We are happy to announce the release of Spot 2.7 Someone recently reported some release-worthy bug, and unfortunately we do not have time to prepare a 2.6.4 release by cherry-picking the bug fixes from the development branch. So here is Spot 2.7 instead, with some minor new features and backward-incompatible changes done over the last 5 months. See the list below for details. This release contains contributions by Maximilien Colange, Etienne Renault, and myself. You can find the new release here: http://www.lrde.epita.fr/dload/spot/spot-2.7.tar.gz See https://spot.lrde.epita.fr/ for documentation and installation instructions. As always, please direct any feedback to &lt;spot(a)lrde.epita.fr&gt;fr>. 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 were 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().