See the following valgrind output excerpts (for a run over input & | F p F q F r):

==7006== Use of uninitialised value of size 4
==7006== at 0x485BB58: ??? (in /usr/lib/arm-linux-gnueabihf/libarmmem-v7l.so)
==7006== by 0x20377: std::char_traits::copy(char*, char const*, unsigned int) (char_traits.h:409)
==7006== by 0x2107F: std::__cxx11::basic_string<char, std::char_traits, std::allocator >::_S_copy(char*, char const*, unsigned int) (basic_string.h:351)
==7006== by 0x209EF: std::__cxx11::basic_string<char, std::char_traits, std::allocator >::operator=(std::__cxx11::basic_string<char, std::char_traits, std::allocator >&&) (basic_string.h:722)
==7006== by 0x1FF63: operator<<(std::ostream&, Formula const*) (formula.cpp:63)
==7006== by 0x20013: std::less<Formula*>::operator()(Formula* const&, Formula* const&) const (formula.cpp:73)
==7006== by 0x29EA3: std::_Rb_tree<Formula*, Formula*, std::_Identity<Formula*>, std::less<Formula*>, std::allocator<Formula*> >::_M_lower_bound(std::_Rb_tree_node<Formula*>, std::_Rb_tree_node_base, Formula* const&) (stl_tree.h:1935)
==7006== by 0x29B6B: std::_Rb_tree<Formula*, Formula*, std::_Identity<Formula*>, std::less<Formula*>, std::allocator<Formula*> >::find(Formula* const&) (stl_tree.h:2553)
==7006== by 0x2993B: std::set<Formula*, std::less<Formula*>, std::allocator<Formula*> >::find(Formula* const&) (stl_set.h:795)
==7006== by 0x2955B: CommutativeFormula::read(std::istream&) (commutativeformula.cpp:34)
==7006== by 0x1FB7B: Formula::parse(std::istream&) (formula.cpp:34)
==7006== by 0x29513: CommutativeFormula::read(std::istream&) (commutativeformula.cpp:31)

Currently the Makefile recompiles all source from scratch upon reach run. On my current development machine (Raspberry Pi 3 Model B), this is prohibitively slow.

This'll make things significantly more readable while also serving as a refresher after an ~8 year absence.

Include a command-line option to control whether a dead state (the state corresponding to the formula false which loops on all worlds) is included in the automaton.

Ideally there should be no need for any explicit calls to new or delete. Try moving to unique_ptr and/or value-based semantics wherever possible.

One such input: U F p F q

(representing the LTL formula (F p) U (F q))

The function std::less<Formula*>::operator(Formula* const&, Formula* const&) orders Formula pointer values according to the ordering of their string representations.

Two commutative binary formulas will not be equal according to this ordering, if their subformulas are swapped. For example, The disjunction p | q will be considered less than q | p, when it should be equal.

One solution is to make BinaryFormula::write(std::ostream&) print the operands in alphabetical order for commutative binary formulas. Consider a subclass for commutative formulas to prevent duplicate code.

Subject line says it -- project currently has zero testing!