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<tr><td align="center" bgcolor="#8381de"><div class="skribetitle"><strong><big><big><big>14. Bigloo<br/>A ``practical Scheme compiler''<br/>User manual for version 3.2b<br/>June 2009 -- Command Line Parsing</big></big></big></strong></div><center>
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>Command Line Parsing</strong></font></th></tr>
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<tr><td valign="top" align="left"></td><td colspan="4" width="100%"><a href="bigloo-1.html#Acknowledgements">Acknowledgements</a></td></tr>
<tr><td valign="top" align="left">1</td><td colspan="4" width="100%"><a href="bigloo-2.html#Table-of-contents">Table of contents</a></td></tr>
<tr><td valign="top" align="left">2</td><td colspan="4" width="100%"><a href="bigloo-3.html#Overview-of-Bigloo">Overview of Bigloo</a></td></tr>
<tr><td valign="top" align="left">3</td><td colspan="4" width="100%"><a href="bigloo-4.html#Modules">Modules</a></td></tr>
<tr><td valign="top" align="left">4</td><td colspan="4" width="100%"><a href="bigloo-5.html#Core-Language">Core Language</a></td></tr>
<tr><td valign="top" align="left">5</td><td colspan="4" width="100%"><a href="bigloo-6.html#DSSSL-support">DSSSL support</a></td></tr>
<tr><td valign="top" align="left">6</td><td colspan="4" width="100%"><a href="bigloo-7.html#Standard-Library">Standard Library</a></td></tr>
<tr><td valign="top" align="left">7</td><td colspan="4" width="100%"><a href="bigloo-8.html#Pattern-Matching">Pattern Matching</a></td></tr>
<tr><td valign="top" align="left">8</td><td colspan="4" width="100%"><a href="bigloo-9.html#Fast-search">Fast search</a></td></tr>
<tr><td valign="top" align="left">9</td><td colspan="4" width="100%"><a href="bigloo-10.html#Structures-and-Records">Structures and Records</a></td></tr>
<tr><td valign="top" align="left">10</td><td colspan="4" width="100%"><a href="bigloo-11.html#Object-System">Object System</a></td></tr>
<tr><td valign="top" align="left">11</td><td colspan="4" width="100%"><a href="bigloo-12.html#Regular-parsing">Regular parsing</a></td></tr>
<tr><td valign="top" align="left">12</td><td colspan="4" width="100%"><a href="bigloo-13.html#Lalr(1)-parsing">Lalr(1) parsing</a></td></tr>
<tr><td valign="top" align="left">13</td><td colspan="4" width="100%"><a href="bigloo-14.html#Posix-Regular-Expressions">Posix Regular Expressions</a></td></tr>
<tr><td valign="top" align="left">14</td><td colspan="4" width="100%"><a href="bigloo-15.html#Command-Line-Parsing">Command Line Parsing</a></td></tr>
<tr><td valign="top" align="left">15</td><td colspan="4" width="100%"><a href="bigloo-16.html#Cryptography">Cryptography</a></td></tr>
<tr><td valign="top" align="left">16</td><td colspan="4" width="100%"><a href="bigloo-17.html#Errors-Assertions-and-Traces">Errors, Assertions, and Traces</a></td></tr>
<tr><td valign="top" align="left">17</td><td colspan="4" width="100%"><a href="bigloo-18.html#Threads">Threads</a></td></tr>
<tr><td valign="top" align="left">18</td><td colspan="4" width="100%"><a href="bigloo-19.html#Database-library">Database library</a></td></tr>
<tr><td valign="top" align="left">19</td><td colspan="4" width="100%"><a href="bigloo-20.html#Multimedia-library">Multimedia library</a></td></tr>
<tr><td valign="top" align="left">20</td><td colspan="4" width="100%"><a href="bigloo-21.html#Mail-library">Mail library</a></td></tr>
<tr><td valign="top" align="left">21</td><td colspan="4" width="100%"><a href="bigloo-22.html#Eval-and-code-interpretation">Eval and code interpretation</a></td></tr>
<tr><td valign="top" align="left">22</td><td colspan="4" width="100%"><a href="bigloo-23.html#Macro-expansion">Macro expansion</a></td></tr>
<tr><td valign="top" align="left">23</td><td colspan="4" width="100%"><a href="bigloo-24.html#Parameters">Parameters</a></td></tr>
<tr><td valign="top" align="left">24</td><td colspan="4" width="100%"><a href="bigloo-25.html#Explicit-typing">Explicit typing</a></td></tr>
<tr><td valign="top" align="left">25</td><td colspan="4" width="100%"><a href="bigloo-26.html#The-C-interface">The C interface</a></td></tr>
<tr><td valign="top" align="left">26</td><td colspan="4" width="100%"><a href="bigloo-27.html#The-Java-interface">The Java interface</a></td></tr>
<tr><td valign="top" align="left">27</td><td colspan="4" width="100%"><a href="bigloo-28.html#Bigloo-Libraries">Bigloo Libraries</a></td></tr>
<tr><td valign="top" align="left">28</td><td colspan="4" width="100%"><a href="bigloo-29.html#Extending-the-Runtime-System">Extending the Runtime System</a></td></tr>
<tr><td valign="top" align="left">29</td><td colspan="4" width="100%"><a href="bigloo-30.html#SRFIs">SRFIs</a></td></tr>
<tr><td valign="top" align="left">30</td><td colspan="4" width="100%"><a href="bigloo-31.html#Compiler-description">Compiler description</a></td></tr>
<tr><td valign="top" align="left">31</td><td colspan="4" width="100%"><a href="bigloo-32.html#User-Extensions">User Extensions</a></td></tr>
<tr><td valign="top" align="left">32</td><td colspan="4" width="100%"><a href="bigloo-33.html#Bigloo-Development-Environment">Bigloo Development Environment</a></td></tr>
<tr><td valign="top" align="left">33</td><td colspan="4" width="100%"><a href="bigloo-34.html#Global-Index">Global Index</a></td></tr>
<tr><td valign="top" align="left">34</td><td colspan="4" width="100%"><a href="bigloo-35.html#Library-Index">Library Index</a></td></tr>
<tr><td valign="top" align="left"></td><td colspan="4" width="100%"><a href="bigloo-36.html#Bibliography">Bibliography</a></td></tr>
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<a name="Command-Line-Parsing" class="mark"></a><a name="g17464" class="mark"></a><a name="g17466" class="mark"></a>
Bigloo supports command line argument parsing. That is, when an
application is spawn from an Unix shell, the <code id='code17468'
>main</code> function
is called and its argument is bound to the list of the command line
arguments, See <a href="bigloo-4.html#Modules" class="inbound">Module declaration</a>. The
<code id='code17469'
>args-parse</code> form may be used to parse these.<br/><br/><table cellspacing="0" class="frame" cellpadding="10" border="1" width="100%"><tbody>
<tr><td><a name="g17472" class="mark"></a><a name="args-parse" class="mark"></a><table width="100%" style="border-collapse: collapse;" frame="void" rules="none"><tbody>
<tr><td id="tc17476" align="left" colspan="1"><strong id='bold17474'
>args-parse</strong><em id='it17475'
> list rules [null-rule] [else-rule] ...</em></td><td id="tc17477" align="right" colspan="1">bigloo syntax</td></tr>
</tbody></table>
The argument <code id='code17481'
><em id='it17480'
>list</em></code> is a list of strings. <code id='code17483'
><em id='it17482'
>Rules</em></code> is defined by
the following grammar:<br/><br/><center id='center17493'
><table cellspacing="0" class="color" cellpadding="0" width="95%"><tbody>
<tr><td bgcolor="#ccccff"><pre class="prog" id='prog17491'
><rule> ==> (<code id='code17485'
>section</code> <string>)
| ((<option> <help>) <s-expression>)
| ((<option>) <s-expression>)
| ((<flag> <var> <var> ...) <s-expression>)
| ((<flag> <var> <var> ... <help>) <s-expression>)
<null-rule> ==> (<code id='code17486'
>()</code> <s-expression>)
<else-rule> ==> (<code id='code17487'
>else</code> <s-expression>)
<option> ==> <flag>
| <string><var>
<flag> ==> <string>
| (<string>+)
<var> ==> an identifier leaded by the <code id='code17488'
>?</code> character
<help> ==> (<code id='code17489'
>help</code> <s-expression>)
| (<code id='code17490'
>help</code> <string> <s-expression>)
</pre>
</td></tr>
</tbody></table></center>
Each elements of <code id='code17495'
><em id='it17494'
>list</em></code> are match against the <code id='code17497'
><em id='it17496'
>rules</em></code>. If one
of these matches, <code id='code17498'
>args-parse</code> proceeds as follows:<br/><br/><ol class="enumerate" id='enumerate17508'
><li>The matched argument elements of <code id='code17501'
><em id='it17500'
>list</em></code> are removed from the list.
</li>
<li>The <code id='code17503'
><s-expression></code> associated to the matching rule
is evaluated in an environment where the rule variables are bound.
</li>
<li>The argument parsing is resumed with the rest of <code id='code17506'
><em id='it17505'
>list</em></code>.
</li>
</ol></td></tr>
</tbody></table><br/>
In addition to parsing the command line arguments, <code id='code17511'
>args-parse</code> enables
help message printing. <br/><br/><table cellspacing="0" class="frame" cellpadding="10" border="1" width="100%"><tbody>
<tr><td><a name="g17514" class="mark"></a><a name="args-parse-usage" class="mark"></a><table width="100%" style="border-collapse: collapse;" frame="void" rules="none"><tbody>
<tr><td id="tc17518" align="left" colspan="1"><strong id='bold17516'
>args-parse-usage</strong><em id='it17517'
> fmt</em></td><td id="tc17519" align="right" colspan="1">bigloo procedure</td></tr>
</tbody></table>
This is a procedure of one argument, an boolean. <code id='code17522'
>Args-parse-usage</code>
constructs an help message from all the option described in a <code id='code17523'
>args-parse</code>
form. <code id='code17524'
>Args-parse-usage</code> is only defined in the <code id='code17525'
><s-expression></code>
of an <code id='code17526'
>args-parse</code> form.
</td></tr>
</tbody></table><br/>
At last, if no rule matches an argument and if the <code id='code17529'
>args-parse</code> form
contains an <code id='code17530'
>else</code> rule, this is evaluated. In the <code id='code17531'
><s-expression></code>
part of that rule, a pseudo-variable <code id='code17532'
>else</code> is bound to the unmatched
argument.<br/><br/>Here is an example of argument parsing deploying all the possible rules:<br/><br/><center id='center17559'
><table cellspacing="0" class="color" cellpadding="0" width="95%"><tbody>
<tr><td bgcolor="#ffffcc"><pre class="prog" id='prog17557'
>(<font color="#1919af"><strong id='bold28485'
>module</strong></font> <font color="#1919af"><strong id='bold28487'
>args-example</strong></font>
(main main))<br/><br/>(<font color="#6959cf"><strong id='bold28489'
>define</strong></font> (<font color="#6959cf"><strong id='bold28491'
>main</strong></font> argv)
(args-parse (cdr argv)
(section <font color="red">"Help"</font>)
((<font color="red">"?"</font>)
(args-parse-usage #f))
(((<font color="red">"-h"</font> <font color="red">"--help"</font>) (help <font color="red">"?,-h,--help"</font> <font color="red">"This help message"</font>))
(args-parse-usage #f))
(section <font color="red">"Misc"</font>)
(((<font color="red">"-v"</font> <font color="red">"--version"</font>) (help <font color="red">"Version number"</font>))
(print *version*))
((<font color="red">"-o"</font> ?file (help <font color="red">"The output file"</font>))
(<strong id='bold28505'
>set!</strong> *dest* file))
((<font color="red">"--input=?file"</font> (help <font color="red">"The input file"</font>))
(<strong id='bold28508'
>set!</strong> *input* file))
(else
(print <font color="red">"Illegal argument `"</font> else <font color="red">"'. Usage:"</font>)
(args-parse-usage #f))))
</pre>
</td></tr>
</tbody></table></center>
Invoking the compiled <code id='code17560'
>args-example</code> module could produce:<br/><br/><center id='center17566'
><table cellspacing="0" class="color" cellpadding="0" width="95%"><tbody>
<tr><td bgcolor="#ccffcc"><pre class="prog" id='prog17564'
>> bigloo.new args.scm
args.scm:
> a.out toto
Illegal argument `toto'. Usage:<br/><br/>Help:
?,-h,--help -- This help message<br/><br/>Misc:
-v,--version -- Version number
-o <file> -- The output file
--input=<file> -- The input file
</pre>
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