
Write once, run everywhere
==========================
  	Good idea, but still wishful thinking.

	From my experience I would like to add:
        "Write once, run everywhere, show the same behaviour!"	


Known bugs and failures:
========================

- Cut-and-paste
	I have not included any code for cut-and-paste. However,
	cut-and-paste should work fine under Unix. Cut-and-Paste
	also works in MS IE 3.0 under Mickeysoft Windows. For most of 
        the other platforms (MacOS etc.) and browsers (Netscape etc.)
        cut-and-paste does not work.

- Security exception
	Various versions of Netscape throw a security exception when
	I try to suspend the thread of the proof search. I have caught 
	this exception, but my literature does not tell me how to resume 
	safely from this exception. In effect the proof search enumerates 
 	all possible proofs for a sequent and subsequently stops. The user 
	has no control over how many proofs are shown (the corresponding 
	windows might appear over each other). This unintended behaviour 
	has been encountered in:
	
	  - Netscape Navigator 3.0 Gold under MS Windows'45
	  - Netscape Navigator 3.0 under MacOS
          - Netscape Communicator 4.0 under MacOS
	  - Netscape Navigator 3.01 Gold under Linux
	      (But here a "catch" of this exception and a "do nothing" 
	       helps. God knows why.)
	  - possible others

- Boxes around the sequents in proofs
	I have modified the "Label" class such that the "MyLabel" class 
	has a surrounding box. This improves the readability of the proofs.
	However,  this feature works ONLY under Unix. The boxes do not 
	appear in MS Windows and MacOS (reason unknown). 

- Flickering messages
	The applet prints some messages ("Grammar error", "No more proofs",
	"Not provable", etc.) in a field below the control buttons. 
	In some browsers the messages only flicker for a short time.
	Other browsers show the messages correctly (reason unknown).


The applet has been tested under (but see restrictions and bugs):
=================================================================

Linux:   
        Netscape Navigator 3.01 Gold
	Netscape Communicator 4.03, 4.04, 4.07 
        HotJava 1.1 beta2 (Linux-port)
        SUN's appletviewer for JDK 1.1.3
        
Win'95:
        Netscape Navigator 3.0 Gold
	Netscape Communicator 4.01a
        MS Internet Explorer 3.0.2
	MS Internet Explorer 4.0	

MacOS:  
	Netscape Navigator 3.0
	Netscape Communicator 4.0
	MS Internet Explorer 3.0.1b1 (PowerPC)


Any comments on success or failure for other
environments and platforms are appreciated.  

Christian.Urban@cl.cam.ac.uk
  
