In this file I'll try to record the differences in the various patchlevels
of Otter 3.0.  The most recent entries are at the end.

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Otter 2.99 released November 25, 1993.

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   Many small changes.

Otter 3.0.0 released January 24, 1994.

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   Check for errors when reading clause id from terminal, flag
   interactive_given, routine find_interactive_clause().

   FormEd only: parsing strings read interactively, routine str_2_formula().

   Problem with dynamic demodulators that have answer literal before equality.
   (Answer lits are not propogated during demodulation, so I can't see any use
   for answer lits on input demodulators, but they can occur indynamic
   demodulators.)  Changed contract_lin(), insert_imd(), delete_imd(),
   new_demod(), back_demod(), post_process(), so that they use ith_literal(),
   which skips answer lits.  Also changed check_input_demod() to allow
   answer lits on input demodulators.

Otter 3.0.1 - DOS version released Feb 22, 1994.
   
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   Optimized forward subsumption for nonunit clauses: require that found
   literal be first literal.  Routine forward subsume() in file clause.c.
   
   Mar. 21, 1994.  Bug in unit deletion when answer literals with fresh
   variables introduced.  Factor_simp crashes because variables not renumbered.
   Fix: in unit_del(), renumber variables if ANY answer literals
   introduced.  Result is otter301b.
   
   March 31, 1994.  Added code to translate otter input for Davis-Putnam
   model searcher: set(dp_transform).  Result is otter301dp.

   Apr. 13, 1994.  Slight change to Davis-Putnam translator so that it
   outputs vraiable names with "v" instead of plain integers.

   May 23, 1994.  Kunen convinced me to make answer literals sound.  In
   particular, if they occur on demodulators, then they should be inherited
   by rewritten clauses.  Since inheriting during demodulation would
   slow it down, would take a lot of time to code, and would be of
   questionable value, I'll simply not let demodulators have answer literals.
   Fix: check_input_demod(), pre_process(); new routine
   num_literals_including_answers().  NOTE: Subsumption still ignores
   answer literals, and factoring still attempts to factor answer literals.
   Result is otter301c.

   June 8, 1994.  In proggen() (process generated clauses) moved cl_merge()
   after factor_simplify() to make construction of proof objects easier.

   June 8, 1994.  When input clauses are changed in procgen() (due to
   flag process_input), e.g., by demod, unit_del, or factor_simp, the
   original input clause is now assigned an ID and appears in proofs.
   The new inference rule "copy" indicates this.  Changed header.h, 
   pre_process(), and print_clause().  Motivation: to make proofs easiser
   to read and to ease proof object construction.

   June 8, 1994.  When equality literals are flipped, add an entry to
   the justification list.  Changed order_equalities(), order_equalities_lrpo(),
   post_process(), header.h, proc_gen(), print_clause(), maybe others??.
   Motivation: to make proofs easiser
   to read and to ease proof object construction.

   June 9--16, 1994.  Various changes related to construction of proof objects.

Otter 3.0.2 - UNIX version released June 17, 1994

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