			Updates up to SEQUEL 2.2

The first public issue of SEQUEL was SEQUEL 2.1 in September 1992.  The 
updates are as follows:-

2.2 (October 1992)

	The function (suppress [<list of symbols>]) of type 
(list symbol) -> bool has been introduced.  It removes each symbol from the
graphical interface.  The use of suppress is that it allows
rewrite rules to be banished from view if they become redundant due to the 
evolution of powerful tactics derived from them.

	The function (document-theory <string>) has been introduced.  It
allows info. to be attached to the name of a theory which is fed into a
pop-up window.  Otherwise it works like document-tactic.

	The options a (abort) and j (jump) have been introduced to the trace
package.  In step mode, typing a + RETURN will abort the trace to the top
level; typing j + RETURN will unstep the trace.

	All problems entered to the proof tool are entered as Lisp lists;
i.e. beginning with ( and ending with ).  So (p & q) * thm (in the 2.1 
manual) would be entered as ((p & q) * thm).  

3.0 (November 1992)

	XTT 1.1 is replaced by XTT 2.0 which in addition to the types
recognised by XTT 1.1 recognises characters, floating-
point and rational numbers as types.  Many Lisp system functions are now
type-checkable that operate over these types.  For a list of functions 
recognised by XTT 2.0, see the file settings.lisp. The functions 
prefixed by x (eg xposition) are tidied up versions of the Lisp 
equivalents (eg position) and do much the same job.  However where 
for example, position returns nil xposition returns an error message.
These changes were necessary in order to give these functions proper
types.

	The SEQUEL -> Lisp compiler in this version will insert type
declarations into the generated Lisp code providing that type-checking is
enabled.  This can produce speedups from 16-75% in the performance of 
SEQUEL-generated Lisp after it is run through the compiler.

3.1 (November 1992)

	Two bugs were found in 3.0.  The function / would not type check
and t-exprs could not be type-checked unless files were consulted through
call-framework.  These bugs were due to simple initialisation errors in
settings.lisp which have been corrected.

	The file ll.lisp contains a new load routine that allows the
user to enter his/her own pathnames and override the default ones
when loading the graphical interface.

3.2 (November 1992)

	Two errors with the signatures of length and < were corrected.

3.3 (December 1992)

        Andrew Adams detected several errors in XTT and these were corrected
in 3.3.

3.4 (January 1993)

        Andrew detected more errors in XTT and these were corrected.  Also
several primitives crashed on receiving the empty proof and did not 
behave as identity functions.  A bug was found in the behaviour of rewrites
using the extra optional parameter.  These bugs were corrected for 3.4.

	3.4 includes facilities for defining side-conditions in sequent 
calculus axioms.

3.5 (February 1993)

	Daniel Basterfield detected an error in the implementation of pattern-
matching in 3.4.  This was corrected in 3.5.

4.0  (March 1993)

	Side-conditions introduced in  3.4 were greatly amplified in power
and many of the implementation restrictions on their use were lifted.
Side conditions are fully type checked in 4.0

4.1 (April 1993)

	Andrew detected an error in the type checking of eval which was
corrected in 4.1.

4.2  (April 1993)

	Side-conditions bug fixed.

4.3 (April 1993)

        repseq introduced as an extra primitive.

4.4-4.5 (May - June 1993) 

	Divers bugs corrected.

4.6 (July 1993) 

        Anonymous functions introduced; backtracking refined.

5.2 (August 1993)

	XTT 3.0 introduced and metarewriting facility included.

6.0 (December 1993)

	Type operators are definable

7.0 (January 1994)

	Fastcode introduced.
