Christian Urban

Links Home Applet Home Java Versions CL LJT ND Plugin Versions CL LJT ND | ## Normalisation in intuitionistic natural deduction This applet implements the bog-standard version of intuitionistic natural deduction. If you are familiar with any textbook on proof theory (e.g. this one), then most things will look very familiar to you. Note that natural deduction is here implemented in `sequent style'.
How to use it? If your browser is working correctly, then you will see a window with two examples (more added if I have time or you suggest one). When you press on one of the buttons, a new window will pop up. What follows is a brief explanation of all the features available in this window.
Buttons and Keys The buttons `fire' beta-redexes (nothing surprising here). If you use the left mouse button for pressing on those buttons, then the new proof will appear inside the window. Whereas if you use the right mouse button, a new window will pop up and the new proof will be displayed in this window. Use the right mouse button if you want to compare a proof and its reduct. The keys Page-up and Page-down zoom in or out of a proof respectively.
Menu Functions Zoom in and Zoom out work like Page-up and Page-down, respectively. Unicode If this radiobutton is switched on, logic symbols are displayed in unicode, otherwise in ascii. (This is for the poor guys who have a browser and/or operating system which cannot handle unicode.) Labels As mentioned earlier the sequents are composed of two sets of labelled formulae, not multisets of formulae as in the standard formulation of sequent calculus. Enabling this radiobutton causes that labels are drawn. Use this when you are unsure where implicit contractions are. Compact printing Usually formulae are weakened only in axiom. If this radiobutton is switched on (default), then, in order to save space, formulae are weakened as soon as possible.

Last modified: Sat Mar 3 05:16:58 CET 2007