NEWS

New in spot 2.7.5.dev (not yet released)

  Nothing yet.

New in spot 2.7.5 (2019-06-05)

  Build:

  - Although the Python bindings in this release are still done with
    Swig3.0, the code has been updated to be compatible with Swig4.0.

  Library:

  - print_dot will replace labels that have more 2048 characters by a
    "(label too long)" string.  This works around a limitation of
    GraphViz that aborts when some label exceeds 16k characters, and
    also helps making large automata more readable.

  Bugs fixed:

  - spot::translator was not applying Boolean sub-formula rewritting
    by default unless a spot::option_map was passed.  This caused some
    C++ code for translating certains formulas to be noticeably slower
    than the equivalent call to the ltl2tgba binary.

  - The remove_ap algorithm was preserving the "terminal property" of
    automata, but it is possible that a non-terminal input produces a
    terminal output after some propositions are removed.

New in spot 2.7.4 (2019-04-27)

  Bugs fixed:

  - separate_sets_here() (and therefore autfilt --separate-sets) could
    loop infinitely on some inputs.

  - In some situation, ltl2tgba -G could abort with
    "direct_simulation() requires separate Inf and Fin sets".  This
    was fixed by teaching simulation-based reductions how to deal
    with such cases.

  - The code for detecting syntactically stutter-invariant PSL
    formulas was incorrectly handling the ";" operator, causing some
    stutter-sensitive formulas to be flagged a stutter-invariant.

New in spot 2.7.3 (2019-04-19)

  Bugs fixed:

  - When processing CSV files with MSDOS-style \r\n line endings,
    --stats would output the \r as part of the %> sequence instead
    of ignoring it.

  - Fix serious typo in removel_alternation() causing incorrect
    output for some VWAA.  Bug introduced in Spot 2.6.

  Documentation:

  - Multiple typos and minor updates.

New in spot 2.7.2 (2019-03-17)

  Python:

  - Improved support for explicit Kripke structures.  It is now
    possible to iterate over a kripke_graph object in a way similar to
    twa_graph.

  Documentation:

  - A new page shows how to create explicit Kripke structures in C++
    and Python.  See https://spot.lrde.epita.fr/tut52.html
  - Another new page shows how to deal with LTLf formulas (i.e., LTL
    with finite semantics) and how to translate those.
    See https://spot.lrde.epita.fr/tut12.html

  Build:

  - Work around a spurious null dereference warning when compiling
    with --coverage and g++ 8.3.0-3 from Debian unstable.

New in spot 2.7.1 (2019-02-14)

  Build

  - Work around GCC bug #89303 that causes memory leaks and std::weak_bad_ptr
    exceptions when Spot is compiled with the version of g++ 8.2 currently
    distributed by Debian unstable (starting with g++ 8.2.0-15).

  Python:

  - The following methods of spot::bdd_dict are now usable in Python when
    fine control over the lifetime of associations between BDD variables
    and atomic propositions is needed.
    - register_proposition(formula, for_me)
    - register_anonymous_variables(count, for_me)
    - register_all_propositions_of(other, for_me)
    - unregister_all_my_variables(for_me)
    - unregister_variable(var, for_me)

  - Better support for explicit Kripke structures:
    - the kripke_graph type now has Python bindings
    - spot.automaton() and spot.automata() now support a want_kripke=True
      to return a kripke_graph
      See the bottom of https://spot.lrde.epita.fr/ipynb/ltsmin-dve.html
      for some examples.

  Library:

  - Printing Kripke structures via print_hoa() will save state names.

  - kripke_graph_ptr objects now honnor any "state-names" property
    when formating states.

  Bugs fixed:

  - The print_dot_psl() function would incorrectly number all but the
    first children of commutative n-ary operators: in this case no
    numbering was expected.

  - std::out_of_range C++ exceptions raised from Python code are now
    converted into IndexError Python exceptions (instead of aborting
    the program).

  - The LTL parser would choke on carriage returns when command-line
    tools such as ltlfilt, ltlcross, or ltl2tgba were run on files of
    formulas with MS-DOS line endings.

  - The core translation for unambiguous automata was incorrectly
    tagging some non-weak automata as weak.

  - The product_susp() function used to multiply an automaton with a
    suspendable automaton could incorrectly build transition-based
    automata when multipliying two state-based automata.  This caused
    ltl2tgba to emit error messages such as: "automaton has
    transition-based acceptance despite prop_state_acc()==true".

New in spot 2.7 (2018-12-11)

  Command-line tools:

  - ltlsynt now has three algorithms for synthesis:
    --algo=sd     is the historical one. The automaton of the formula
                  is split to separate inputs and outputs, then
                  determinized (with Safra construction).
    --algo=ds     the automaton of the formula is determinized (Safra),
                  then split to separate inputs and outputs.
    --algo=lar    translate the formula to a deterministic automaton
                  with an arbitrary acceptance condition, then turn it
                  into a parity automaton using LAR, and split it.
    In all three cases, the obtained parity game is solved using
    Zielonka algorithm. Calude's quasi-polynomial time algorithm has
    been dropped as it was not used.

  - ltlfilt learned --liveness to match formulas representing liveness
    properties.

  - the --stats= option of tools producing automata learned how to
    tell if an automaton uses universal branching (%u), or more
    precisely how many states (%[s]u) or edges (%[e]u) use universal
    branching.

  Python:

  - spot.translate() and spot.postprocess() now take an xargs=
    argument similar to the -x option of ltl2tgba and autfilt, making
    it easier to fine tune these operations.  For instance
        ltl2tgba 'GF(a <-> XXa)' --det -x gf-guarantee=0
    would be written in Python as
        spot.translate('GF(a <-> XXa)', 'det', xargs='gf-guarantee=0')
    (Note: those extra options are documented in the spot-x(7) man page.)

  - spot.is_generalized_rabin() and spot.is_generalized_streett() now return
    a tuple (b, v) where b is a Boolean, and v is the vector of the sizes
    of each generalized pair.  This is a backward incompatible change.

  Library:

  - The LTL parser learned syntactic sugar for nested ranges of X
    using the X[n], F[n:m], and G[n:m] syntax of TSLF.  (These
    correspond to the next!, next_e!, and next_a! operators of PSL,
    but we do not support those under these names currently.)

      X[6]a = XXXXXXa
      F[2:4]a = XX(a | X(a | Xa))
      G[2:4]a = XX(a & X(a & Xa))

    The corresponding constructors (for C++ and Python) are
      formula::X(unsigned, formula)
      formula::F(unsigned, unsigned, formula)
      formula::G(unsigned, unsigned, formula)

  - spot::unabbreviate(), used to rewrite away operators such as M or
    W, learned to use some shorter rewritings when an argument (e) is
    a pure eventuality or (u) is purely universal:

      Fe = e
      Gu = u
      f R u = u
      f M e = F(f & e)
      f W u = G(f | u)

  - The twa_graph class has a new dump_storage_as_dot() method
    to show its data structure.  This is more conveniently used
    as aut.show_storage() in a Jupyter notebook.  See
    https://spot.lrde.epita.fr/ipynb/twagraph-internals.html

  - spot::generic_emptiness_check() is a new function that performs
    emptiness checks of twa_graph_ptr (i.e., automata not built
    on-the-fly) with an *arbitrary* acceptance condition.  Its sister
    spot::generic_emptiness_check_scc() can be used to decide the
    emptiness of an SCC.  This is now used by
    twa_graph_ptr::is_empty(), twa_graph_ptr::intersects(), and
    scc_info::determine_unknown_acceptance().

  - The new function spot::to_parity() translates an automaton with
    arbitrary acceptance condition into a parity automaton, based on a
    last-appearance record (LAR) construction.  (It is used by ltlsynt
    but not yet by autfilt or ltl2tgba.)

  - The new function is_liveness() and is_liveness_automaton() can be
    used to check whether a formula or an automaton represents a
    liveness property.

  - Two new functions count_univbranch_states() and
    count_univbranch_edges() can help measuring the amount of
    universal branching in alternating automata.

  Bugs fixed:

  - translate() would incorrectly mark as stutter-invariant
    some automata produced from formulas of the form X(f...)
    where f... is syntactically stutter-invariant.

  - acc_cond::is_generalized_rabin() and
    acc_cond::is_generalized_streett() did not recognize the cases
    where a single generalized pair is used.

  - The pair of acc_cond::mark_t returned by
    acc_code::used_inf_fin_sets(), and the pair (bool,
    vector_rs_pairs) by acc_cond::is_rabin_like() and
    acc_cond::is_streett_like() were not usable in Python.

  - Many object types had __repr__() methods that would return the
    same string as __str__(), contrary to Python usage where repr(x)
    should try to show how to rebuild x.  The following types have
    been changed to follow this convention:
       spot.acc_code
       spot.acc_cond
       spot.atomic_prop_set
       spot.formula
       spot.mark_t
       spot.twa_run (__repr__ shows type and address)
       spot.twa_word (likewise, but _repr_latex_ used in notebooks)

    Note that this you were relying on the fact that Jupyter calls
    repr() to display returned values, you may want to call print()
    explicitely if you prefer the old representation.

  - Fix compilation under Cygwin and Alpine Linux, both choking
    on undefined secure_getenv().

New in spot 2.6.3 (2018-10-17)

  Bugs fixed:

  - Running "ltl2tgba -B" on formulas of the type FG(safety) would
    unexpectedly use a co-Büchi automaton as an intermediate step.
    This in turn caused "ltl2tgba -U -B" to not produce unambiguous
    automata.

  - ltl2tgba --low now disables the "gf-guarantee" feature, as
    documented.

  - ltlfilt's --accept-word and --reject-word options were ignored
    unless used together.

New in spot 2.6.2 (2018-09-28)

  Build:

  - We no longer distribute the Python-based CGI script + javascript
    code for the online translator.  Its replacement has its own
    repository: https://gitlab.lrde.epita.fr/spot/spot-web-app/

  Library:

  - When states are highlighted with more than 8 colors, print_dot()
    will add some extra markers to help distinguishing the colors.
    This helps with the fact that colors 8-15 are lighter versions of
    colors 0-7, and that higher color numbers cycle into this 16-color
    palette.

  Bugs fixed:

  - exclusive_ap::constrain() (called by autfilt --exclusive-ap=...)
    would incorrectly copy the "universal" property of the input
    automaton, causing print_hoa() to fail.

  - configure --disable-doxygen would actually enable it.

  - Fix several warnings emited by the development version of GCC.

New in spot 2.6.1  (2018-08-04)

  Command-line tools:

  - "ltlfilt --suspendable" is now a synonym for
    "ltlfilt --universal --eventual".

  Bugs fixed:

  - scc_info::split_on_sets() did not correctly register the
    atomic propositions of the returned automata.

  - The spot::tl_simplifier class could raise an exception while
    attempting to reduce formulas containing unsimplified <->, -> or
    xor, if options nenoform_stop_on_boolean and synt_impl are both
    set.  (This combination of options is not available from
    command-line tools.)

  - The spot::contains(a, b) function introduced in 2.6 was testing
    a⊆b instead of a⊇b as one would expect.  Infortunately the
    documentation was also matching the code, so this is a backward
    incompatible change, but a short-lived one.

  - The Python binding of the getter of spot::parsed_formula::f was
    returning a reference instead of a copy, causing issues if the
    reference outlasted the parsed_formula struct.


New in spot 2.6  (2018-07-04)

  Command-line tools:

  - autfilt learned --is-colored to filter automata that use
    exactly one acceptance set per mark or transition.

  - autfilt learned --has-univ-branching and --has-exist-branching
    to keep automata that have universal branching, or that make
    non-deterministic choices.

  - autcross' tool specifications now have %M replaced by the name of
    the input automaton.

  - autcross now aborts if there is any parser diagnostic for the
    input automata (previous versions would use the input automaton
    whenever the parser would manage to read something).

  - ltlcross, ltldo, and autcross learned shorthands to call
    delag, ltl2dra, ltl2dgra, and nba2dpa.

  - When autfilt is asked to build a Büchi automaton from
    of a chain of many products, as in
    "autfilt -B --product 1.hoa ... --product n.hoa in.hoa"
    then it will automatically degeneralize the intermediate
    products to avoid exceeding the number of supported
    acceptance sets.

  - genltl learned to generate six new families of LTL formulas:
      --gf-equiv-xn=RANGE    GF(a <-> X^n(a))
      --gf-implies-xn=RANGE  GF(a -> X^n(a))
      --sejk-f=RANGE[,RANGE] f(0,j)=(GFa0 U X^j(b)), f(i,j)=(GFai U
                             G(f(i-1,j)))
      --sejk-j=RANGE         (GFa1&...&GFan) -> (GFb1&...&GFbn)
      --sejk-k=RANGE         (GFa1|FGb1)&...&(GFan|FGbn)
      --sejk-patterns[=RANGE]   φ₁,φ₂,φ₃ from Sikert et al's [CAV'16]
                             paper (range should be included in 1..3)

  - genltl --ms-example can now take a two-range argument,
    (as --sejk-f above).

  Build:

  - ./configure --enable-max-accsets=N let you specify a maximum
    number of acceptance sets that Spot should support.  The default
    is still 32, but this limit is no longer hardcoded.  Larger values
    will cost additional memory and time.

  - We know distribute RPM packages for Fedora 28.  See
    file:///home/adl/git/spot/doc/userdoc/install.html#Fedora

  Library:

  - The PSL/LTL simplification routine learned the following:

      q R Xf = X(q R f)  if q is suspendable
      q U Xf = X(q U f)  if q is suspendable
      {SERE;1} = {1}     if {SERE} accepts [*0]
      {SERE;1} = {SERE}  if {SERE} does not accept [*0]

  - gf_guarantee_to_ba() is a specialized construction for translating
    formulas of the form GF(guarantee) to BA or DBA, and
    fg_safety_to_dca() is a specialized construction for translating
    formulas of the form FG(safety) to DCA.  These are generalizations
    of some constructions proposed by J. Esparza, J. Křentínský, and
    S. Sickert (LICS'18).

    These are now used by the main translation routine, and can be
    disabled by passing -x '!gf-guarantee' to ltl2tgba.  For example,
    here are the size of deterministic transition-based generalized
    Büchi automata constructed from four GF(guarantee) formulas with
    two versions of Spot, and converted to other types of
    deterministic automata by other tools distributed with Owl 18.06.
    "x(y)" means x states and y acceptance sets.

                               ltl2tgba -D  delag ltl2dra
                                2.5   2.6   18.06  18.06
    -------------------------  -----------  -------------
    GF(a <-> XXa)               9(1)  4(1)   4(2)   9(4)
    GF(a <-> XXXa)             27(1)  8(1)   8(2)  25(4)
    GF(((a & Xb) | XXc) & Xd)   6(1)  4(1)  16(1)   5(2)
    GF((b | Fa) & (b R Xb))     6(2)  2(1)   3(4)   3(4)

    Note that in the above the automata produced by 'ltl2tgba -D' in
    version 2.5 were not deterministic (because -D is only a
    preference).  They are deterministic in 2.6 and other tools.

  - spot::product() and spot::product_or() learned to produce an
    automaton with a simpler acceptance condition if one of the
    argument is a weak automaton.  In this case the resulting
    acceptance condition is (usually) that of the other argument.

  - spot::product_susp() and spot::product_or_susp() are new
    functions for building products between an automaton A and
    a "suspendable" automaton B.  They are also optimized for
    the case that A is weak.

  - When 'generic' acceptance is enabled, the translation routine will
    split the input formula on Boolean operators into components that
    are syntactically 'obligation', 'suspendable', or 'something
    else'.  Those will be translated separately and combined with
    product()/product_susp().  This is inspired by the ways things are
    done in ltl2dstar or delag, and can be disabled by passing option
    -xltl-split=0, as in ltl2tgba -G -D -xltl-split=0.  Here are the
    sizes of deterministic automata (except for ltl3tela which produces
    non-deterministic automata) produced with generic acceptance
    using two versions of ltl2tgba and other tools for reference.

                                             ltl2tgba -DG  delag  ltl3tela
                                              2.5    2.6   18.06    1.1.2
                                             ------------ ------- --------
    FGa0&GFb0                                 2(2)   1(2)   1(2)    1(2)
    (FGa1&GFb1)|FGa0|GFb0                    16(6)   1(4)   1(4)    1(9)
    (FGa2&GFb2)|((FGa1|GFb1)&FGa0&GFb0)      29(8)   1(6)   1(6)    3(11)
    FGa0|GFb0                                 5(4)   1(2)   1(2)    1(5)
    (FGa1|GFb1)&FGa0&GFb0                     8(4)   1(4)   1(4)    1(7)
    (FGa2|GFb2)&((FGa1&GFb1)|FGa0|GFb0)     497(14)  1(6)   1(6)    1(14)
    GFa1 <-> GFz                              4(6)   1(3)   1(4)    1(7)
    (GFa1 & GFa2) <-> GFz                     8(4)   1(3)   1(6)    3(10)
    (GFa1 & GFa2 & GFa3) <-> GFz             21(4)   1(4)   1(8)    3(13)
    GFa1 -> GFz                               5(4)   1(2)   1(2)    1(5)
    (GFa1 & GFa2) -> GFz                     12(4)   1(3)   1(3)    1(6)
    (GFa1 & GFa2 & GFa3) -> GFz              41(4)   1(4)   1(4)    1(7)
    FG(a|b)|FG(!a|Xb)                         4(2)   2(2)   2(2)    2(3)
    FG(a|b)|FG(!a|Xb)|FG(a|XXb)              21(2)   4(3)   4(3)    4(4)
    FG(a|b)|FG(!a|Xb)|FG(a|XXb)|FG(!a|XXXb) 170(2)   8(4)   8(4)    8(5)

  - For 'parity' output, the 'ltl-split' optimization just separates
    obligation subformulas from the rest, where a determinization is
    still performed.
                                 ltl2tgba -DP  ltl3dra  ltl2dpa
                                   2.5   2.6    0.2.3    18.06
                                -------------- -------  -------
    FGp0 & (Gp1 | XFp2)           6(2)  4(1)     4(1)     4(2)
    G!p0 | F(p0 & (!p1 W p2))     5(2)  4(2)     n/a      5(2)
    (p0 W XXGp0) & GFp1 & FGp2    6(2)  5(2)     n/a      6(3)

    (The above just show a few cases that were improved.  There are
    many cases where ltl2dpa still produces smaller automata.)

  - The automaton postprocessor will now simplify acceptance
    conditions more aggressively, calling spot::simplify_acceptance()
    or spot::cleanup_acceptance() depending on the optimization level.

  - print_dot(), used to print automata in GraphViz's format,
    underwent several changes:

    * option "a", for printing the acceptance condition, is now
      enabled by default.  Option "A", introduced in Spot 2.4, can be
      used to hide the acceptance condition in case you do not want
      it.  This change of course affects the --dot option of all the
      command-line tools, as well as the various way to display
      automata using the Python bindings.

    * when option "1" is used to hide state names and force the
      display of state numbers, the actual state names is now moved to
      the "tooltip" field of the state.  The SVG files produced by
      "dot -Tsvg" will show those as popups.  This is also done for
      state labels of Kripke structures.

    * the output digraph is now named using the name of the automaton
      if available, or the empty string otherwise.  (Previous versions
      used to call all digraphs "G".)  This name appears as a tooltip
      in SVG figures when the mouse is over the acceptance condition.

    * a new option "u" hides "true states" behind "exiting
      transitions".  This can be used to display alternating automata
      in a way many people expect.

    * a new option "K" cancels the effect of "k" (which uses state
      labels whenever possible).  This is most useful when one want to
      force transition-labeling of a Kripke structure, where "k" is
      usually the default.

  - spot::twa_graph::merge_states() is a new method that merges states
    with the exact same outgoing edges. As it performs no reordering
    of the edges, it is better to call it when you know that the edges
    in the twa_graph are sorted (e.g. after a call to merge_edges()).

  - spot::twa_graph::purge_unreachable_states() now takes a function
    which is called with the new numbering of states. This is useful
    to update an external structure that references states of the twa
    that we want to purge.

  - spot::scc_filter() now automatically turns automata marked as
    inherently-weak into weak automata with state-based acceptance.
    The acceptance condition is set to Büchi unless the input had
    co-Büchi or t acceptance.  spot::scc_filter_states() will pass
    inherently-weak automata to spot::scc_filter().

  - spot::cleanup_parity() and spot::cleanup_parity_here() are smarter
    and now remove from the acceptance condition the parity colors
    that are not used in the automaton.

  - spot::contains() and spot::are_equivalent() can be used to
    check language containement between two automata or formulas.
    They are most welcome in Python, since we used to redefine
    them every now and them.  Some examples are shown in
    https://spot.lrde.epita.fr/ipynb/contains.html

  - aut1->exclusive_word(aut2) is a new method that returns a word
    accepted by aut1 or aut2 but not both.  The exclusive_run()
    variant will return.  This is useful when comparing automata and
    looking for differences.  See also
    https://spot.lrde.epita.fr/ipynb/contains.html

  - spot::complement_semidet(aut) is a new function that returns the
    complement of aut, where aut is a semideterministic automaton. The
    function uses the NCSB complementation algorithm proposed by
    F. Blahoudek, M. Heizmann, S. Schewe, J. Strejček, and MH. Tsai
    (TACAS'16).

  - spot::remove_alternation() was slightly improved on very-weak
    alternating automata: the labeling of the outgoing transitions in
    the resulting TGBA makes it more likely that simulation-based
    reductions will reduce it.

  - When applied to automata that are not WDBA-realizable,
    spot::minimize_wdba() was changed to produce an automaton
    recognizing a language that includes the original one.  As a
    consequence spot::minimize_obligation() and
    spot::is_wdba_realizable() now only need one containement check
    instead of two.

  - Slightly improved log output for the SAT-based minimization
    functions.  The CSV log files now include an additional column
    with the size of the reference automaton, and they now have a
    header line.  These log files give more details and are more
    accurate in the case of incremental SAT-solving.

  Python:

  - New spot.jupyter package.  This currently contains a function for
    displaying several arguments side by side in a Jupyter notebook.
    See https://spot.lrde.epita.fr/ipynb/alternation.html for some
    examples.

  - Strings are now implicitely converted into formulas when passed
    as arguments to functions that expect formulas.  Previously this
    was done only for a few functions.

  - The Python bindings for sat_minimize() now have display_log and
    return_log options; these are demonstrated on the new
    https://spot.lrde.epita.fr/ipynb/satmin.html page.

  Bugs fixed:

  - Python *.py and *.so files are now always installed into the same
    directory.  This was an issue on systems like Fedora that separate
    plateform-specific packages from non-plateform-specific ones.

  - print_dot() will correctly escape strings containing \n in HTML
    mode.

  - The HOA parser will now accept Alias: declarations that occur
    before AP:.

  - The option --allow-dups of randltl now works properly.

  - Converting generalized-co-Büchi to Streett using dnf_to_nca()
    could produce bogus automata if the input had rejecting SCCs.

  Deprecation notices:

  - The type spot::acc_cond::mark_t has been overhauled and uses
    a custom bit-vector to represent acceptance sets instead of
    storing everything in a "unsigned int".  This change is
    to accomodate configure's --enable-max-accsets=N option and
    has several effect:

    * The following shortcuts are deprecated:
        acc_cond::mark_t m1 = 0U;
        acc_cond::mark_t m2 = -1U;
      instead, use:
        acc_cond::mark_t m1 = {};
        acc_cond::mark_t m2 = acc_cond::mark_t::all();

    * acc_cond::mark_t::value_t is deprecated.  It is now only
      defined when --enable-max-accsets=32 (the default) and
      equal to "unsigned" for backward compatibility reasons.

  Backward incompatibilities:

  - Functions spot::parity_product() and spot::parity_product_or()
    were removed.  The code was unused, hard to maintain, and bogus.

  - The output of print_dot() now include the acceptance condition.
    Add option "A" (supported since version 2.4) to cancel that.

  - Because genltl now supports LTL pattern with two argumens, using
    --format=%L may output two comma-separated integer.  This is an
    issue if you used to produce CSV files using for instance:
      genltl --format='%F,%L,%f' ...
    Make sure to quote %L to protect the potential commas:
      genltl --format='%F,"%L",%f' ...

  - In Spot 2.5 and prior running "ltl2tgba --generic --det" on some
    formula would attempt to translate it as deterministic TGBA or
    determinize it into an automaton with parity acceptance.  Version
    2.5 introduced --parity to force parity acceptance on the output.
    This version finally gives --generic some more natural semantics:
    any acceptance condition can be used.


New in spot 2.5.3 (2018-04-20)

  Bugs fixed:

  - "autfilt --cobuchi --small/--det" would turn a transition-based
    co-Büchi automaton into a state-based co-Büchi.

  - Fix cryptic error message from Python's spot.translate() and
    spot.postprocess() when supplying conflicting arguments.

  - "autfilt -B --sat-minimize" was incorrectly producing
    transition-based automata.

  - Using spot.automata("cmd...|") to read just a few automata out of
    an infinite stream would not properly terminate the command.

  - The is_unambiguous() check (rewritten in Spot 2.2) could mark some
    unambiguous automata as ambiguous.

New in spot 2.5.2 (2018-03-25)

  Bugs fixed:

  - acc_cond::is_generalized_rabin() and
    acc_cond::is_generalized_streett() would segfault on weird
    acceptance conditions such as "3 t" or "3 f".

  - remove_fin() and streett_to_generalized_buchi() should never
    return automata with "f" acceptance.

  - "autfilt --acceptance-is=Fin-less" no longer accept automata
    with "f" acceptance.

  - twa_run methods will now diagnose cases where the cycle is
    unexpectedly empty instead of segfaulting.

  - spot::closure(), used by default for testing stutter-invariance,
    was using an optimization incorrect if the acceptance condition
    had some Fin(x).  Consequently stutter-invariance tests for
    automata, for instance with "autfilt --is-stutter-invariant",
    could be to be wrong (even if the input does not use Fin(x), its
    complement, used in the stutter-invariance test likely will).
    Stutter-invariance checks of LTL formulas are not affected.

New in spot 2.5.1 (2018-02-20)

  Library:

  - iar() and iar_maybe() now also handle Streett-like conditions.

  Bugs fixed:

  - iar() and iar_maybe() properly handle Rabin-like conditions.

  - streett_to_generalized_buchi() could produce incorrect result on
    Streett-like input with acceptance like (Inf(0)|Fin(1))&Fin(1)
    where some Fin(x) is used both with and without a paired Fin(y).

  - is_generalized_rabin() had a typo that caused some non-simplified
    acceptance conditions like Fin(0)|(Fin(0)&Inf(1)) to be
    incorrectly detecteded as generalized-Rabin 2 0 1 and then output
    as Fin(0)|(Fin(1)&Inf(2)) instead.  Likewise for
    is_generalized_streett

  - the conversion from Rabin to Büchi was broken on Rabin-like
    acceptance condition where one pair used Fin(x) and another pair
    used Inf(x) with the same x.  Unfortunately, this situation could
    also occur as a side effect of simplifying the acceptance
    condition (by merging identical set) of some automaton prior to
    converting it to Büchi.

  - dnf_to_dca() was mishandling some Rabin-like input.

New in spot 2.5 (2018-01-20)

  Build:

  - We no longer distribute the doxygen-generated documentation in
    the tarball of Spot to save space.  This documentation is still
    available online at https://spot.lrde.epita.fr/doxygen/.  If you
    want to build a local copy you can configure Spot with
    --enable-doxygen, or simply run "cd doc && make doc".

  - All the images that illustrate the documentation have been
    converted to SVG, to save space and improve quality.

  Tools:

  - ltlsynt is a new tool for synthesizing a controller from LTL/PSL
    specifications.

  - ltlcross learned --reference=COMMANDFMT to specify a translator
    that should be trusted.  Doing so makes it possible to reduce the
    number of tests to be performed, as all other translators will be
    compared to the reference's output when available.  Multiple
    reference can be given; in that case other tools are compared
    against the smallest reference automaton.

  - autcross, ltlcross, and ltldo learned --fail-on-timeout.

  - ltl2tgba, autfilt, and dstar2tgba have some new '--parity' and
    '--colored-parity' options to force parity acceptance on the
    output.  Different styles can be requested using for instance
    --parity='min odd' or --parity='max even'.

  - ltl2tgba, autfilt, and dstar2tgba have some new '--cobuchi' option
    to force co-Büchi acceptance on the output.  Beware: if the input
    language is not co-Büchi realizable the output automaton will
    recognize a superset of the input.  Currently, the output is
    always state-based.

  - genltl learned to generate six new families of formulas, taken from
    the SYNTCOMP competition on reactive synthesis, and from from
    Müller & Sickert's GandALF'17 paper:
    --gf-equiv=RANGE       (GFa1 & GFa2 & ... & GFan) <-> GFz
    --gf-implies=RANGE     (GFa1 & GFa2 & ... & GFan) -> GFz
    --ms-example=RANGE     GF(a1&X(a2&X(a3&...)))&F(b1&F(b2&F(b3&...)))
    --ms-phi-h=RANGE       FG(a|b)|FG(!a|Xb)|FG(a|XXb)|FG(!a|XXXb)|...
    --ms-phi-r=RANGE       (FGa{n}&GFb{n})|((FGa{n-1}|GFb{n-1})&(...))
    --ms-phi-s=RANGE       (FGa{n}|GFb{n})&((FGa{n-1}&GFb{n-1})|(...))

  - autfilt learned --streett-like to convert automata with DNF
    acceptance into automata with Streett-like acceptance.

  - autfilt learned --acceptance-is=ACC to filter automata by
    acceptance condition.  ACC can be the name of some acceptance
    class (e.g. Büchi, Fin-less, Streett-like) or a precise acceptance
    formula in the HOA syntax.

  - ltldo learned to limit the number of automata it outputs using -n.

  - ltlfilt learned to measure wall-time using --format=%r, and
    cpu-time with --format=%R.

  - The --format=%g option of tools that output automata used to
    print the acceptance condition as a *formula* in the HOA format.
    This %g may now take optional arguments to print the acceptance
    *name* in different formats.  For instance

       ... | autfilt -o '%[s]g.hoa'

    will separate a stream of automata into different files named
    by their acceptance name (Buchi, co-Buchi, Streett, etc.) or
    "other" if no name is known for the acceptance condition.

  - Tools that produce formulas now support --format=%[OP]n to
    display the nesting depth of operator OP.

  - The new -x tls-impl=N option allows to fine-tune the
    implication-based simplification rules of ltl2tgba.  See the
    spot-x(7) man page for details.

  - All tools learned to check the SPOT_OOM_ABORT environment
    variable.  This is only useful for debuging out-of-memory
    conditions. See the spot-x(7) man page for details.

  New functions in the library:

  - spot::iar() and spot::iar_maybe() use index appearance records (IAR)
    to translate Rabin-like automata into equivalent parity automata.
    This translation preserves determinism and is especially useful when
    the input automaton is deterministic.

  - spot::print_aiger() encodes an automaton as an AIGER circuit, as
    required by the SYNTCOMP competition.  It relies on a new named
    property "synthesis outputs" that describes which atomic
    propositions are to be encoded as outputs of the circuits.

  - spot::dnf_to_streett() converts any automaton with a DNF
    acceptance condition into a Streett-like automaton.

  - spot::nsa_to_nca(), spot::dfn_to_nca(), spot::dfn_to_dca(), and
    spot::nsa_to_dca(), convert automata with DNF or Streett-like
    acceptance into deterministic or non-deterministic co-Büchi
    automata.  spot::to_dca() and spot::to_nca() dispatch between
    these four functions.  The language of produced automaton includes
    the original language, but may be larger if the original automaton
    is not co-Büchi realizable.  Based on Boker & Kupferman FOSSACS'11
    paper.  Currently only supports state-based output.

  - spot::scc_info::states_on_acc_cycle_of() returns all states
    visited by any accepting cycle of the specified SCC.  It only
    works on automata with Streett-like acceptance.

  - spot::is_recurrence(), spot::is_persistence(), and
    spot::is_obligation() test if a formula is a recurrence,
    persistance or obligation.  The SPOT_PR_CHECK and SPOT_O_CHECK
    environment variables can be used to select between multiple
    implementations of these functions (see the spot-x(7) man page).

  - spot::is_colored() checks if an automaton is colored
    (i.e., every transition belongs to exactly one acceptance set).

  - spot::change_parity() converts between different parity acceptance
    conditions.

  - spot::colorize_parity() transforms an automaton with parity
    acceptance into a colored automaton (which is often what people
    working with parity automata expect).

  - spot::cleanup_parity_acceptance() simplifies a parity acceptance
    condition.

  - spot::parity_product() and spot::parity_product_or() are
    specialized (but expensive) products that preserve parity
    acceptance.

  - spot::remove_univ_otf() removes universal transitions on the fly
    from an alternating Büchi automaton using Miyano and Hayashi's
    breakpoint algorithm.

  - spot::stutter_invariant_states(),
    spot::stutter_invariant_letters(),
    spot::highlight_stutter_invariant_states(), ...  These functions
    help study a stutter-sensitive automaton and detect the subset of
    states that are stutter-invariant.  See
    https://spot.lrde.epita.fr/ipynb/stutter-inv.html for examples.

  - spot::acc_cond::name(fmt) is a new method that names well-known
    acceptance conditions.  The fmt parameter specifies the format to
    use for that name (e.g. to the style used in HOA, or that used by
    print_dot()).

  - spot::formula::is_leaf() method can be used to detect formulas
    without children (atomic propositions, or constants).

  - spot::nesting_depth() computes the nesting depth of any LTL
    operator.

  - spot::check_determinism() sets both prop_semi_deterministic()
    and prop_universal() appropriately.

  Improvements to existing functions in the library:

  - spot::tgba_determinize() has been heavily rewritten and
    optimized. The algorithm has (almost) not changed, but it is
    much faster now. It also features an optimization for
    stutter-invariant automata that may produce slightly smaller
    automata.

  - spot::scc_info now takes an optional argument to disable some
    features that are expensive and not always necessary.  By
    default scc_info tracks the list of all states that belong to an
    SCC (you may now ask it not to), tracks the successor SCCs of
    each SCC (that can but turned off), and explores all SCCs of the
    automaton (you may request to stop on the first SCC that is
    found accepting).

  - In some cases, spot::degeneralize() would output Büchi automata
    with more SCCs than its input.  This was hard to notice, because
    very often simulation-based simplifications remove those extra
    SCCs.  This situation is now detected by spot::degeneralized()
    and fixed before returning the automaton.  A new optional
    argument can be passed to disable this behavior (or use -x
    degen-remscc=0 from the command-line).

  - The functions for detecting stutter-invariant formulas or
    automata have been overhauled.  Their interface changed
    slightly.  They are now fully documented.

  - spot::postprocessor::set_type() can now request different forms
    of parity acceptance as output.  However currently the
    conversions are not very smart: if the input does not already
    have parity acceptance, it will simply be degeneralized or
    determinized.

  - spot::postprocessor::set_type() can now request co-Büchi
    acceptance as output.  This calls the aforementioned to_nca() or
    to_dca() functions.

  - spot::remove_fin() will now call simplify_acceptance(),
    introduced in 2.4, before attempting its different Fin-removal
    strategies.

  - spot::simplify_acceptance() was already merging identical
    acceptance sets, and detecting complementary sets i and j to
    perform the following simplifications
      Fin(i) & Inf(j) = Fin(i)
      Fin(i) | Inf(j) = Inf(i)
    It now additionally applies the following rules (again assuming i
    and j are complementary):
      Fin(i) & Fin(j) = f          Inf(i) | Inf(j) = t
      Fin(i) & Inf(i) = f          Fin(i) | Inf(i) = t

  - spot::formula::map(fun) and spot::formula::traverse(fun) will
    accept additionnal arguments and pass them to fun().  See
    https://spot.lrde.epita.fr/tut03.html for some examples.

  Python-specific changes:

  - The "product-states" property of automata is now accessible via
    spot.twa.get_product_states() and spot.twa.set_product_states().

  - twa_word instances can be displayed as SVG pictures, with one
    signal per atomic proposition.  For some examples, see the use of
    the show() method in https://spot.lrde.epita.fr/ipynb/word.html

  - The test suite is now using v4 of the Jupyter Notebook format.

  - The function rabin_is_buchi_realizable() as its name suggests checks
    if a rabin aut. is Büchi realizable. It is heavily based on
    tra_to_tba() algorithm.

  Deprecation notices:

  (These functions still work but compilers emit warnings.)

  - spot::scc_info::used_acc(), spot::scc_info::used_acc_of() and
    spot::scc_info::acc() are deprecated.  They have been renamed
    spot::scc_info::marks(), spot::scc_info::marks_of() and
    spot::scc_info::acc_sets_of() respectively for clarity.

  Backward incompatible changes:

  - The spot::closure(), spot::sl2(), spot::is_stutter_invariant()
    functions no longer take && arguments.  The former two have
    spot::closure_inplace() and spot::sl2_inplace() variants.  These
    functions also do not take a list of atomic propositions as an
    argument anymore.

  - The spot::bmrand() and spot::prand() functions have been removed.
    They were not used at all in Spot, and it is not Spot's objective
    to provide such random functions.

  - The spot::bdd_dict::register_all_propositions_of() function has
    been removed.  This low-level function was not used anywhere in
    Spot anymore, since it's better to use spot::twa::copy_ap_of().

  Bugs fixed:

  - spot::simplify_acceptance() could produce incorrect output if the
    first edge of the automaton was the only one with no acceptance
    set.  In spot 2.4.x this function was only used by autfilt
    --simplify-acceptance; in 2.5 it is now used in remove_fin().

  - spot::streett_to_generalized_buchi() could generate incorrect
    automata with empty language if some Fin set did not intersect all
    accepting SCCs (in other words, the fix from 2.4.1 was incorrect).

  - ltlcross could crash when calling remove_fin() on an automaton
    with 32 acceptance sets that would need an additional set.

  - the down_cast() helper function used in severaly headers of Spot
    was not in the spot namespace, and caused issues with some
    configurations of GCC.

New in spot 2.4.4 (2017-12-25)

  Bugs fixed:

  - The generic to_generalized_buchi() function would fail if the
    Fin-less & CNF version of the acceptance condition had several
    unit clauses.

  - If the automaton passed to sbacc() was incomplete or
    non-deterministic because of some unreachable states, then it was
    possible that the output would marked similarly while it was in
    fact complete or deterministic.

New in spot 2.4.3 (2017-12-19)

  Bugs fixed:

  - couvreur99_new() leaked memory when processing TωA that allocate
    states.