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<h2>Coco/R for Visual Studio.Net</h2>
<p>by Pascal GANAYE</p>
<p><img src="vsCoco.png" alt="Sample Image - maximum width is 600 pixels" width=639 height=453></p>
<!------------------------------- STEP 3 --------------------------->
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<h2>Introduction</h2>
<p>I have been publishing one or two article about formula evaluation, and so
far all programs were written manually. For a recent project I need to parse
far more complex grammars and I really needed some help.<br>
<p>I had a look on the internet and I found a project called <a href="http://www.ssw.uni-linz.ac.at/Research/Projects/Coco/">Coco/R</a>
from the Johannes Kepler Universität Linz. This is how they discribe their
product : "Coco/R takes a compiler description in the form of an attributed
grammar (EBNF syntax with attributes and semantic actions) and translates it
into a scanner and a recursive descent parser.... Coco/R has been used successfully
in academia and industry. It combines the functionality of the well-known Unix
tools Lex and Yacc".
<p>I used Coco for a while and despite being extremely good I found working with
it rapidly frustrating because I had to run it manually and it was not really
well integrated with Visual Studio.
<h2>Background</h2>
<p>Anyone wanting to use this tool should be familiar with EBNF grammars. There
is several good introduction available on the internet.
<p>I also particularly recommend the reading of <a href="http://www.ssw.uni-linz.ac.at/Research/Projects/Coco/Doc/UserManual.pdf">the
Compiler Generator Coco/R User Manual</a>
<h2>Installing vsCoco</h2>
<p>You need to download and run the file <code>vsCocoRegistration.exe</code>. The
registration should work fine with Visual Studio 2003. </p>
<p>If it doesn't work with your version, please post in the forum below. If you
are able to fix the vsCoCoRegistration please
<script language="JavaScript" >// <!-- Encryption www.ganaye.com v1.0
document.write("<a href=\"mailto:\160asc\x61\x6cc\160\100\147a\x6e\141y\x65\56c\157m?subject=[vsCoco] ...\">write to me</a>"); //-->
</script>
the updated source.</p>
<h2>Using vsCoco</h2>
<p>To start with you can try to play with the Calculator sample I provided in
the download.
<p>The calculator calculates formula like <code>12+34*55/2</code> .
<p>The sample contains only 5 lines of csharp code.
<pre>private void button1_Click(object sender, System.EventArgs e)<br>{<br> Parser p = new Parser(comboBox1.Text);<br> p.Parse();<br> textBox1.AppendText(">" + comboBox1.Text + "\r\n" <br> + p.result.ToString() + "\r\n");<br>}
</pre>
<p>As you can see most of the login must be in the Parser Object.</p>
<p>The parser is created automatically from this grammar:</p>
<pre>COMPILER calc
public double result = 0;
IGNORECASE
// The $L option let you compile directly within your grammar
// You can comment and uncomment the line to fit your development requirements.
$L
/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/
CHARACTERS
digit = "0123456789".
cr = '\r'.
lf = '\n'.
tab = '\t'.
TOKENS
number = digit {digit} ['.' {digit}].
// We don't use comments here but this is only a sample
COMMENTS FROM "//" TO cr lf
IGNORE cr + lf + tab
PRODUCTIONS
/*------------------------------------------------------------------------------*/
/*------------------------------------------------------------------------------*/
OPERAND<out double val>
= (. val = 0; .)
(
number (. val = Double.Parse(t.val,
System.Globalization.NumberStyles.Float,
System.Globalization.CultureInfo.InvariantCulture);
.)
| "(" EXPR<out val> ")"
).
// Priorities in FGL
//
// () (Parenthesis)
// 10 - (Unary neg)
// 09 * / (Multiply and Divide)
// 07 + - (Add and Substract)
/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/
EXPR10<out double val>
= (. bool neg=false; .)
{
( '-' (. neg=!neg; .)
| '+' (. /*nothing to do*/ .)
)
}
OPERAND<out val> (. if (neg) val*=-1; .)
.
/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/
EXPR09<out double val>
=
EXPR10<out val>
{ (. double val2; .)
( '*'
EXPR10<out val2> (. val*=val2; .)
| '/'
EXPR10<out val2> (. val/=val2; .)
)
}
.
/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/
EXPR<out double val>
=
EXPR09<out val>
{ (. double val2; .)
( '+'
EXPR09<out val2> (. val+=val2; .)
| '-'
EXPR09<out val2> (. val-=val2; .)
)
}
.
/*--------------------------------------------------------------------------*/
/*--------------------------------------------------------------------------*/
calc
=
EXPR<out result>.
END calc.
</pre>
<p>This grammar is fairly standard one. </p>
<p>If I try to read it in English it would say:</p>
<ul>
<li>This grammar will produce a parser called calc.</li>
<li>Calc parser return expressions</li>
<li>An expression can be a sum or if not a product of signed numbers.</li>
<li>The multiplication should be done before the additions however the minus
and plus sign have more priority if they are signs.</li>
</ul>
<p>As you can see there is more complexity than it looks.</p>
<p>This is a bit hard for me to describe what this grammar does and how it works
and this is not my goal.</p>
<p>What I would like to share with you is this tool and hopefully raise an interest
for Compiler's compilers if you are new in this subject.</p>
<h2>How does it work ?</h2>
<h2>Coco Modifications - 1 : the #line</h2>
<p>I made several major modifications to Coco/R</p>
<p>First I wanted to trace within the grammar.</p>
<p>This was the easy part, I modified Coco source file and added the $L option.</p>
<p>If you insert $L in the beginning of your grammar, Coco compiler wil add many
#line in your code.</p>
<p>For example:</p>
<pre>
COMPILER calc
public double result = 0;
IGNORECASE
// The $L option let you compile directly within your grammar
// You can comment and uncomment the line to fit your development requirements.
$L
</pre>
...
<pre>
OPERAND<out double val>
= (. val = 0; .)
(
number (. val = Double.Parse(t.val,
System.Globalization.NumberStyles.Float,
System.Globalization.CultureInfo.InvariantCulture);
.)
| "(" EXPR<out val> ")"
).
</pre>
<p>Will generate:</p>
<pre> void OPERAND(
#line 31 "C:\dotnet\vsCoco\Calculator\Calc.atg"
out double val
#line hidden
) {
#line 32 "C:\dotnet\vsCoco\Calculator\Calc.atg"
val = 0;
#line hidden
if (la.kind == 1) {
Get();
#line 34 "C:\dotnet\vsCoco\Calculator\Calc.atg"
val = Double.Parse(t.val,
System.Globalization.NumberStyles.Float,
System.Globalization.CultureInfo.InvariantCulture);
#line hidden
} else if (la.kind == 2) {
Get();
EXPR(
#line 38 "C:\dotnet\vsCoco\Calculator\Calc.atg"
out val
#line hidden
);
Expect(3);
} else SynErr(9);
}
</pre>
<p>This <code>#line</code> are very helpful, the Visual Studio IDE understand
it well and let you debug your generated program using the original source grammar.</p>
<p>I find it very useful; you can comment and uncomment the $L line to fit your
development requirements .</p>
<h2>Coco Modifications - 2 : A real Visual Studio Custom tool</h2>
<p>My second goal was to run Coco directly from Visual Studio as a custom tool,
rather than having to use batch files.</p>
<p>The main advantage of a custom tool is that it will be automatically called
when the source grammar changes and not at each compile.</p>
<p>Visual studio publishes an interface called <code>IVsSingleFileGenerator</code>.</p>
<p>This interface defines two methods: </p>
<ul>
<li><code>int DefaultExtension(out string)</code></li>
<li><code>int Generate(string, string, string, System.IntPtr[], out uint, Microsoft.VisualStudio.Shell.Interop.IVsGeneratorProgress)</code></li>
</ul>
<p>Providing this two interface is the base of the work needed to make a visual
Studio Custom tool.</p>
<h3>Coco Modifications - 3 : An installer for the Visual Studio Custom tool</h3>
<p>With the good information, this is after all fairly straight forward. I used
and modified the GotDotNet User Sample: <a href="http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=4AA14341-24D5-45AB-AB18-B72351D0371C">BaseCodeGeneratorWithSite</a>.</p>
<p>Now that we have a dll which can be a Visual Studio plugin, you need to register
it. This could prove a lot harder than expected. Fortunately I read a excellent
article called <a href="http://www.codeproject.com/dotnet/Custom_Tool_Registration.asp">Automated
Registration of Visual Studio Custom Tools</a> by <a href="http://www.codeproject.com/script/profile/whos_who.asp?id=1113856">Michael
McKechney</a>.</p>
<p>I butchered his sample program and produced vsCocoRegistration.exe.</p>
<h2>Known bugs</h2>
<p>vsCocoRegistration does not yet works with all version of Visual Studio.net.
This is just a question of changing the Registry GUIDs but I don't have that
many version to test it with. So feel free to ask in the forum below.
<h2>Links</h2>
<p><a href="http://www.ssw.uni-linz.ac.at/Research/Projects/Coco/">The Compiler
Generator Coco/R</a> by Hanspeter Mössenböck, Albrecht Wöß,
Markus Löberbauer, University of Linz </p>
<p><a href="http://en.wikipedia.org/wiki/LL_parser">LL parser</a> From Wikipedia,
the free encyclopedia.</p>
<p>GotDotNet User Sample: <a href="http://www.gotdotnet.com/Community/UserSamples/Details.aspx?SampleGuid=4AA14341-24D5-45AB-AB18-B72351D0371C">BaseCodeGeneratorWithSite</a>
</p>
<p><a href="http://www.codeproject.com/dotnet/Custom_Tool_Registration.asp">Automated
Registration of Visual Studio Custom Tools</a> article from by <a href="http://www.codeproject.com/script/profile/whos_who.asp?id=1113856">Michael
McKechney</a>. </p>
<h2>History</h2>
<p>October 29th 2005 - First release.
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