File: ChangeLog

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swi-prolog 3.1.0-2
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			SWI-Prolog ChangeLog
			====================
VERSION 3.1.0
=============

  * ADDED: PL_put_string_nchars() to register strings using length/ptr    

  * FIXED: bug in the stack-shifter, introduced in 3.0.0

  * FIXED: configure option --disable-mapped-stacks

  * ADDED: configure option --disable-segv-handling

  * ADDED: Mapping signals (software interrupts) onto Prolog predicates
    or exceptions.  See on_signal/3.

  * MODIFIED: signal-handling using PL_signal(): the handler can now
    safely call Prolog.

  * MODIFIED: PL_throw() now performs a longjmp(), instead of returning
    failure.  PL_raise_exception() replaces the old PL_throw()

  * FIXED: FreeBSD testing for rlim_t type (configure).  Thanks to
    Colin E. Johnson.

  * PERFORMANCE: Added indexing for non-tagged numbers (> 16M)

  * FIXED: current_stream/3 for streams having an alias name.  Fix 
    also affects other stream-related predicates returning an aliases
    stream.

  * FIXED: added space in write(a+ -1).

VERSION 3.0.0
=============

  * FIXED: Actually test for GCC-2 feature to handle label-addresses.
    Should fix compilation on Rapsody, where cc says it is gcc-2, but
    the gcc extensions are not enabled (by default).

  * FIXED: Detection of topOfHeap() on m68k linux (and other linux brands),
    using a patch contributed by Roman Hodek.
    
  * FIXED: Garbage collection error, resulting in a false `early reset'
    in a specific combination on call-back from C to Prolog and 
    choicepoints.  With thanks to Lourens van der Meij for reporting
    and localising the problem.

  * ADDED: PL_cons_functor_v() to create a functor from a vector of
    term-references.

  * FIXED: discontiguous and multifile cause the predicate to be considered
    `defined'.  Thanks to Paulo Moura.

  * ADDED: prolog_list_goal/1 hook to intercept the 'L' command from the
    debugger.

  * FIXED: configure detection of type rlim_t on some platforms.  Thanks to
    Volker Stolz.

  * MODIFIED: <module>:<head> :- <body> is now compiled differently from
    <module>:(<head> :- <body>).  The clause is added to <module>:<head>,
    but <body> is executed in the context of the definition module.  This
    behaviour is compliant with Quintus and SICStus Prolog, and required
    to deal with the XPCE 5.0 class-compiler.  In most cases, this just
    allows to remove now redundant module specifiers.  In the rare cases
    the old behaviour is required, just but enclose the close in braces.

  * FIXED: abolish/[1,2] on an imported predicate.

  * ADDED: Putting `resources' into a saved state.  Especially for dealing
    with XPCE (graphics) resources.  See resource/3, qsave_program/[1,2],
    open_resource/[3,4], plrc(1), PL_open_resource().

  * FIXED: Sfread() and Sfwrite() to return proper value on short read/write.

  * FIXED: Copy-problem in Which() (pl-os.c).  Made the problem below
    appearant.

  * FIXED: Symbols() to deal with x-only executables (Unix).  Thanks to
    Gernot Salzer (caused a crash).

  * FIXED: Docs for PL_cons_list().  Thanks to Ivan Karski.

  * ADDED: PL_cons_functor() the first argument may now also appear in
    the argument list.

  * FIXED: putNum()/getNum() format to deal with any value that can
    be represented in a long.  Fixes an assertion failure while booting
    on some platforms.

  * FIXED: Quoted write in feature(character_escape, true) is effective
    to write the atoms such that they can be read back.  Spotted by
    Bernd Werner.

  * ADDED: Seek/4, Quintus compatible implementation for seeking to an
    indicated position in a stream.

  * FIXED: Various traceports to make Prolog exit on reading end-of-file,
    rather then entering an endless loop.

  * FIXED: put/[1,2] to raise an exception on IO errors.  Patched
    SIGPIPE handling to clear the buffer of the offending stream,
    so a subsequent close() on the stream will not cause another
    SIGPIPE.

  * MODIFIED: file_directory_name/2 output never contains a trailing
    /.  If no directory is present, the result is '.'.

  * DELETED: -B command-line switch

  * DELETED: old save/restore facilities.  

VERSION 2.9.10
==============

  * ADDED: dup_stream/2 to copy stream handles.

  * ADDED: Allow for specifying stream alias-name to PL_open_stream(),
    also used by open_null_stream/1, so open_null_stream(null) will make
    `null' an aliased null-stream.

  * UPDATED: Some parts of the documentation.

  * FIXED: Control-C handling on some platforms (notably Solaris 2.5).

  * ADDED: options close_on_abort and buffer to open/4.

  * FIXED: write(not (a,b)) ommited the space and wrote not(a,b).  Thanks
    to Stefan Mueller.

VERSION 2.9.9
=============

  * FIXED: Portability problems for Solaris 2.6.

  * FIXED: throwing Prolog exceptions on `Broken Pipe' in flush/0 and
    flush_output/1.

  * FIXED: detection of limit on datasize on SGI platform.  Thanks to
    Marcello Balduccini.

  * FIXED: Possibility of a crash in Symbols(), notably affecting embedded
    systems (at startup).  Thanks to Anton Eliens.

The 4 bugs below were reported by Luc Van Oostenryck.  Thanks.

  * FIXED: concat_atom/3 if the separator is not an atom.

  * FIXED: arg(0, Term, Arg) to fail

  * FIXED: atom_char(abc, X) to raise an instantiation fault if the length
    of the atom is not 1.  Also, return integers in the range [1..255] instead
    of [-128..127].

  * FIXED: -0xff is now read as -255.  Not sure if -(255) would not be a
    better idea!?

VERSION 2.9.8
=============

  * WIN32: Replaced various C runtime functions by their native Win32
    versions.

  * FIXED: Calling module transparent predicates from the outer foreign
    context using context module NULL to call in module "user", rather than
    in the definition module of the predicate.  Found by Stephane Berhault.

  * FIXED: Early switch off the tracer after an abort to avoid tracing
    the hooks.

  * ADDED: explain/1 reporting references to undefined predicates (i.e. which
    clauses reference the undefined predicate).  Also explain/1 reporting
    references to XPCE methods.

  * FIXED: explain/1 reporting non-existing references to compound terms.

VERSION 2.9.7
=============

  * FIXED: avoid some warnings to get clean compilation on GCC 2.8.0.

  * FIXED: detection of discontiguous predicates (avoids false alarm).

  * ADDED: Predicate definition for (*->)/2, mainly to allow for testing
    for its existence and avoid redefinition.

  * ADDED: Options to qsave_program/2 may be specified as Name(Value)
    or Name = Value.

  * FIXED: `map' option of qsave_program/2.

  * FIXED: handling of dynamic predicates import/export by
    qsave_program/[1,2].  found by Lourens van der Meij.

  * PORT: fixed pl-load.c for systems supporting the ELF dynamic load
    functions, but not RTLD_LAZY (FreeBSD?)  Lost the name of the guy
    pointing me to this problem.  Thanks anyway!

  * FIXED: handling of a functor as key for recorded and frieds, found by
    Lourens van der Meij.

  * FIXED: current_stream/3 if a current stream refers to a pipe.  Found
    by Robert van Engelen.

  * FIXED: dereferencing symbolic link of argv[0] to find the `real'
    symbol file.  Reported by Milan Zamazal, where this problem caused
    a crash when running SWI-Prolog using M-x run-prolog under Emacs.

VERSION 2.9.6
=============

  * MODIFIED: list_to_set/2 retains the first, rather then the last
    occurrence of duplicate members to the set.

  * FIXED: flag/3 using floating-point numbers for machines that cannot
    address doubles on 4-byte alignment (most RISC processors).

  * FIXED: foreign-reference handling of exception terms, causing garbage
    collection problems.  Reported by Robert van Engelen.

  * PORT: improved detection and placement of mmap()-ed stacks (Unix sparse
    stack-management) with help of Marcello Balduccini.

  * FIXED: clause/3 to add/remove predicate reference-count while holding
    a choicepoint to the predicate.  Reported by Marcello Balduccini.

  * ADDED: -c flag to plld to turn it into `plcc', just compiling .c or
    .cc files.  Thanks to Marcello Balduccini.

  * MODIFIED: write/1 and friends now only insert spaces before and
    after operators if these are required to be a valid term for read/1.
    The only exception is ,/2, which is written using a space after the
    symbol.  NOTE: foreign packages including <SWI-Stream.h> need
    to be recompiled!!!

  * FIXED: current_predicate/2 not consider abolished predicates that
    still exist as `current', so current_predicate(_, Goal), Goal is
    guaranteed not to raise an exception on Goal.  Should fix recent
    reconsult problems in XPCE.

  * ADDED: user:message_hook/3 hook for print_message/2 (provisional).

  * MODIFIED: Hooks installed by PL_initialise_hook() are called *before*
    the saved-state is loaded, but after the heap is initialised.  This
    implies only foreign predicates may be called from this hook now.

  * FIXED: testing of write-permissions for the library index for
    make/0.

  * MODIFIED: Toplevel queries are now read from user_input, rather
    than from the current input stream.

  * ADDED: feature(history, Depth).  If 0, no history and no history-prompt
    are provided.  This is the default if feature(readline, true) succeeds.

  * FIXED: set_feature(Name, Integer)

  * FIXED: chdir/absolute_file_name problem, reported by Machiel Jansen.
    Thanks.

  * FIXED: erase/1 on records referenced by recorded/3 choicepoints.  Thanks
    to Robert van Engelen.

  * FIXED: Reference direction in recorded/3 (also used by findall/3 and
    friends).

  * FIXED: Removed various warnings for SunSoft cc compiler.  Fixed
    one error reported by this compiler.

  * FIXED: Cite references in online documentation.  Modified/Cleaned
    man/plindex.pl for this.  Fixed a few typos.


VERSION 2.9.5
=============

  * FIXED: dwim_predicate to deal properly with default modules.

  * FIXED online manual not to use overstrike by default.  See manual
    for details.  XPCE requires patched prolog/lib/swi_help.pl to work
    properly with this version.

  * FIXED: plld for handling -l<lib> correctly in the Unix version, and
    automatically deleting temporary .exp files in Win32.

  * FIXED important fix returning address of local variable, found by
    Jean Daniel Fekete.  Thanks.


VERSION 2.9.4
=============

  * FIXED: Various references to the variable stacks for systems requiring
    the stack-shifter.  Thanks to Michirou Yabuki for reporting.

  * FIXED: recorded database (and findall/3, bagof/3, setof/3 store) 
    handling of strings.  After retrieval, the string's indirect header
    was incorrect, making unification and equivalence fail.  Thanks to
    Andrew Dadakow for providing me with a simple program illustrating
    the problem.

VERSION 2.9.3
=============

  * ADDED: (Simple) support for exceptions in the GUI-tracer.

  * MODIFIED: PL_extensions array now needs to be explicitely registered
    using PL_register_extensions() for compatibility with Win32.  Documented
    PL_register_extensions().

  * FIXED: print/1 to include the `quoted' option as it used to before
    2.9.0.  Thanks to Sam Waugh for noting.

  * NEW: plld is now written in C, and adapted for usage on Windows-NT
    and Windows '95.  The latter is incomplete, but useful for creating
    embedded Win32 console applications.  The old plld is available as
    plld.sh in the source distribution.

  * FIXED: PL_register_foreign() now declares the function-pointer as
    a void * for C++ code, so it may be used with C++.

  * MODIFIED: tmp_file/2 now returns the canonical filename on
    Windows platforms (i.e. c:/temp/base<n>, rather then C:\TEMP\base<n>).
    use prolog_to_os_filename/2 to convert between the two formats.

  * FIXED: catch/3 for proper continuation if the recovery goal
    succeeds.

  * FIXED: definition of ulong on some platforms for the new pl-global.h
    module.


VERSION 2.9.2
=============

  * CLEANUP: Removed various unreachable statements reported by the
    SGI native compiler.

  * FIXED: Unresolved message for S__fupdatefilepos() using native
    SGI compiler, which does not emit code for inline functions.

  * FIXED: diagnosis of `discontiguous' and `redefined' predicates
    while the predicate is reconsulted while it is running.
	
  * FIXED: Posibility of calling alloca(0) in pl-rec.c, spotted by
    Tamas Laufer.  Should fix SCO Unix version.

  * FIXED: absolute_file_name/3, generation of multiple solutions:
    avoid regenerating the same solution.  Caused make/0 to slow down
    more and more.

  * IMPLEMENTATION: Partial preparation for multi-threading.  Removed
    lots of unnecessary global variables and moved most of the remaining
    ones into three structures defined in the new file pl-global.h.
    Read-only global data is now declared `const', putting it into
    shared memory on good machines/compilers.  As a result, SWI-Prolog
    is a little smaller and faster.

    Still need to get rid of the remaining global variables and need
    to embrace all heap-operations to prepare them for the use with
    mutexes.

  * FIXED: trace-interception calling on fail-port, causing the GUI
    tracer to crash on some ocasions.

  * DELETED: Source file pl-dump.c, implementing save/1, restore/1
    and save_program/1.  These predicates only worked on a few
    platforms anyway.  qsave_program is now the only (and portable)
    saved-state mechanism.

  * IMPROVED: Removed limit on number of user-defined arithmetic
    functions.

  * IMPROVED: Format ~s accepts both a list of ASCII chars or a
    string (see string/1) object.  Thanks to Peter Ludeman.


VERSION 2.9.1
=============

  * FIXED: auto-detection of -export-dynamic in favour of -rdynamic
    (GNU-ld based systems using ELF binary format not supporting
    -rdynamic, e.g. Solaris using gcc with GNU-ld).  Thanks to
    Volker Weber.

  * FIXED: mmap configuration issues, with thanks to Daniel Pun.

  * FIXED: some changes to the Makefile(.in) and configure for portability,
    by Joel Faedi.

  * FIXED: wouldBindProcedure(), used by $xr_member, used by the explain
    facility.  Could crash.


VERSION 2.9.0
=============

  * ADDED/MODIFIED: The interface to PL_open_query() has changed.
    The debug argument is replaced by a bitwise or'ed flags argument.
    The values FALSE and TRUE have their familiar meaning, making old
    code using these constants compatible. Non-zero values other than
    TRUE (1) will be interpreted different.

  * DELETED: display/[1,2] and displayq/[1,2].  Added emulation into
    library(backcomp).

  * ADDED: ISO/Quintus compliant write_canonical/[1,2].

  * FIXED: recorded database bug for very large terms.

  * ADDED: Lots of exception codes.  Roughly, file i/o, external program
    invocation and arithmetic now use exceptions.

  * IMPROVED: write/1 and friends now check the return code of the
    low-level I/O functions and fail with exception on read/write
    errors.

  * REMOVED: $print/2.  Doesn't appear to be used anywhere.

  * ADDED: write_term/[2,3], ISO compliant

  * ADDED: ISO compliant exception handling using catch/3 and throw/1,
    including a C-interface for these (PL_throw() and PL_exception())
    Added exception port to the tracer.

  * ADDED: abolish/1, ISO compliant.

  * FIXED: A is "a" (list as abbreviation for a character).


VERSION 2.8.7
=============

  * FIXED: require/1 to be silent on already defined system predicates.

  * FIXED: passing ldflags in plld script.

  * CONFIG: Removed checking for -lelf if the system is not asked
    to configure old save/1.

  * CONFIG: Modified test/mmap.c to find out whether we should allocate
    from the top or base of the heap.  Added TOPOFHEAP to config.h.  Should
    fix Irix problems.


VERSION 2.8.6
=============

  * Included src/pl.1.in (new file, forgotten in the 2.8.5 release)
 
  * INSTALL: slightly more careful installation of the manpages and
    small problem in configure fixed.


VERSION 2.8.5
=============

  * MAN: Updated manual sources for a couple of recent changes, added
    support for generation of the help/1 database using new tools for
    nroff like generation of plain text from a LaTeX document.  Generated
    all three formats of the manual: HTML, PostScript and plain text.
 
  * FIXED: Installation of the manual page for correct description of the
    pl -dump-runtime-variables.

  * ADDED: For machines using memory-mapped stacks (Linux, SunOs, Solaris,
    OSF/1 for example), added heap-size switch: -H.  Default is 256Mbytes.

    Size switch now take optional 'm' (Mega), 'k' (Kilo, default) or 'b'
    (bytes): -L32m specifies 32 Mbytes local stack.

  * FIXED: print error message if heap allocation above prefect fit
    schema (>1024 bytes) fails (malloc() returns NULL).  All allocation
    failures now call outOfCore().

VERSION 2.8.4
=============

  * FIXED: PL_{get,put,unify}_pointer() mapping of pointer to integer,
    to ensure all possible pointer values are restored properly.

  * CLEANUP: Removed various internal unused functions, changed
    functions to be local that were only called locally.
  
  * MODIFIED: Redesign of various parts of the system to get rid of
    terms living in the permanent heap. This modification allows the
    permanent heap (where malloc() operates) to grow unlimited (used to
    be 64 MB).

    + Records (recorda/3, recorded/3, erase/1) are no longer stored
      as copies of the global-terms, but instead as a form of compiled
      code, optimised for copying the object back to the runtime stacks.

      Records are also used by findall/3, setof/3 and bagof/3, and these
      predicates have thus been modified too.  The interface between the
      C and Prolog part has changed, making old saved-states worthless.
      Old QLF files work properly.

    + Records are also used by the /f goal option of the tracer.  The
      implementation of this has been changed drastically.  The result
      is a lot faster while searching and a bug has been fixed.

    + loadXRc() in pl-wic.c has been modified not to store longs, doubles
      and string onto the heap.  This is the desired behaviour anyway.

    + Feature storage changed to use a union type, rather then integers
      on the heap.

    + Variable analysis in the compiler now used TAG_ATOM|STG_GLOBAL,
      like records, to flag the analysed variables.

    + Temporary variable management in read/1 using the same trick.

    + Atoms are indexed over a global, resizable, array.

    GOOD THINGS

    + makeRef() now simply is makeRefLG().

    + Trail() is simplified a lot.

    + makePtr() (pl-gc.c) no longer deals with heap pointers

VERSION 2.8.3
=============

  * FIXED: Changed manual to talk about PL_atom_chars(), rather then
    PL_string_from_atom().

  * FIXED: oset_addel/3, thanks to Robert van Engelen for both the
    report and the patch.

  * FIXED: string_to_list(X, []).

  * FIXED: Order and unlinking shared objects.  Now, all files are
    closed before unlinking any shared libraries.  Shared libraries
    are unlinked explicitely only on non-Unix systems.


VERSION 2.8.2
=============

  * FIXED: GC/tracer for clauses holding string objects at particular
    places.  Reported by Andrew Dadakow.

  * FIXED: Deleted old pl.mak, and added plwin.mak and plcon.mak for
    rebuilding the sources on Windows.

  * FIXED: Typo in the $write_on_* predicates, underlying sformat and
    swritef, causing a crash on > 1024 characters output.  Thanks to
    Shane P. McCarron.


VERSION 2.8.1
=============

  * FIXED: DEC Alpha (64-bit): reading integers	> 2**31-1.  Configuration
    of mmap based sparse stack allocation to deal with the Alpha.  Various
    warnings removed.  Fixed test.pl to be aware of the Alpha where
    necessary (float-3 test).

  * FIXED: Garbage collection problem, occurring with a specific
    combination of call-back from C and choicepoint organisation
    in the callback environment.

  * FIXED: Tracer `retry <n>' (guitracer only) to take care of garbage
    collected choicepoints.

  * FIXED: initialisation of style_check defaults to specify
    singletons, long atoms and discontiguous clauses.  NOTE: THIS MAY
    CAUSE WARNINGS ON OLD CODE.

  * ADDED: Several predicates for math in library(quintus).

  * FIXED: abolish/2 on active (running) predicates, not to remove the
    NEEDSCLAUSE_GC flag, so the clauses are actually removed if the
    predicates is finished.  Thanks to Paulo Moura, author of LogTalk.

  * FIXED: PL_get_arg() when using -L0 -G0 (maximized stacks).  Probably
    only breaks tracing code under these circumstances.


VERSION 2.8.0
=============

  * FIXED: `$qlf_info'/3 (always failed).  Used by the development
    environment under construction.

  * RUNTIME SYSTEM: Made various of the debugger options conditional
    on whether or not the system is compiled as runtime system.

  * ADDED: more options to user:prolog_event_hook/1 for better
    interaction	with the GUI tracer: possibility to `watch' a
    stack-frames end-of-lifetime.

  * FIXED: writeq('%') to write '%' rather then just %.

  * FIXED/MODIFIED: subterm_positions option of read to return the
    positions of possible surrounding braces for a term.  Thus,
    reading (hello) now yields 0-6 rather then 1-5.  This notably
    fixes the 'f' (finish) option in the GUI tracer to properly
    indicate the succeeded clause.

  * PORT: Configure detected tcgetattr()/tcsetattr() usage rather then
    ioctl(), fixing terminal interaction on OSF/1.

  * PORT: Fix in Makefile to make it work with some broken shells.

  * PORT: renamed I_POP virtual machine instruction to I_POPF, to avoid
    a conflict with system headers on some machines.

  * PORT: Added support for the 64-bit DEC Alpha processor (or, more
    in general made the code 64-bit clean).  Tested on a DEC Alpha
    using OSF/1 4.0 and the native C-compiler.  Should also work on
    GCC, but the local GCC installation appeared broken.  With thanks
    to Bryan Sorrows for providing me with access to their machine.
    Exactly while I was working on the port, Martin Ostermann mailed
    me patches for running on the Alpha under Linux.  Thanks for the
    couple of problems I missed!

    Remaining problems: can sparse memory management work on OSF/1?
    Currently, saved states are portable, but the limits on the Alpha
    are much larger.  This should be fixed.  Prolog machine words are
    64 bits on the Alpha, doubling the stack-sizes and virtually
    removing all limits.  In theory, it would also be possible to use
    ints (32-bit) for this.  I have not checked this.  It is not unlikely
    there are variables defined `int', where they should have been
    `long', truncating large numbers.

  * FIXED: globalAlloc() for allocations larger than a page on machines
    with sparse memory management, not handling stack-overflows as
    exceptions (Win32).  Fixes handling of long string objects on these
    platforms.

  * FIXED: (GUI Tracer) Stopped `cut-port' from activating when in
    `leap' mode.


VERSION 2.7.20
==============

  * ADDED: Documentation for expand_query/4 and expand_answer/2.

  * ADDED: call_with_depth_limit/3, to aid theorem provers.

  * ADDED: features 'unix' and 'windows' for these operating systems. 

Version 2.7.19
==============

  * FIXED: functor(X, name, -1), reported by Robert van Engelen.  Thanks.
	
  * FIXED: :- format_predicate/2 handling of arguments.

  * ADDED: external "C" declaractions for SWI-Stream.h, so you can use this
    in C++ programs now.

  * FIXED: the function sign/1 for floating point numbers.

Version 2.7.18
==============

  * ADDED: Directory html for a SWI-Prolog based latex2html translator.
    Very extensive example of using foreign code.

  * REMOVED: Lots of unused files from the source-distribution

  * WIN32: Removed the uxnt.dll library.  This library is now a static
    library linked into libpl.lib, the SWI-Prolog kernel.

  * FIXED: Handling of -p alias=path:...: order of the arguments doesn't
    matter anymore and parsing of the path has been fixed.

  * MODIFIED: load_files/2, `silent' option inherits to loads triggerred
    from this one.

  * FIXED: Garbage collector error, causing a crash if the local
    and global stack together exceed 64 MB.  Now, they can each
    be 64 MB and be allocated at arbitrary positions.

  * CHANGED: Default editor command is now <editor> "<file>", using
    double instead of single quotes.  This fixes problems on Windows
    platforms.

  * ADDED: clause_property(+Ref, ?erased), to support the debugger
    reporting about running modified clauses.

  * FIXED: current_functor(+Name, +Arity).  Reported by Stefan Wimmel.
    Thanks.

Version 2.7.17
==============

  * MODIFIED: the `debug' argument to PL_open_query() now really stops
    the debugger operating inside the called goal, also if an error
    arrises.

  * PORT: Sgi/Irix headers configuration and detection of alignment
    restrictions on doubles.

  * FIXED: Better operator priority checking, making a :- b :- c illegal
    syntax, as it should be.  Also improved the warning issued.

  * FIXED:  Removes MAX_TERM_NESTING from read.pl, previously limiting
    the complexity of terms that could be read.  The new version of
    read requires significantly less (C-) stack and can handle
    much more deeply nested terms.

  * FIXED: term_to_atom(+Term, -Atom) on machines with dynamic stacks,
    but no exception based expansion (PC version).

  * FIXED: Sopenmen() stream functions (was not used before).  This
    is now used by tellString() and toldString(), who now have a
    different interface.  These functions are used by term_to_atom/2,
    and format/[1-3].


Version 2.7.16
==============

  * FIXED: Various minor issues in the Makefiles and configure for
    generating a runtime version.  Error message if the runtime
    system cannot find its state.

  * FIXED: Heuristics for making hash-index.

Version 2.7.15
==============

  * FIXED: Embedding: the kernel now not longer gives up if it cannot
    find the Prolog home directory.  feature(home, Home) will fail if
    the home could not be located.

  * FIXED: Configure problems related to -l[n]curses, etc.

  * FIXED: retractall(Module:Head(+Arg, ...)) (i.e. explicit module and
    instantiated first argument).

  * ADDED: atom_prefix(+Atom, +Prefix): test of Prefix is a prefix
    of Atom.

  * FIXED: Bug in Unify between non-tagged and tagged integer.

  * FIXED: Bugs in configure, both improper test of double alignment
    and improper testing for the cursus libraries.  Thanks to
    Masafumi Nakane.

  * IMPROVED: Moved source_file/2 to foreign language to exploit the
    kernel-maintained database for enumerating the predicates loaded
    from a sourcefile.

  * MODIFIED: prolog_trace_interception/3 now has 4 arguments.

  * ADDED: Support for tracing the cut in the source-level debugger.

  * ADDED: Support for `break-points' to the debugger.

  * FIXED: Protocol to include the prompt in the protocol.

  * ADDED: clause_property(ClauseRef, fact).  Used by source-level tracer.

  * ADDED: Various options to prolog_frame_attribute/3 for the source-level
    tracer.

  * FIXED: allow for tracing the unify-port of a fact.

  * ADDED: prolog_frame_attribute(Frame, argument(N), Arg) to read
    bindings from a stack-frame.

  * ADDED: Various options to plld, the standalone executable linker.

  * IMPROVED: (if->then;else) to generate tail-recursion code for the
    `then' part.

  * ADDED: $clause_position/3 and prolog_frame_attribute(Frame, pc, PC).
    First steps for a source-code debugger.

  * IMPROVED: Clause-representation to delete subclauses member, which
    proved obsolete using the current system.  Added UNIT_CLAUSE flag
    to the clause's flags to achieve the same support for the decompiler.

  * FIXED: handling of the stream user_error by other predicates than
    format/[1-3].  Also, using output from write/2, etc. to unbuffered
    streams like user_error is now buffered in 256 byte-blocks, but
    guaranteed to be flushed after the write operation completes,
    resulting in fewer calls to write() and therefore generally better
    performance.

Version 2.7.14
==============

  * FIXED: Win32 shell/1 implementation has changed radically, not
    using threads anymore.  This hopefully fixes shell/1 on all
    platforms.  The old version started a thread to wait for the
    process, while the main thread continued processing windows
    messages.  The new version loops through PeekMessage, GetExitCodeProcess
    and Sleep, processing messages and waiting in the same (main)
    thread.

  * FIXED: reentrance problem in Sgetc() (low level fetch for character),
    upsetting the tracer sometimes when using XPCE.

<this version was put on the ftp server Sep  6>

  * FIXED: current_stream/3 failed to properly enumerate the streams.
    Thanks to Robert van Engelen.

  * MODIFIED: ensure_loaded and use_module now load if the file has
    been changed since it was last loaded, and not only if it was not
    loaded before.

  * ADDED: load_files/2 to load files with various options (including
    silent loading).  The undocumented $consult_file/2 has gone!

  * INSTALL: Win32: nice looking installation procedure, based on the
    WISE installation expert package.

  * ADDED: A *-> B ; C (softcut).

  * FIXED: Random generation for machines that use rand().  Still
    poor, but then this function is bad.  Maybe use our own someday.

  * ADDED: Win32: console support for variable-pitch fonts and user
    selection of fonts.

  * FIXED: <String> =.. X, found by Robert van Engelen.
	
Version 2.7.13
==============

  * FIXED: prolog_frame_attribute/3 to include the arguments in the
    goal.  Found by Andreas Schlemminger.

  * FIXED: listing (clause/2) for predicates holding if->then;else or
    a;b in their body.  Found by Andreas Schlemminger.

  * FIXED: shell/1 for Windows platforms (waited almost indefinitely
    before executing the program).

  * ADDED: plregtry.dll and registry.dll, providing access to the
    Win32 registry database.  

  * ADDED: setting up a DDE server for better interaction with the
    Windows 95 shell (direct edit and consult from the explorer).

Version 2.7.13 (ALPHA)
======================

  * ADDED: mode update for open/[3,4] to write at any location in an
    existing file. 

Version 2.7.12
==============

  * FIXED: behaviour of the tracer.  Notably included missing fail-ports
    from the trace.  Also fixed the box-counts for the profiler.

  * ADDED: expand_term/2 now first tries term_expansion/2 in the module
    that is being loaded.  After that it tries the module user.

  * FIXED: Various improvements to the explain facility, notably much
    better location of predicate cross-references.

Version 2.7.11
==============

  * MODIFIED: feature(version, Version) and PLVERSION are now numeric.

  * FIXED: reporting out-of-stack now never calls the Prolog exception
    handler to avoid a real crash.

  * ADDED: Syntax for maintaining source-location inside term-expansion.
    If a term of the form $source_location(File, Line):Clause is found,
    not the current, but the given location will be recorded with the
    clause)

Version 2.7.10
==============

  * PORT: More changes to PL_unify_term() by Franklin Chen.  Now really
    compiles on MkLinux.

  * FIXED: retract/1 once more.  Now tested on all combinations of
    (non-)unit-clause and with(out) module specifier.

Version 2.7.9
=============

  * FIXED: interaction between tracer and garbage-collector, sometimes
    causing an assertion-failure in the garbage collector when tracing.
    Reported by Lourens van der Meij.

  * CHANGED: flag/3 now handles full 32-bit integers and double
    float values.  Old version was limited to tagged ints and didn't
    do floats.

  * PORT: Rewrote PL_unify_term() to avoid using va_list *.  May or
    may not help.  Problem arises on the PowerMac version of Linux
    when compiling pl-fli.c.  Reported by Franklin Chen.

  * PORT: Portability patches for AIX 3.2/4.1: avoid name-clash with
    hz and fid_t.  Contributed by Kay Roemer.

  * FIXED: documentation of PL_unify_list() interface function.

  * FIXED: name/2 to behave correctly in the tracer.  This problem
    may appear with more foreign predicates and maybe requires a
    more fundamental solution.  Reported by Chan Kam Fai.
	
  * FIXED: retract/1 on non-unit-clauses.  Thanks to Liviu Badea.

Version 2.7.8
=============

  * Some fixes to the Makefile.  No functional change.

Version 2.7.7
=============

  * DOC: Added documentation for PL_unify_term(), making its specs
    `official'.

  * ADDED: PL_query(PL_QUERY_VERSION) to find the version of Prolog
    running.  Used by plwin.exe to display the correct version in the
    window titlebar.

  * WIN32 Process creation: added win_exec/2 and changed shell/1 such
    that shell('<Command> &') behaves as win_exec(<Command>, normal).

  * WIN32 DDE: Added dde_poke/[3,4] to support DDE poke operation required to
    communicate with the sybase database for Windows.  MODIFIED
    dde_request/3 to return a string object rather then an atom to
    avoid filling the atom-space.

  * WIN32: For filenames, ~ is expanded to %home%.  When not present,
    %homedrive%%homepath% is used, which expands to NT's notion of the
    home directory.  Finally, '/' is used as fallback.

  * MODIFIED: Changed directory structure of make rt-install to be
    the same as normal installation.

  * FIXED: Installation on Pentium Pro: bad detection of canonical
    system type by autoconf's config.sub.  Updated configure.in to
    use autoconf 2.10.

  * FIXED: Backtracking on floats and large integers appearing in the head.
    The VM instructions H_FLOAT and H_INTEGERS handling these didn't
    trail the argument.  Bug introduced in 2.7.0.  Thanks to Peter
    Terptra for reporting.

Version 2.7.6
=============

  * MODIFIED: Added some more support for very deeply nested terms on
    the last arguments (long lists beeing one of them) by introducing
    a new compilation schema for such terms.  Also modified numbervars/4
    to exploit right-recursion of terms.

  * MODIFIED: Argument-stack default-limit changed from 8 KB to 1 MB
    for machines with dynamic stacks.  16 KB for others.  This limits
    most of all the depth of terms handled by assert/retract.

  * FIXED: Emacs-interaction bug using history.  Thanks to Dave Moffat.

  * FIXED: decompilation (retract, listing, etc.) for predicates with
    0 arguments.  Reported by Dave Moffat.

  * FIXED: configuration for system where readline requires -lcurses
    rather then -ltermcap (and the latter is not present).

Version 2.7.5
=============

  * FIXED: typo in float <-> long conversion problem.

  * FIXED: plld now passes -D* to the compiler rather then the linker.

Version 2.7.4
=============

  * FIXED: handling of floating-point conversion to integers on machines
    raising SIGPFE on l = (long)f when f is out of the long range.  Thanks
    to Sven.Hader@Informatik.TU-Chemnitz.DE (Sven Hader).  The problem
    appears at least on Linux running on a Pentium.

  * MODIFIED: Added -F file flag to select from multiple initialisation
    scripts, just like -f file.  Old versions only loaded plrc.   The
    new version by default loads <program>.rc.  -F none stops loading
    this file.

  * FIXED: plld: gave error code 1 (always).  Added various flags: -v
    -help, -pl.  Updated manuals

  * FIXED: PL_next_solution() detection of non-deterministic success
    (reported deterministic for actually non-deterministic goals).

  * ADDED: For XPCE users: nice graphical frontend for the online help
    functions.  Working on much better Prolog mode for PceEmacs.

  * PORTABILITY: Removed void * arithmetic in pl-setup.c, removed
    a couple of other non-strict-ansi things there.  Added configure
    for alloca().  Reported to compile using IRIX 5.3 native compiler
    now.

  * FIXED: Sclose() flushed write-buffer for read-only streams.

  * ADDED: read_term/[2,3]: reading with various options

  * FIXED: copy_term/2: handling of combination of ground compound
    terms and shared variables.

  * FIXED: PL_next_solution() detection of determistic success.

  * ADDED: concat_atom/3 for concatenating multiple atoms with a separator.

  * FIXED: Online manual generation for dynamic/1 and friends.  Parser
    now deletes \verb from summaries.

  * FIXED: $xr_member (underlying explain/[1,2]) for clauses containing
    string objects (crashed).  Improved various details to explain/[1,2]

  * MODIFIED: Quoted writing of an invalid float yields '$Infinity' or '$NaN',
    unquoted Infinity or NaN.

Version 2.7.3
=============

  * FIXED: ?- expand_term(A,B), reported by Fergus Henderson.

  * FIXED: cleanup after calling Prolog-defined arithmetic functions
    (caused a crash when two arithmetic functions are called in the
    same context).

  * Renamed PL_reinit_hook() to PL_initialise_hook(), which reflects
    more the current function.  Use this to register the readline
    interface, so it is available while loading .plrc.  Se also
    pl-extend.c and its public copy stub.c.

Version 2.7.2
=============

  * ADDED: features `debug_on_error' and `report_error'

  * ISO: If a predicate has no clauses and is defined either dynamic,
    multifile or discontiguous, it is considered defined.  This used to
    hold only for dynamic predicates. 

Version 2.7.1
=============

  * FIXED: Signal/readline/abort interfaces for the Win32 versions, so
    signals are handled correctly again and readline-based input handling
    works.

  * FIXED: bug in setup of memory-base pointers, causing all versions
    to fail who allocate memory higher than 128MB, which includes the
    win32 version under win32s (Windows 3.1)

  * FIXED: ar/ranlib configuration (notably for BSD systems, such as
    SunOs 4.1).

  * FIXED: do not load readline interface if the input is not a terminal.
    This bug prevented constructs in shell-scripts such as pl << _EOS_ ...

Version 2.7.0
=============

  * FIXED: HPUX compilation thanks to Gordon Streeter.

  * WIN32: The kernel is now in libpl.dll, which comes with two toplevel
    drivers: plcon.exe for a standard IO version and plwin.exe for the
    windows based version.  New directory embed with the sources of
    both toplevels.

  * FIXED: memory leak after assert/retract of code holding floats,
    32-bit integers or strings (not lists of char-codes).  Also
    provides more compact code for floats and large integers
    (both small and large integers require 2 words, doubles 3 words).

  * IMPROVED: More compact representation of compiled floats, long
    integers and strings.

  * MODIFIED: Complete rewrite of the internal datastructures.  The
    aim is to avoid mixing pointers and unsigned longs on the stacks
    and thus remove the various assumptions on the memory model underlying
    the prior versions. See pl-data.h for details.

  * IMPROVED: Lifted the maximum number of variables in a clause from
    256 to 65536, maximum arity of predicates from 128 to 1024.  Both
    numbers are fairly arbitrary and can be raised further at the cost
    of wasting a little more memory.

Version 2.6.0
=============

  * ADDED: plld and manpage for creating embedded executables.

  * FIXED: flush output of terminal streams while halting.

  * ADDED: option stand_alone for qsave_program to create stand-alone
    executables!

  * INSTALL: The executables are now installed in $(PLBASE)/bin/$(ARCH),
    i.e. using a different directory for each platform, so multiple
    platforms are supported more easily.

  * MODIFIED: Drastic reorganisation of arithmetic handling:

	- All arithmetic is now handled using 32-bit longs and 64-bit
          doubles.

	- Smaller integers (within the range described by the features
	  min_tagged_integer ... max_tagged_integer) are represented
	  internally as tagged integers.  Larger integers and doubles
	  are represented as `indirect data'.

	- A generic representation for `indirect', covering uniform
	  handling of them by the virtual machine, unify and garbage
	  collector.  This deals with strings, doubles and `bignums'.

	- New interface between the arithmetic functions and the
	  arithmetic predicates (is/2, >/2, etc.) as well as their
	  virtual machine instructions.  This new interface is faster.
	  and avoids unnecessary type-conversions.

	- Augmented/renumbered the virtual machine instructions, making
	  old saved states worthless.

	- Fixed a couple of functions translating between floats and
	  integers: integer/1, ceil/1, floor/1, float_integer_part/1,
	  truncate/1, etc. for handling large numbers correctly.

	- Added the feature float_format to define how floats are
	  printed by write/1, print/1, etc.

  * MODIFIED: Disconnected readline and Win32 I/O window interface to
    a separate module.  This is a necessary precondition to arrive at
    a modular and embedible Prolog engine for Win32.  See pl-rl.c

  * FIXED: unknown/2 (reporting instantiation fault).

Version 2.5.6
=============
  
  * FIXED: ceil/1, floor/1 and integer/1 to handle large floating point
    numbers correctly.

  * MODIFIED: write and friends to print floating point numbers using
    the `%g' format by default, printing large floats as -for example-
    3e20.  Use format with the ~f option to format floats as you please.

  * FIXED: on some machines <assert.h> requires <stdio.h> to be included.
    configure now checks for this.

  * FIXED: .qlf file-magic verification.

  * FIXED: Some minor portability problems: test for CC supporting -c -o
    combination, solaris prototypes for random and srandom added, changed
    system parameter detection for file-table-size and page-size to use
    sysconf() when available.  Compilation is now silent on solaris 2.5,
    except for a number of `might not be initialised' warnings in pl-wam.c
    that aren't correct (also, these are not reported by other versions
    of gcc).

Version 2.5.5
=============

  * FIXED: Important bug in =@=, also used by bagof/setof, leading to
    crashes on some structures and failure on structural equal terms
    on others.

  * FIXED: Crash in the tracer under some circumstances, reported
    by Michael Schulz.  

  * FIXED: loading Quick Load Files that do not contain modules.

Version 2.5.4
=============

  * FIXED: read/1 for reading negative floating point numbers (2.5.x bug),
    thanks to Bill Jones.

  * FIXED: read/1, etc. for reading a single variable.  Found by Luu Tran.

  * FIXED: DCG expansion error found by Keith Whitwell.


Version 2.5.3
=============

  * ADDED: ISO at_end_of_stream/[0,1] and peek_byte/[1,2].

  * Fixed and faster nth0/3 and nth1/3 implementations by Martin Jansche.

  * New pl(1) manual page by Martin Jansche.  Thanks.

  * PORT: Ron Ferguson mailed me a couple of fixes for the NeXT machine,
    using release 2 of the C-compiler from the standard development system.
    Thanks.

  * FIXED: decompilation (listing, retract, etc.) for clauses using the
    new (2.5.x) A_REAL instruction.

  * FIXED: \=/2 and recorded/3 for handling shared variables.  Found
    by Joerg Garbers.

  * ADDED: edit definition for emacsclient(1).

  * Fixed unify (=/2) for unification of two floats.  Reported by Dave
    Moffat.

Version 2.5.2
=============

  * FIXED: PL_retry() and friends were lacking from the new SWI-Prolog.h

  * FIXED: PL_cons_functor() and PL_cons_list(), also fixing variable
    handling in bagof/setof.  Thanks to Khanh Doan for reporting.

  * ADDED: string_concat/3 with same semantics as concat/3, but unbound
    will be unified with a string object.

  * ADDED: rl_read_init_file(+File) and rl_add_history(+Line) for better
    readline interaction.  Added readline.3 to the standard installed
    manual set.

  * ADDED: file_name_extension/3 to reason about filename extensions in
    a machine-independent manner.  Fixes Win32 associations if the filename
    has uppercase extension.

Version 2.5.1 (released for Win32 only)
=======================================

  * FIXED: Stack expansion for some foreign predicates using the local
    stack as temporary area for machines with exception-based stack-overflow
    handling that do not provide the address of the segmentation fault to
    the handler (Win32, Linux).

  * FIXED: Linux: repeated handling of the sequence Control-C, abort.

  * FIXED: Crash after the system has ran out of some stacks on machines
    with exception-based stack-overflow handling and POSIX signals.
    Solaris, Linux and Win32 are the examples I know of.

  * FIXED: CVT_NUMBER and CVT_ATOMIC constants in SWI-Prolog.h,
    breaking name(+Float, -Chars).

  * FIXED: plus/3 for +, -, + instantiation (2.5.0 introduced typo).

  * FIXED: prototype declaraction reported by Martin Jansche.

Version 2.5.0
=============

  * Added features `trace_gc' and `gc'.

  * Added `pl -arch' to get the architecture identifier easily for
    installation and makefiles

  * New implementation of copy_term/2 that shares common compound
    sub-terms.

  * Totally new foreign language interface using `term-references' to
    allow for garbage collection and stack-shifts with active foreign
    code.  Ported all foreign predicates to the new interface.  This
    interface also allows for generating multiple alternatives for
    a Prolog goal from C.

    For compatibility with old foreign code, see README.oldforeign.

  * FIXED: optimised compilation of A is X (i.e. second argument is
    a variable).

  * COMPILER: improved compilation of floating-point arithmetic using
    -O (optimised), avoiding unnecessary copying of floating point
    numbers to the global stack.

****************************************************************
	     INCOMPATIBLE FOREIGN LANGUAGE INTERFACE
****************************************************************

Version 2.1.15
==============

  * FIXED: read/1 to push the load context when reading end-of-file, so
    the following works:

	term_expansion(end_of_file, end_of_file) :-
	    	prolog_load_context(file, Path),
		format('Finished loading ~w~n', [Path]).

  * FIXED: abolish/2 on imported procedures.  Reported by Peter Barth.

Version 2.1.14
==============

  * DISTRIBUTION: Removed various out-of-date files from the distribution:
    Makefile.win, Makefile.dos, etc.

  * WIN32S: Fixed problem in the garbage collector.

  * WIN32: Improved cputime for NT ('95 and win32s use the old code).

  * MANUAL: Martin Jansche <martin@pc03.idf.uni-heidelberg.de> has send me
    patches for the manual, fixing many smaller and bigger mistakes in it.
    Thanks!

  * DEBUG: Added stuff for debugging for different memory models on Unix
    machines with an mmap() that can map memory at the addresses normally
    used by the target machine.  See morecore.c

Version 2.1.13
==============

  * WIN32: Fixed error reporting of shell/1.

  * FIXED: added a flush() after completing the user-query.  This gives
    better output for ?- write(hello).

  * FIXED: file-name conversion cache management.  This cache is used
    by absolute_file_name/3.

Version 2.1.12
==============

  * Most of these fixed after comments from David Plummer.  Thanks.

  * FIXED: displayq for ','(...)

  * FIXED: read/1 and friends to handle {}(..) and [](...) correctly.

  * FIXED: format/[2,3] to be able to write unlimited-length output,
    provided there are no `pending' ~t's.

  * COMPAT: absolute_file/3 to accept list of access-modes

  * MODIFIED: access_file/2 to succeed on write and append mode if the
    file does not exist, but the directory can be written.

  * FIXED: unification order in translating grammar --> {goal}.  Noted
    by Andreas Steiner.

  * FIXED: Temporary-buffer management in Svfprintf() and friends.

Version 2.1.11
==============

  * FIXED: functor(X, 8, 0) to yield X = 8.

  * DELETED: library_directory(.).  Gives too much problems because the
    system picks wrong files or directories.

Version 2.1.10
==============

  * ISO: added compliant open/4 predicate.

  * Moved all printing of the system (banner, prompt and warnings to
    use user_error (=stderr) rather than user_output (=stdout), so
    it becomes easier to use Prolog's standard output.  Stderr is
    unbuffered, several predicates that will output more than one
    character now use a `temporary buffer' to reduce IO-load.

  * ISO: Added arithmetic functions: rem/2, ** (= ^), ceiling (= ceil),
    float/1, float_fractional_part/1, float_integer_part/1, truncate/1,
    sign/1 and round/1 (= integer/1).

  * ISO Syntax: Changed quoted atom and string syntax to support character
    escapes, broken lines, etc.  These changes can be switched off
    using ?- set_feature(character_escapes, false). for backward
    compatibility.

    Also, 0b110, 0xa2 and 0o70 (binary, hexadecimal and octal) number
    representations are now recognised.

  * ISO: Added features bounded, integer_rounding_function, max_arity.

  * WIN32: Various changes to the console: use standard colours and
    font, allow for changing colours.  Bind Control-Z to end-of-file
    (alternative for Control-D, which is still valid).

  * WIN32: `pl state.qlx' now assumes state.qlx is the result of a
    qsave_program/[1,2] and automatically loads the state.  This
    allows for associating states with the emulator.  Also, pl file.pl
    will automatically chdir/1 to the directory containing the file
    and load the file before entering the toplevel.

  * WIN32: Fixed some filename case problems: expand_file_name/2 now
    works case-insensitive.  Comparing files for sorting is done case
    insenstive.

  * WIN32: Command-line breaking now handles "quoted arguments".  Only
    double quotes and no escape (I don't know the Windows'95 escape
    conventions).

  * WIN32: Fixed filename completion from console window.

  * INSTALL: Fixed detection of non-gnu/gnu make

  * FIXED: use_module/1, etc. to import predicates exported using the
    export/1 directive instead of the module/2 directive.

Version 2.1.9
=============

  * FIXED: Updated stack-shifter code for the changed layout of the
    environment-stack frames.  This bug prevented pl-gc.c to compile
    on machines having no virtual-memory based stack allocation.

Version 2.1.8
=============

  * ADDED: check in exit code that removes possibly incomplete .qlf and
    bootfiles if an error occurred while building the file.

  * FIXED: WIN32 tmp_file/2.  This fixes help/1.

  * FIXED: configure for users of a shell that doesn't export $PWD and
    the system chooses the install-sh script.

Version 2.1.7
=============

  * FIXED: management of clause index-table.  Old code lead to indefinite
    growing of these tables with repetative assert/retract

  * ADDED: Improved dirty-management on clause indexing system to improve
    the performance on retract from hashed dynamic predicates.

  * ADDED: absolute_file_name/3: options file_type, file_errors and
    solutions for compatibility.

  * Win32: compiled (with small updates) for Win32

  * ADDED: Implemented open_null_stream/1 by defining a null-stream in
    SWI-Prologs stream-i/o package to avoid the /dev/null dependency.

  * ADDED: Saving current operator declarations with qsave_program/[1,2].

  * FIXED: Garbage-collector error.

  * FIXED: predicate-reference count problem
  
  * ADDED: style_check(+dynamic) to report on manipulation of predicates
    that are active in the interpreter.

Version 2.1.6
=============

  * INSTALL: installs pl in the SWI-Prolog tree and just creates a link
    from the binary directory.  Makes it easier to move and redistribute
    the SWI-Prolog binaries.

  * CHPL.c: fixed conflict for basename()
  
  * FIXED: file-searching cache returning alternate answers in different
    order.

Version 2.1.5
=============

  * ADDED: notrace(+Goal) to run Goal invisible to the debugger.

  * ADDED: open_shared_object/3 to be able to pass flags to dlopen().

  * CLAUSE INDEXING: version 2.1.5 provides hashing to speed up first
    argument indexing.  Numerous changes had to be made to realise this:
    Indirection in the clause chain of predicates, implementation of a
    lazy automatic system to guess the proper way to index a predicate,
    a new clause-reference count system (avoiding problems with manipulation
    of `active' predicates.  The representation of predicate and clauses
    has changed in various ways.

  * INSTALL: Changed various things to the configure options and detection,
    to the defaults make more sence.  Upgraded to autoconf 2.4, fixed for
    cross-compilation.

  * PORT: Fixed various things for the Linux/ELF port.  Tested on
    Linux 1.2.13 running libc-5.0.9.  Compiled with gcc-2.7.0.

  * PERFORMANCE: Implemented automatic rehashing of all (previously)
    fixed-size hash-tables.  Prevents performance degradation on very
    large programs.

  * FIXED: profile/3 problem (leading to crashes).

  * FIXED: pl -O bug: trailing of is/2 was not handled properly.

Version 2.1.4
=============

  * MODIFIED: Changed definition of absolute_file_name/2.  Moved
    absolute_file_name/3 from library(quintus) to a built-in predicate.

  * ADDED: file_directory_name/2 and file_base_name/2.

  * ADDED: end_of_file is now passed to term_expansion/2.

  * DOC: Many updates.

  * FIXED: read/1 for foo.%comment (i.e. no space between the . and the
    comment).  Note that foo./*comment*/ doesn't work as this will be
    tokenised as `foo', `./*', `comment', `*/'.

  * ADDED: lazy recomputation of clause indexing.  This notably speeds
    up loading .qlf and bootfiles.

  * ADDED: hash_term/2 for advanced indexing of databases.

  * ADDED: setting file_search_path through the command line using:
    pl -p mydir=/foo/bar.

  * FIXED: Semantics of ensure_loaded/1 if the file is already loaded,
    combined with the module system.  See ensure_loaded/1.

  * FIXED: Grammar rule compiler's handling of non-proper lists in the
    head or body (lists ending in a variable).  Lists of more then one
    element are now translated into append/3.  The following now compiles
    ok: string([H|T]) --> [H|T].

  * MODIFIED: term_to_atom/2 and atom_to_term/3 to fail silently on a
    syntax error.  Both predicates now also accept a string in the place
    of the atom to parse strings: term_to_atom(X, "foo(bar)") works as
    expected.

  * ADDED: `swi' and `foreign' aliases to file_search_path/2.

  * MODIFIED: Grammar rule translator now uses 'C'/3 instead of '$char'/3
    to extract the head.  Compatibility.

  * MODIFIED: at_initialisation/1 is now called at_initialization/1.

  * INSTALL: Fixed Makefile and configure to be able to build the system
    for multiple platforms.

  * ADDED: Infra-structure for making portable saved-states (equivalents
    of boot files):

	+ initialization/1	(goals to run at initialization)
	+ volatile/1		(predicates for which not to save clauses)
	+ require/1		(define we require this predicate)
	+ autoload/[0,1]	(autoload needed things now)
	+ qsave_program/[1,2]	(make a quick-loadable state)

  * ADDED: compound/1 to test for compound terms.

  * FIXED: compilation of ``foo:Head :- Body'' to be equivalent to
    foo:(Head :- Body).

  * FIXED: problem in read/1 and number_chars/2 that may have lead to 
    garbage collection errors.

  * FIXED: setarg/3 integrated in the trail-system.  Removes its
    choicepoint and ensures data consistency.

Version 2.1.3
=============

  * ADDED: setarg/3 for extra-logical assignment to arguments of terms.

  * MODIFIED: PL_new_integer() now returns a floating point value if the
    argument exceeds SWI-Prolog's integer range.

  * ADDED: Automatically dumps the top of the runtime stack on floating
    point exceptions.

  * FIXED: Trap floating point exceptions for the win32 version.

Version 2.1.2
=============

  * FIXED: read/1 problem.  Try reading just '0'. ...  Reported by
    Daniela Genius.

  * FIXED: `toplevel' variable expansion system, leading to various strange
    behaviours in handling queries from the user.  It now can also handle
    cases as:

    	?- X = 5.
	?- X is $X + 1.

Version 2.1.1
=============

  * MODIFIED: DCG translation of free variables now calls phrase/3, which
    has been changed slightly to deal with `un-parsing'.  Modification
    is probably not complete, but it fixes some problems encountered by
    Michael Boehlen.

  * MODIFIED: keysort/2 is now stable with regard to multiple values on
    the same key.  Makes this predicate compatible with SICStus and
    Quintus.

  * FIXED: :- dynamic, :- multifile, :- module_transparent and
    :- discontiguous to accept Module:Name/Arity, ...

  * Moved call/[1..] into the compiler.  call/[1..6] is removed from
    library(quintus) as it is now part of the base system. Also fail/0
    and true/0 are now handled by virtual machine instructions.

  * Upgrade to autoconf 2.3, fixed usage of `tr' for Solaris 2.x and
    with that the configuration of --enable-shared.

  * FIXED: number_chars/2 and name/2 now handle floating point numbers.

  * FIXED: interaction between chdir/1 and absolute_file_name/2.

  * FIXED: format('~*c', [10,45]) (or more in general, providing an argument
    to ~c to print the character multiple times).  Thanks to Michael Boehlen.

  * FIXED: PrologPrompt() to allow reading standard input from the -g and/or
    -t goal options.

Version 2.1.0
==============

  * Added facilities to allow for embedding SWI-Prolog in C applications.

  * Fixed semantics of the cut in toplevel queries by compiling the query
    instead of using meta-call.

  * Fixed bagof(A, member([B, C]), L) to yield L = [B,C] instead of making
    new variables.

  * Fixed typo in dde.pl (reported by Thiebaut Moeglin)

  * Integration of NeXT patches from Thomas Hoppe (hoppet@cs.tu-berlin.de).
    Probably still not 100% ok, but should be closer now.

  * Fixed XPCE event dispatching for pl -tty

  * PL_univg() C-interface function added for supporting XPCE > 4.8.10
    with better interface performance.

  * Fixed operator precedence problem (reported by Dave Moffat)

Version 2.0.9
=============

  * ADDED: HPUX interface for shared libraries, but a HPUX guru should
    fix the import/export details (line was too slow to browse to lots
    of manual pages).

  * FIXED: pl-incl.h typo (breaks IRIX 5.3 port and propably others)

  * FIXED: HPUX detection of mmap()'able stacks fixed.

  * FIXED: generation of include/SWI-Exports, the AIX export declaration
    file.

Version 2.0.8
=============

  * FIXED: loading shared objects using dlopen() for solaris 2.x
  
  * FIXED: shlib.pl current_foreign_library/2 administration.

Version 2.0.7
=============

  * FIXED: compilation (boot and .qlf) now donot look for compiled
    (.qlf) files.

  * CHANGED: Default goal writing the banner is now in the flag
    $banner_goal (used by XPCE as a shared library).


Version 2.0.6
=============

  * CHANGED: retractall/1 implementation is now compatible to Quintus,
    avoiding the hacky redefinition in library(quintus.pl).  The difference
    is that now the argument will only be matched against the clause-head.
    on a match the clause will be removed, regardless of its body.  Makes
    no difference for retractall on facts, but does make a difference on
    clauses with a non-just-true body.  retractall/1 is now a deterministic
    foreign predicate that no longer decompiles the clause body, making
    it faster too.

  * FIXED: made .qlf files independent of the directory they where compiled.

  * FIXED: Path canonisation problem

  * FIXED: loading .qlf files holding already-defined modules

  * ADDED: file_search_path file-location system

  * ADDED: access_file(File, exists) to check for bare existence.

  * FIXED: Another clear_uninitialised() problem related to if-then-else
    causing garbage collector and possibly stack-shift errors.  As the
    implementation is now changed radically, this problem should be gone
    forever ...

  * FIXED: copy_term/2.  Now creates more efficient terms (less references)
    and no longer creates bad references.

Version 2.0.5
=============

  * MODIFIED: Replaced libc based stream IO with more general IOSTREAM
    package.  Deleted folding capabilities as just about any IO device
    has these built-in these days.  These changes are to facilate embedding
    in window-based environments that do not support stdio.  See pl-stream.c

  * FIX: dwim_match/2 for single character mismatch.

  * ADDED: atom_chars/2, number_chars/2, atom_char/2, various new
    unix/1 arguments.

Version 2.0.4
=============

  * MODIFIED: Consult and friends (ensure_loaded, use_module, etc.)
    no longer change directory to the directory in which the file
    lives.  As a consequence, directives have to use prolog_load_context/2
    or source_location/2 to find the context directory of the directive.

    consult and related directives still load relative to the directory
    in which the currently loading file lives.

  * Added prolog_load_context/2 to provide context for directives.
    Actually moved from library(quintus) to the boot image as the
    predicate is now necessary.

  * Added -DO_RUNTIME support to make a version	that is more suitable
    for distribution of products: no profiling, no tracer, no readline
    and no interrupt handling.  Setup using configure --enable-runtime

Version 2.0.3
=============

  * Fixed: loading qlf files now push the source context while running
    a directive, so source_location/2 should work while executing a
    directive from a .qlf file.
  * Fixed: recognise MAP_ANONYMOUS for configuring mmap() based stacks.
  * Added feature(dynamic_stacks, Bool) for detection of virtual memory
    based stack management.
  * Fixed feature(open_shared_object, Bool) (Michael Kauschke)

Version 2.0.2
=============

  * Fixed pl [options] -c file ...
  * Improved VMI implementation for (if -> then ; else), \+ and (a;b).
    Reduces overhead of these to about 1/3th.
  * Added VMI support for fast calling of foreign system predicates that
    are called with only variable arguments (i.e. `test(X) :- integer(X)'
    is optimised; `test(X) :- integer(3)' is not).  Provides big speedup
    for fail, true, integer/1 (etc.), and many other commonly called
    foreign predicates.
  * Support for mmap() using MAP_ANON.  Avoids a file-descriptor and hopefully
    improves portability of dynamic stacks.
  * Fix for Solaris 2.4 mmap() detection.
  * Fix: added autoconf test for using asm("nop") in pl-wam.c or use slower
    but more portable C alternative (fixes RS/6000 version)

Version 2.0.1
=============

  * FIX in garbage collector of 2.0.0 was only half the story.  Should
    be ok now.  Thanks to Thomas Hoppe for supplying me with the error
    report.
  * FIX & performance: current_functor/2 with the first argument is
    instantiated.
  * Installation: the libraries are now installed as
    $(prefix)/lib/$(PL)-$(PLVERSION).  A possibly existing executable is moved
    from $(prefix)/bin/$(PL) to $(prefix)/bin/$(PL).old


Version 2.0.0
=============

  * Added `Quick Load File' compilation support.  See qcompile/1 and
    qload/1.  Alpha stage.
  * FIXED infrequent segmentation violation occurring on machines with
    dynamic stack management, but whose signal handler is not provided
    the address of the fault (Linux and Solaris 2 for example).  The
    crash can be in various foreign predicates that use the local stack
    as scratch area.
  * Important FIX to the garbage collector.  This bug may happen iff
    a garbage collection is invoked while clauses are active that have
    \+ or (a -> b ; c) constructs that are not yet active.  Generally
    the problem is reported as an inconsistency in the relocation count.
  * Fix to virtual machine encoding that applies to versions compiled
    with gcc 2.x and whose text-space starts at a high address.
  * Modified absolute_file_name/2 to take specifications of the
    form absolute_file_name(library('shell.pl'), X).
  * Various fixes to the new .qlf format and support for compiliation 
    of individual or combined sources into .qlf files.  .qlf files may
    now be loaded as normal sourcefiles instead of only as `boot' file.


Version 1.9.6:
==============

  * Fixed for BIG_ENDIAN machines (Intel, VAX, ...)
  * Windows version: added dde_execute/2
  * Added Quintus compatible foreign-language (C) interface.
  * Changed .qlf (former .wic) format drastically.  The current
    format gives about 30% shorter files and loads twice as fast.
  * Changed basic clause representation.  VM op-codes are now
    full machine words, avoiding the need for the `XR' table
    management and related indirections.  Simplifies the instruction set,
    speedup for compiler, decompiler (retract, clause) and execution
    (about 10%).  Enlarges program-size with about 10%.


Version 1.9.5:
==============

alpha-2

  * Fixed prolog_frame_attribute/3 for key=parent.
  * Added at_initialisation(+Goal) for initialisation hooks
  * Fixed tracer problems introduced in 1.9.5-alpla-1.


alpha-1

  * Moved sourcecode administration from predicate to individual
    clauses.  Purpose: better source-level debugger support, better
    handling of multifile predicates.

  * Recompiling files holding clauses for multifile predicates now
    works properly. The clauses of the latest loaded file will
    always be the last.

  * Removing a predicate from a file and recompiling the file
    now actually removes the definition from the Prolog database,
    even if you are not using modules.

  * Added prolog_frame_attribute(Frame, clause, ClauseRef) to get a
    reference to the currently running clause.

  * Added clause_property/2 to get the source information from a 
    specific clause.

  * Compiled state (-c compilation) has changed a little.  The system
    does not load old states.


Version 1.9.4.  Redefining system-predicates is no longer allowed.  This
may be overruled using  :-   redefine_system_predicate(+Head).   Fix  in
Makefile (from Kayvan Sylvan): fixes shell   syntax  error make install.
Give warning on user-files trying  to   load  module  `user' or `system'
(this is why library(system) could not   be loaded).  Fixed whereis/1 to
find locations of predicates.   Fixed   trace/[1,2]  to  avoid low-level
errors on bad specifications.  Specification now   also  accept the much
more natural ?- trace(append, fail).  as a shorthand for [+fail].  Added
autoloader handling to ed/1, listing/1, spy/1 and trace/2.  Manipulating
not-yet-loaded autoload predicates will trap the autoloader.  Added hook
for help-system, so we provide a   decent help-window when running under
the XPCE graphical environment.  The   hook  is called show_help_file/2.
Fixed  rename_file/2  (bug  introduced  in  pl-1.9.2).   Fixed  versions
Windows-specific problems.  Added  prolog_to_os_filename/2   to  convert
between internal and external names (DOS/Windows).  Integrated the 1.9.4
patches for the Windows  version.   Fixed   to  compile  on  AIX.  Fixed
compilation on some Solaris version.

Version  1.9.3.   Fix  index/1  problem    introduced   in  1.9.2.   Fix
stack-expansion problem in all versions that   lack hardware support for
stack-expansion.  Some cleanup in pl-gc.c to make clean compilation with
-Wall  and  -DO_DEBUG  possible.   Regenerated   common  prototype  file
pl-funcs.h using mkproto tool (and some editing).

Version 1.9.2.  Configuration is  now  based   on  GNU's  autoconf.  All
md-*.h files have been removed from  the distribution.  $arch/2, $home/1
and $version/1 have been replaced by feature/2.  A predicate read_link/3
has been added to read symbolic links.   Installation is tested on SunOs
4.1.3, Solaris 2.3 and Linux 1.0.9 with readline 2.0.3.

Version 1.9.1.  Added: Windows DDE   interface,  Added Unix/System-V (?)
interface to dlopen() and friends to access shared objects dynamically.

Version 1.9.0.  Incorporation of various  ports: md-netbsd.h, md-mswin.h
and  md-msdos.h.   There  is  a  binary   distribution  for  Windows  in
win-pl.tgz of the main ftp server (swi.psy.uva.nl).  The DOS and Windows
versions are created using the WATCOM-C/32 toolkit.


=======================================================================
Version 1.8.12.  Fixed tracer option `f' (fail) used on the exit port of
a goal.  Thanks to Thomas Hoppe.

Version 1.8.8.  Fix  in  the  parser   to  avoid  some  bad syntax-error
messages.  Also fixed spurious crashes   trying to read bad-syntax-terms
of the form ?- atom,.

New in the quintus.pl library:  initialization/1, random/3, numbervars/3
and absolute_file_name/3.

Version  1.8.7  includes   the    catch/throw-like   control  structures
block(+Label,  +Goal,  -Rval),  fail(+Label),  exit(+Label,  +Rval)  and
!(+Label).  Also new is explain(+Anything) which will  try to tell you a
lot of what the system knows about  the term you entered.  Additions and
suggesions are welcome.  Also new: library(bim): A partial Prolog-by-BIM
(tm) compatibility package by Henk Vandecasteele.  Thanks.

Further fixes:

	* Bug in detecting stack-overflow for the PC/linux version.
	* Handling of SWI_HOME_DIR (fixes installation problem for
 	  XPCE/SWI-Prolog).
	* atom_length/2: give warning (instead of crash) on invalid
	  data-type (e.g. unbound, term).
	* nth_clause/3: Removed errornous warning when cut-off and
	  fixed returning 0-reference for defined predicates without
	  clauses.

Version 1.8.6 defines phrase/[2,3] for accessing grammar rules and fixes
name/2 for numbers outside the  integer   range  (yielding  a float).  A
predicate nth_clause/3 is added to provide access to specific clauses of
predicates.  xmalloc(), xrealloc() are added to   fix some problems when
linking with gnu-libraries.

Version 1.8.5 contains a few fixes  for the SunOs-4/gcc-2.5 combination.
DONOT USE GCC-2.5.[123] as the optimiser   appears broken.  gcc-2.5.4 is
ok again.

Version 1.8.4 fixes =@=/2, contains a more  logical form of arg/3, fixes
passing empty-string arguments from the   Prolog  command-line and fixes
some things for old non-ansi compilers.    There  are some extensions to
the quintus.pl compatibility library.

Version 1.8.3 Fixes some  more  readline   problems  having  to  do with
running SWI-Prolog as an inferior process under EMACS.

Version 1.8.2 fixes some serious  problems   in  the tracer intoduced by
more global changes in 1.8.0.

Version 1.8.1 fixes load_foreign for  both   SunOs  4.1.3  and PC/Linux.
Extensive use of the stat(2) system call is reduced with some changes to
the file administration.  This speeds up loading  many small files by an
incredible amount, notably when reading over a (slow) network.

The manual is  regenerated.   There  are   not  many  changes,  but  the
PostScript files in these archives are  totally different as we upgrated
LaTeX and dvips.  Therefore  the   patch  file **diff-1.8.0-1.8.1** does
*not* include the patches to the PostScript manual.

Version 1.8.0 includes a stack  shifter,   enabling  dynamic  stacks for
machines that do not offer hardware support by providing suitable access
to  the  virtual  memory  management.    Fixed    a   bug  in  concat/3.
expand_file/2 is now sensitive to fileerrors/2   while expanding $var or
~user.   More  bugfixes  to  the    readline   interface.   Manual  page
contributed by Dave Sherrat.   RS6000  port   no  longer  uses -lbsd and
compiles on gcc.

================================================================
Version 1.7.2 should compile on Solaris 2.2   using gcc 2.4.5.  It fixes
the usual couple of portability problems,   the  terminal interface when
connected  to  the  XPCE  graphics  library.     It  ads  line_count  to
predicate_property to support a future graphical debugging tool.

Version 1.7.1 fixes a very serious   memory  allocation violation in the
connection to the readline library.  Make sure to update from 1.7.0!

Version 1.7.0 contains a version linked   with  the GNU readline library
for  bash/tcsh  compatible  line  editing.    The  library  readline  is
distributed separately and must be   installed before installing prolog.
The  file  readline-1.1.tar.gz  contains  the  unmodified  GNU  sources.
librl-1.1.tar.z contains the binaries for PC/Linux.

================================================================
Version 1.6.18 contains a fix to load_foreign/[2,5] for PC/Linux.

[Version 1.6.17 has been reinstalled at Jun  1 23:16 with two prototype
fixes and a fix to save_program/1 necessary for the RS6000.]

Version 1.6.17 fixes  some  minor   installation  problems  reported for
1.6.16.  The online manual has been   updated for trace/[1,2].  Callback
of undefined Prolog-predicates from C now correctly trap the autoloader.
Analysis of the PATH variable to  find   the  Prolog executable has been
fixed.  Nothing serious if you have a running system!

Version 1.6.16 integrates port to 386  System-V   Unix  made  by Eric S.
Raymond (esr@snark.thyrsus.com), who also ported   the  shell scripts to
use sh rather than csh.  The new   predicates  trace/1 and trace/2 allow
for tracing individual predicates non-interactively.

Version 1.6.15  eliminates  some  compiler  limits,   fixes  a  bug  in
trail-stacks management and provides a much   better  port for PC/Linux.
Requires Linux kernel 99pl7 or later.

Version 1.6.14 provides 8 bit character  support.  All characters in the
range 128 ...  255 are treated as   lowercase letters.  op/3 is fixed to
actually delete operators when priority 0 is specified.

Version 1.6.13 implements  standard  order   compatible  to  Quintus and
contains  a  fix  of  the  module  system  which  broke  the  Quintus.pl
replacement of retractall/1.

Version 1.6.12 is te result of  integrating   ports  to  LINUX, OS/2 and
HP/UX with the main-stream (SunOs).