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<TITLE> Christian Urban </TITLE>
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<B>Links</B><BR>
<A HREF="http://www4.in.tum.de/~urbanc/index.html">Home</A><BR>
<A HREF="http://www4.in.tum.de/~urbanc/Cut/cutapplet.html">Applet Home</A><BR><BR>
<B>Java Versions</B><BR>
<A HREF="http://www4.in.tum.de/~urbanc/Cut/CL.html">CL</A><BR>
<A HREF="http://www4.in.tum.de/~urbanc/Cut/LJT.html">LJT</A><BR>
<A HREF="http://www4.in.tum.de/~urbanc/Cut/ND.html">ND</A><BR><BR>
<B>Plugin Versions</B><BR>
<A HREF="http://www4.in.tum.de/~urbanc/Cut/CL-plugin.html">CL</A><BR>
<A HREF="http://www4.in.tum.de/~urbanc/Cut/LJT-plugin.html">LJT</A><BR>
<A HREF="http://www4.in.tum.de/~urbanc/Cut/ND-plugin.html">ND</A><BR>
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<A HREF="http://isabelle.in.tum.de/nominal/">
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<A NAME="Home"></A>
<H2>Applet for Cut-Elimination and Normalisation </H2>
<FONT COLOR="#800000"><B>Warning:</B></FONT>
These pages are still under construction and designed for the conoscenti
only. If you encounter any problems, email me. Some general information
about the applet is given below.<p>
The applet is outcome of my interest in cut-elimination. It helps to
explore reduction trees in a slight variant of the sequent calculus LK,
and also reduction trees in Herbelin's calculus LJT (as presented
<A HREF="http://www-theory.dcs.st-and.ac.uk/~rd/publications/MJES/">here</A>)
and in the standard formulation of natural deduction for intuitionistic
logic. Given for example the following classical sequent proof<p>
<center>
<IMG SRC="Cut/ex1.jpg" ALT="" ALIGN=CENTER>
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you can produce by simply pressing the buttons L and R the following
two cut-free proofs.<p>
<center>
<IMG SRC="Cut/ex2.jpg" ALT="" ALIGN=CENTER>
<IMG SRC="Cut/ex3.jpg" ALT="" ALIGN=CENTER>
</center><p>
If you ever have done cut-elimination by hand, then you
know how useful this applet is.<p>
<img ALIGN=BOTTOM ALT="" SRC="new.gif"> The applet is particularly useful for doing
some calculations finding out what the (proof-theoretical) semantics for classical logic
should look like. Some informal notes are
<A HREF="http://www4.in.tum.de/~urbanc/Cut/notes.html">here</A>.
<p>
The applet needs at least <B>Java 1.2</B> including the
<B>Swing</B> libraries. Some browsers support these requirements
directly, and if you are one of the lucky to have such a browser
you can access the three calculi by pressing on one of the
following links.
<UL>
<LI><A HREF="http://www4.in.tum.de/~urbanc/Cut/CL.html">CL - cut-elimination
in classical logic</A>
<LI><A HREF="http://www4.in.tum.de/~urbanc/Cut/LJT.html">LJT - cut-elimination in
intuitionistic logic</A>
<LI><A HREF="http://www4.in.tum.de/~urbanc/Cut/ND.html">ND - normalisation in
intuitionistic natural deduction</A><p>
</UL><p>
If not, then your browser can most probably run the applet with
the help of a Java plugin. In this case follow the links below.
<UL>
<LI><A HREF="http://www4.in.tum.de/~urbanc/Cut/CL-plugin.html">CL - cut-elimination
in classical logic</A>
<LI><A HREF="http://www4.in.tum.de/~urbanc/Cut/LJT-plugin.html">LJT - cut-elimination in
intuitionistic logic</A>
<LI><A HREF="http://www4.in.tum.de/~urbanc/Cut/ND-plugin.html">ND - normalisation in
intuitionistic natural deduction</A><p>
</UL><p>
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For the curious: the applet is written in MLJ, which is being
developed by
<A HREF="http://research.microsoft.com/~nick/">Benton</A>,
<A HREF="http://research.microsoft.com/~akenn/">Kennedy</A> and
<A HREF="http://research.microsoft.com/~crusso/">Russo</A>.
MLJ is a dialect of SML that provides access to Java libraries; in my
opinion it is a really nifty language! I am using an improved version of
the MLJ-0.2 compiler.
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Last modified: Sat Mar 3 05:16:36 CET 2007
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