f() : State<'s,'a>
    member b.Zero() = State (fun s -> ((),s))
    member b.Bind(State p,rest) = State (fun s -> let v,s2 = p s in  (runState (rest v)) s2)
    member b.Get () = State (fun s -> (s,s))
    member b.Put s = State (fun _ -> ((),s))

The second part are the combinators that are used to define your lexer rules. There are three main combinators: AddDefinition which lets you define a name / regex pair, AddIgnoreDefinition which lets you define characters which the lexer should ignore and AddNextlineDefinition which lets you define what characters determine a new line.

type LexDefinitions = 
  {regexes : string list;
   names : string list;
   nextlines : bool list;
   ignores : bool list; }
   
let buildDefinition name pattern nextLine ignore =
    state {
        let! x = state.Get()
        do! state.Put { regexes = x.regexes @  [sprintf @"(?<%s>%s)" name pattern];
                        names = x.names @ [name]; 
                        nextlines  = x.nextlines @ [nextLine];
                        ignores = x.ignores @ [ignore]}
    }
    
let addDefinition name pattern = buildDefinition name pattern false false
let addIgnoreDefinition name pattern = buildDefinition name pattern false true
let addNextlineDefinition name pattern = buildDefinition name pattern true true

And the final part is the code that performs the tokenizing. It uses the Seq.unfold method to create the list of tokens. Unfold is a function which takes a single item and generates a list of new items from it. It is the opposite of Seq.fold which takes a list of items and turns it into a single item. The tokenize function used Seq.unfold to generate each token while keeping track of the current line number, position in that line and position in the input string.

type Token = 
    { name : string;
      text: string; 
      pos :int;
      column: int;
      line: int }
   
let createLexDefs pb =  (runState pb) {regexes = []; names = []; nextlines = []; ignores = []} |> snd
 
let tokenize lexerBuilder (str:string) = 
    let patterns = createLexDefs lexerBuilder
    let combinedRegex =  Regex(List.fold (fun acc reg -> acc + "|" + reg) (List.head patterns.regexes) (List.tail patterns.regexes))
    let nextlineMap = List.zip patterns.names patterns.nextlines |> Map.ofList
    let ignoreMap = List.zip patterns.names patterns.ignores |> Map.ofList
    let tokenizeStep (pos,line,lineStart) = 
        if pos >= str.Length then
            None
        else
            let getMatchedGroupName (grps:GroupCollection) names = List.find (fun (name:string) -> grps.[name].Length > 0) names
            match combinedRegex.Match(str, pos) with
                | mt when mt.Success && pos = mt.Index  -> 
                    let groupName = getMatchedGroupName mt.Groups patterns.names
                    let column = mt.Index - lineStart
                    let nextPos = pos + mt.Length
                    let (nextLine, nextLineStart) = if nextlineMap.Item groupName then (line + 1, nextPos) else (line,lineStart)
                    let token = if ignoreMap.Item groupName 
                                then None 
                                else Some {
                                        name = groupName; 
                                        text = mt.Value; 
                                        pos = pos; 
                                        line = line; 
                                        column = column; }
                    Some(token, (nextPos, nextLine, nextLineStart))
                    
                | otherwise -> 
                    let textAroundError = str.Substring(pos, min (pos + 5) str.Length)
                    raise (ArgumentException (sprintf "Lexing error occured at line:%d and column:%d near the text:%s" line (pos - lineStart) textAroundError))
    Seq.unfold tokenizeStep (0, 0, 0) |> Seq.filter (fun x -> x.IsSome) |> Seq.map (fun x -> x.Value)

Lastly, here are the unit tests written using XUnit.Net:

module LexerFacts
open Xunit
open Lexer
open System.Linq
let simpleDefs = 
    state {
        do! addNextlineDefinition "NextLine"           "/"
        do! addIgnoreDefinition "IgnoredSymbol"        "=+"
        do! addDefinition "String"                     "[a-zA-Z]+"
        do! addDefinition "Number"                     "\d+"
        do! addDefinition "Name"                       "Matt"
    }
[<Fact>]
let Will_return_no_tokens_for_empty_string() =
  
    let tokens = Lexer.tokenize simpleDefs ""
    
    Assert.Equal(0, tokens.Count())
[<Fact>]
let Will_throw_exception_for_invalid_token() =
  
    let tokens = Lexer.tokenize simpleDefs "-"
    let ex = Assert.ThrowsDelegateWithReturn(fun () -> upcast tokens.Count()) |> Record.Exception
    Assert.NotNull(ex)
    Assert.True(ex :? System.ArgumentException)
[<Fact>]
let Will_ignore_symbols_defined_as_ignore_symbols() =
  
    let tokens = Lexer.tokenize simpleDefs "========="
    
    Assert.Equal(0, tokens.Count())
[<Fact>]
let Will_get_token_with_correct_position_and_type() =
  
    let tokens = Lexer.tokenize simpleDefs "1one=2=two"
    
    Assert.Equal("Number",tokens.ElementAt(2).name)
    Assert.Equal("2",tokens.ElementAt(2).text)
    Assert.Equal(5,tokens.ElementAt(2).pos)
    Assert.Equal(5,tokens.ElementAt(2).column)
    Assert.Equal(0,tokens.ElementAt(2).line)
[<Fact>]
let Will_tokenize_string_with_alernating_numbers_and_strings() =
  
    let tokens = Lexer.tokenize simpleDefs "1one2two"
    
    Assert.Equal("1",tokens.ElementAt(0).text)
    Assert.Equal("one",tokens.ElementAt(1).text)
    Assert.Equal("2",tokens.ElementAt(2).text)
    Assert.Equal("two",tokens.ElementAt(3).text)
[<Fact>]
let Will_increment_line_with_newline_symbol() =
  
    let tokens = Lexer.tokenize simpleDefs "1one/2two"
    
    Assert.Equal("Number",tokens.ElementAt(2).name)
    Assert.Equal("2",tokens.ElementAt(2).text)
    Assert.Equal(5,tokens.ElementAt(2).pos)
    Assert.Equal(0,tokens.ElementAt(2).column)
    Assert.Equal(1,tokens.ElementAt(2).line)
[<Fact>]
let Will_give_priority_to_lexer_definitions_defined_earlier() =
  
    let tokens = Lexer.tokenize simpleDefs "Matt"
    
    Assert.Equal("String",tokens.ElementAt(0).name)

I attached a zip (Lexer.zip) containing all the code mentioned above.

Count the number of lines in your project with one line of Powershell

MattManela — Fri, 11 Dec 2009 14:50:00 GMT

ls * -recurse -include *.aspx, *.ascx, *.cs, *.ps1 | Get-Content | Measure-Object -Line

Just replace the file extensions with the ones you use in your project.

Useful Moq Extension Method

MattManela — Wed, 25 Nov 2009 00:03:00 GMT

I have been working with ASP .NET MVC and I use the Moq mocking library to help test the code I write. Often in ASP MVC anonymous objects are passed around as function arguments. This is especially common in calls to RouteUrl. Since I want to be able to test this and verify that it is called correctly I wrote a handy extension method to make it easier called AsMatch.

To be able to test the UrlHelper (since it doesn't have an interface or virtual methods) I wrote a simple wrapper around it with an interface to enable testing. Using that with this extension method makes testing route generation a breeze.

Given a call to generate a Url like this:

var url = Url.RouteUrl("Show", new { projectName="matt" });

You can write a setup on your Mock of the Url helper using a similar syntax:

UrlHelperMock
.Setup(x => x.RouteUrl("Show",new{ projectName="matt"}.AsMatch()))
.Return("someUrlToTest");

Here is the code that defines the AsMatch extension method:

    public static class ObjectMoqExtensions
    {
        public static object AsMatch(this object @object)
        {
            return Match<object>.Create(testObject => DoObjectsMatch(@object, testObject));
        }
        private static bool DoObjectsMatch(object object1, object object2)
        {
            var props1 = ToDictionary(object1);
            var props2 = ToDictionary(object2);
            var query = from prop1 in props1
                        join prop2 in props2 on prop1.Key equals prop2.Key
                        select prop1.Value.Equals(prop2.Value);
            return query.Count(x => x) == Math.Max(props1.Count(), props2.Count());
        }
        public static Dictionary<string, object> ToDictionary(object @object)
        {
            var dictionary = new Dictionary<string, object>();
            var properties = TypeDescriptor.GetProperties(@object);
            foreach (PropertyDescriptor property in properties)
                dictionary.Add(property.Name, property.GetValue(@object));
            return dictionary;
        }
    }

Converting RTF to HTML

MattManela — Mon, 28 Sep 2009 21:28:00 GMT

Have you ever had the desire to convert some RTF text into HTML? Probably not. But if you do, then you are in luck! I recently had the need to do this conversion and after some searching found out a way to do it by enhancing a sample distributed in the MSDN library. The sample is called: XAML to HTML Conversion Demo.

The sample has code which converts HTML to and from a XAML Flow Document. But this doesn’t make things easier until you realize that there is a way to convert RTF to XAML easily. The key is to use System.Windows.Controls.RichTextBox which can load RTF from a stream and save it as XAML. This conversion is shown below:

        private static string ConvertRtfToXaml(string rtfText)
        {
            var richTextBox = new RichTextBox();
            if (string.IsNullOrEmpty(rtfText)) return "";
            var textRange = new TextRange(richTextBox.Document.ContentStart, richTextBox.Document.ContentEnd);
            using (var rtfMemoryStream = new MemoryStream())
            {
                using (var rtfStreamWriter = new StreamWriter(rtfMemoryStream))
                {
                    rtfStreamWriter.Write(rtfText);
                    rtfStreamWriter.Flush();
                    rtfMemoryStream.Seek(0, SeekOrigin.Begin);
                    textRange.Load(rtfMemoryStream, DataFormats.Rtf);
                }
            }
            using (var rtfMemoryStream = new MemoryStream())
            {
                textRange = new TextRange(richTextBox.Document.ContentStart, richTextBox.Document.ContentEnd);
                textRange.Save(rtfMemoryStream, DataFormats.Xaml);
                rtfMemoryStream.Seek(0, SeekOrigin.Begin);
                using (var rtfStreamReader = new StreamReader(rtfMemoryStream))
                {
                    return rtfStreamReader.ReadToEnd();
                }
            }
        }

With this code we have all we need to convert RTF to HTML. I modified the sample to add this RTF To XAML conversation and then I run that XAML through HTML converter which results in the HTML text. I added an interface to these conversion utilities and converted the sample into a library so that I would be able to use it from other projects. Here is the interface:

 public interface IMarkupConverter
    {
        string ConvertXamlToHtml(string xamlText);
        string ConvertHtmlToXaml(string htmlText);
        string ConvertRtfToHtml(string rtfText);
    }
    public class MarkupConverter : IMarkupConverter
    {
        public string ConvertXamlToHtml(string xamlText)
        {
            return HtmlFromXamlConverter.ConvertXamlToHtml(xamlText, false);
        }
        public string ConvertHtmlToXaml(string htmlText)
        {
            return HtmlToXamlConverter.ConvertHtmlToXaml(htmlText, true);
        }
        public string ConvertRtfToHtml(string rtfText)
        {
            return RtfToHtmlConverter.ConvertRtfToHtml(rtfText);
        }
    }

With this I am now able to convert from RTF to HTML. However, there is one catch - the conversion uses the RichTextBox WPF control which requires a single threaded apartment (STA). Therefore in order to run your code that calls the ConvertRtfToHtml function, it must also be running in a STA. If you can’t have your program run in a STA then you must create a new STA thread to run the conversion. Like this:

MarkupConverter markupConverter = new MarkupConverter();
private string ConvertRtfToHtml(string rtfText)
{
   var thread = new Thread(ConvertRtfInSTAThread);
   var threadData = new ConvertRtfThreadData { RtfText = rtfText };
   thread.SetApartmentState(ApartmentState.STA);
   thread.Start(threadData);
   thread.Join();
   return threadData.HtmlText;
}
private void ConvertRtfInSTAThread(object rtf)
{
   var threadData = rtf as ConvertRtfThreadData;
   threadData.HtmlText = markupConverter.ConvertRtfToHtml(threadData.RtfText);
}
        
private class ConvertRtfThreadData
{
   public string RtfText { get; set; }
   public string HtmlText { get; set; }
}

Here is the zip contain the code for the Markup converter: MarkupConverter.zip

I finally got fed up with Enum.Parse

MattManela — Fri, 24 Jul 2009 19:02:04 GMT

I don’t know why I didn’t do this long ago, but I am done writing this:

var val = (SomeEnum)Enum.Parse(typeof(SomeEnum),”someString”);

I have typed this too many times and it annoys me.

I wrote a small extension method on the string type to make this better:

public static class StringExtensions
{
    public static T ToEnum<T>(this string @string)
    {
        return (T)Enum.Parse(typeof (T), @string);
    }
}

With this I can now write the previous line as:

var val = "someString".ToEnum<SomeEnum>()

It is a bit shorter and I think much more readable.

DRY and Unit Tests don’t mix well

MattManela — Mon, 13 Jul 2009 06:08:50 GMT

When reading source code, I sometimes come across unappealing code(sometimes even my own). However, there is one kind of “bad code” I see quite frequently. It is a set of unit tests which have had the DRY (Don't Repeat Yourself) principle unduly forced upon them. DRY is the idea that you shouldn’t have to write the same code over and over; abstract it in a function or a class and just call the abstraction. This is all well and good in most cases, but I find it misguided when applied to a test case.

A test case should be like a simple short story. The characters are introduced, action/conflict occurs and then resolution takes place (sometimes with a moral). This (kind of) corresponds to the 3 steps of a unit test: arrange, act and assert. You arrange and setup what you need for your test to run, you perform the action that you are trying to test and then you assert the results. The issue I find is that a coder, in attempting to apply DRY to his test cases, will abstract away all of the arrange step into a function often with a name like SetupExpectations or just Setup. This goes against the point of a test case. A test case needs to be concise and tell me everything I need to know about how that one bit of functionality works. I don’t want to jump around the test class trying to read one test case. To me, this is like reading a book that says, “If you want to learn about the characters in this book please open this other book.” This doesn’t stop you from understanding the test, but it slows you down…and is just annoying.

That is why I will come out and say do not apply DRY haphazardly to test cases.

How to teach your girlfriend Hexadecimal?

MattManela — Wed, 06 May 2009 23:49:00 GMT

It is an age old question: How do you teach your girlfriend hex?

I encountered this problem when I was a web developer in college for a late night student activities program aptly named Late Nite Binghamton. My co-worker and girlfriend Mallory was a graduate assistant for the program and had many ideas for how to make the website better and more engaging. While working with her she would often see me typing in the hexadecimal color codes in css such as:

color: #F24A7D

As I am inept with what color look good (I often say that I never learnt colors) I would often ask her for help with picking out colors and I decided that if she was able to give me these colors in their hex color codes it would make us more efficient :) I sat her down and described to her how they work but after talking for a bit I realized that although she understood everything that I said she wouldn’t gain a feel for what hex numbers related to what colors just from hearing me talk.

In order to help her gain this feel I created a simple game called The Mallory Color Guessing Game. The game is a webpage which shows you a large colored box and it is your job to guess what the hex color code is.

After you guess it tells you how close you were to the actual color:

This game was a hit! Mallory loved it and she would compete with me to see who could guess the color the best. Pretty quickly she gained a feel for what the hex digits meant and what color they represented. And that is how I taught my girlfriend hex!

NOTE: Mallory consistently gets over 80% at the Mallory Color Guessing Game.

Snippet Designer in April’s MSDN Magazine!

MattManela — Wed, 15 Apr 2009 02:33:47 GMT

I am excited to announce that the Snippet Designer is featured in the April issue of MSDN Magazine.

It is featured in the Toolbox column where they highlight useful tools and blogs. Here is a snippet of what it says:

Creating Code Snippets is a lot easier when using Snippet Designer (version 1.1), a free, open-source Add-In for Visual Studio 2008 for creating and editing Code Snippets directly within the IDE. Once you install it, creating a new Code Snippet is as easy as going to the File menu and creating a new Code Snippet File.

That is so cool! If you are interested go and download the Snippet Designer from the Codeplex website and give me more feedback.

Also, in the same article my friend Sara Ford had her blog featured. When I found out the Snippet Designer and Sara’s blog were in the magazine I quickly emailed to ask Sara if she knew about it. She already did and also had an extra copy of the magazine for me!

A functional take on console program loop in F#

MattManela — Tue, 14 Apr 2009 07:51:19 GMT

Often when learning a new technology I start with a simple console application in which the program is run in a loop it continues to prompt you for more input until you give some command like quit or exit or whatever you choose:

Enter input: someInput
someOutput
Enter input: otherInput
someoutPut
Enter input: quit
Thanks! Come again!

The code for this is in an imperative language is usually something like:

       1: while(true)

       2: {

       3:     Console.Write("\nEnter input:");

       4:     var line = Console.ReadLine();

       5:     if(line == "quit") break;

       6:     

       7:     doSomething(line);

       8: }

       9:  

      10: Console.WriteLine("Thanks! Come Again");

While reading some F# samples, I saw some code doing essentially the same thing which looked something like:

       1: Console.Write "\nEnter input:"

       2: let mutable input = Console.ReadLine()

       3: while input <> "quit"

       4:     do

       5:     

       6:     if input <> "quit" 

       7:     then

       8:         doSomething input

       9:         Console.Write "\nEnter input:" 

      10:         input <- Console.ReadLine()

Now this just feels dirty! In a functional language explicit loop constructs like a while loop feel wrong. I different way of doing this which is more functional is to create an infinite list of actions. Where each action represents one iteration of any of the above loops. Then you just execute each action until some condition is met (like seeing the input “quit”).

       1: let action = fun _ ->

       2:     Console.Write "\nEnter input: "

       3:     Console.ReadLine()

       4:  

       5: let readlines = Seq.init_infinite (fun _ -> action())

       6:     

       7: let run item = if item = "quit" 

       8:                 then Some(item) 

       9:                 else

      10:                     parse item 

      11:                     None

      12:  

      13: Seq.first run readlines |> ignore

      14: Console.WriteLine "Thanks! Come Again"

This code makes use of the Seq.init_infinite which create a infinite sequence and Seq.first which enumerates the sequence until the passed in function returns Some.

Synchronizing Scrollbars using JQuery

MattManela — Thu, 19 Mar 2009 23:29:11 GMT

I just wrote this simple plugin for JQuery which lets you synchronize the scroll bars of any collection of elements. This lets you move the scrollbar of one div it have the scrollbars’ of the rest of the divs move the same exact amount.

Here is the code:

        1: jQuery.fn.synchronizeScroll = function() {

       2:  

       3:            var elements = this;

       4:            if (elements.length <= 1) return;

       5:  

       6:            elements.scroll(

       7:            function() {

       8:                var left = $(this).scrollLeft();

       9:                var top = $(this).scrollTop();

      10:                elements.each(

      11:                function() {

      12:                    if ($(this).scrollLeft() != left) $(this).scrollLeft(left);

      13:                    if ($(this).scrollTop() != top) $(this).scrollTop(top);

      14:                }

      15:                );

      16:            });

      17:        }

Using this is SUPER simple. Lets say you have several divs defined as:

<div class=”scrollDiv” style=”overflow:auto;”> .. some large content</div>

To synchronize the scrollbars’ on all divs with the class scrollDiv all you need to write is:

$(“.scrollDiv”).synchronizeScroll();

Prime Factorization using Unfold in Haskell

MattManela — Tue, 17 Mar 2009 16:53:00 GMT

I randomly yesterday started thinking about the unfoldr function in Haskell while working out at the gym (how nerdy is that, I am lifting iron but thinking of functional programming). Unfoldr take a single and an unfolding function and turns it into a list (the opposite of fold). At the gym I was thinking about an application where I can use this and I decided that when I got home I would use it to write a prime factorization function. This is a method that when given a number returns the list of its prime factors.

It was easy to write the only part I am not pleased about is the code I used to deal with tuples. It seems clumsy and I am still looking for a way to clean that up.

One note: The code below references a list of prime numbers called primes , which is not shown.

Here is the code:

   1: primeFactors x = unfoldr findFactor x   2:                  where   3:                    first (a,b,c) = a   4:                    findFactor 1 = Nothing   5:                    findFactor b = (\(_,d,p)-> Just (p, d))   6:                                   $ head $ filter ((==0).first)    7:                                   $  map (\p -> (b `mod` p, b `div` p, p))  primes

This function will take any number which is greater than 1 and return a list of its prime factors. But don’t take my word for it, I wrote a quickcheck property to ensure the prime factors multiply back to the original number:

   1: prop_factors num =  num > 1 ==> num == (foldr1 (*) $ primeFactors num)

When running quickcheck on this property you see the following:

quickCheck prop_factors
OK, passed 100 tests.

My xUnit.net Visual Studio Code Snippets

MattManela — Tue, 03 Mar 2009 02:58:00 GMT

The xUnit .Net codeplex page lists one useful Visual Studio code snippet for creating a Fact. As you can tell I am fairly fond of code snippets so I created a few more which I use when writing xUnit.net facts. These are one line snippets that I find very convenient when writing my assertions.

Below is a table which shows the shortcut you use to access the snippet and the code the snippet generates

Shortcut	Snippet
ae	Assert.Equal($expected$,$actual$)
ane	Assert.NotEqual($expected$,$actual$)
an	Assert.Null($actual$)
ann	Assert.NotNull($actual$)
at	Assert.True($actual$)
af	Assert.False($actual$)

I have included a zip containing these snippets. Enjoy!

Code Assumptions

MattManela — Mon, 02 Feb 2009 07:13:42 GMT

My co-workers and I recently came across a piece of code which exposed some assumptions we had about the “correct” behavior of two functions; these assumptions turned out to be false. The code dealt with determining if the IP of a request coming into to a website matches a certain range of IP address. The range of IP address was defined in a config file and could look something like this:

156.27.1.2, 156.*.*.*, 127.0.0.*

Where the * acts as a wild card and each comma-separated IP format is matched against the incoming IP address. The code’s intended behavior is that specifying no IP address formats in the config would mean that no IP addresses would match the format. We noticed that this wasn’t holding true. We went to examine the code that was performing the matching (which none of us had written and sadly has NO test cases around it). The code boiled down to something like this:

        1: bool DoesIPMatchIPFormat(string incomingIpAddress, string ipFormatsFromConfig)

       2: {

       3:     foreach(var ipFormat in ipFormatsFromConfig.Split(','))

       4:     {

       5:         Regex re = ConvertFormatIntoRegex(ipFormat);

       6:         if(rs.Match(incomingIpAddress).Success) return true;

       7:     }

       8: }

Where ipFormatsFromConfig is the ip range of formats shown above separated by “,” or an empty string if no formats are given. On first glance we all were confused by why this didn’t work and then as we looked into it we realized we had made some incorrect assumptions.

First, we assumed that “”.Split(‘,’) would return a zero element array. This assumption is false. It returns a 1 element array containing the empty string.

After we learned this we encountered our second assumption. We assumed that a regular expression whose pattern was an empty string would not match anything. (ConvertFormatIntoRegex returned just that). This assumption is also false. After learning the true behavior, it makes sense why it behaves this way. (A DFA with only one state must accept every input. )

Our assumptions about the “correct” behavior of functions reflect similar mistakes made by all programmers; assuming that you don’t make these kinds of assumptions is a very dangerous way to program and reinforces the importance of unit testing.

Snippet Designer 1.1 Released

MattManela — Tue, 06 Jan 2009 05:11:28 GMT

I just released Snippet Designer 1.1. This is not a major release but just some bug fixes and often requested changes to make the snippet designer more useful.

Some of the most notable changes are:

Languages Service are turned OFF by default now. Since I was unable to figure out a way to host the C# and VB language services in the snippet editor without causing fake errors in projects I decided to give the users an option to turn them on or off. If you are ok with the fake error you can turn this back on but since it really annoyed me I have it off. I plan in a future release to provide some basic color coding outside of the language service so you can at least have color coded code.
Many more aspects of the plug in are now configurable through the options menu under Snippet Designer. you can now set the location of the snippet index, set preferences for which snippet languages you would like to appear in the snippet explorer.
Several bug fixes to how the highlighting of replacements works and performance improvements with it also.

Hopefully these changes will make it much more useful so please download it and try it out here.

The future…

My plans for the future are still up in the air but some of the things I would like to add are:

More bug fixes and more feature enhancements suggested by many helpful users on the Snippet Designer Codeplex page.
Ability to color code snippets without using the language service. I have a few options here I have been looking at.
Create a website to host snippets and allow you to consume and publish from Visual Studio to this website.

I don’t know how much time I will have to commit to any of these but hopefully I will be able to get more work done on this.

Thanks!