NOTE:	This is an ObsoletePluginPackage. It has been superceeded by the wonderful ProgramsPlugin

[ move comments to PrologPluginDev ]

The PrologPlugin introduces the %PROLOG{...}% tag that:

• runs a TWiki:Codev/GnuProlog query
• replaces the tag with the run's output (you can also choose the output format)
• you can cache the result at save time to speed viewing the page
• you can impose a timeout to avoid runaway programs

• an object-oriented plugin.
• a plugin using a TWiki:Codev/PoorManCache
• a plugin that declares its syntax.
• so you need version 1.011 or above of Plugins.pm (attached) that handles objects and syntax declarations

++++ %SAVEDPROLOG{...}%: Cache of the PROLOG execution at save time (do not use)

++ Tips and tricks

• use when="save" to run the program at save time and cache the result
• use goal="<goal without closing dot>" to run a program without showing the prompt
• use dir="web" to run the program in the topic's web
  • useful to consult topics ... so that you can edit prolog programs as topics
    • yes, the META tags do not interfere, as they start with %, the prolog comment char
• use dir="topic" to run the program in the topic's attachments dir
  • useful if you want to create attachments rachable with the %ATTACHURL% tag
• use a looooong timeout together with when="save" to run long programs and cache the result

++ Installation

• install GnuProlog (see http://www.gnu.org/software/prolog)
• install the IPC::Run Perl module (from CPAN)
• install version 1.011 or above of Plugins.pm
• apply the attached patch needed to avoid processing verbatim tags in beforeSaveHandler
• unzip the PrologPlugin.zip package in the twiki directory (as usual)
  • Move the Plugins/PrologPlugin.txt* files to the TWiki web if you like
• check if the first example works

++ Settings

• Set DEBUG to 1 to see the command called
  • Set DEBUG = 0
• Description of this Plugin
  • Set SHORTDESCRIPTION = GnuProlog wrapper (and example of caching at save time)
• Default timeout for stopping long (runaway) runs
  • Set TIMEOUT = 2
  • NOTE: long running programs can be cached at save time by using the when="save" parameter together with a long timeout

++ BUGS

• Security Issue: the prolog program runs not (yet) chrooted

++ TODO

• run in a Safe box?
• run under chroot?
• compile a safe version of GnuProlog? <-- this one is better
• allow the usage of other implementations of prolog (SWI Prolog, Sicstus, ...)

++ Dependencies

• Plugins.pm version 1.011 or above
• the attached patch needed to avoid processing verbatim tags in beforeSaveHandler
• The GnuProlog prolog/constraint solver: http://www.gnu.org/software/prolog (tested with version 1.2.16)
• The CPAN module IPC::Run

++ Change history

• v. 1.000 : AndreaSterbini: first release

%PROLOG{
   goal="
      member(K,['TOPIC','WEB','ATTACHDIR','WEBDIR']),
      environ(K,V),
      format('\t* ~a = ~a\n',[K,V]),
      fail" 
}%

+++ Example cached at save time

<pre>
%PROLOG{
   initgoal="write('%RED%initgoal is running%ENDCOLOR%'),nl" 
   entrygoal="write('%BLUE%entrygoal is running%ENDCOLOR%'),nl" 
   querygoal="write('%GREEN%querygoal is running%ENDCOLOR%'),nl,halt" 
   when="save"}%
</pre>

initgoal is running
GNU Prolog 1.2.16
By Daniel Diaz
Copyright (C) 1999-2002 Daniel Diaz
entrygoal is running
| ?- write('querygoal is running'),nl,halt.
querygoal is running

+++ Example of timeout expiration

%PROLOG{
   goal="repeat,sleep(1),write(query),nl,fail" 
   format="
      <center>
      <table border='1'>
         <tr><th>stdout</th><th>stderr</th></tr>
         <tr><td><pre>$stdout&nbsp;</pre></td><td><pre>$stderr&nbsp;</pre></td></tr>
      </table>
      </center>"
   when="save"
}%

query
query
Prolog process timed out after 2 seconds. 

+++ Writing to an attachment

%PROLOG{
   goal="
      tell('pippo.txt'),
      write('| la vecchia con la borsa ... |'),
      nl,
      write('| ... salta il fosso senza rincorsa. |'),
      nl,
      told" 
   dir="topic" 
   when="save"
}%
| *Content of %ATTACHURL%/pippo.txt* | 
%INCLUDE{"%ATTACHURL%/pippo.txt"}%

Plugin Installation Instructions

Note: You do not need to install anything on the browser to use this plugin. The following instructions are for the administrator who installs the plugin on the server where TWiki is running.

• Install GnuProlog
• Install the IPC::Run Perl module (from CPAN)
• Install version 1.011 or above of Plugins.pm
• Apply the attached patch needed to avoid processing verbatim tags in beforeSaveHandler
• Unzip the PrologPlugin.zip package in the twiki directory (as usual)
  • Move the Plugins/PrologPlugin.txt* files to the TWiki web if you like
• Check if the first example works

Plugin Info

Plugin Author:	TWiki:Main/AndreaSterbini
Plugin Version:	22 Aug 2003 (V1.000)
Change History:
22 Aug 2003:	First release v1.000
CPAN Dependencies:	IPC::Run
Other Dependencies:	* Plugins.pm version 1.011 or above * the attached patch needed to avoid processing verbatim tags in beforeSaveHandler * The GnuProlog prolog/constraint solver (tested with version 1.2.16)
Perl Version:	5.005
Plugin Home:	http://TWiki.org/cgi-bin/view/Plugins/PrologPlugin
Feedback:	http://TWiki.org/cgi-bin/view/Plugins/PrologPluginDev

Related Topics: TWikiPreferences, TWikiPlugins

-- TWiki:Main/AndreaSterbini - 22 Aug 2003