Stephen¶

class Stephen : public libsemigroups::Runner ¶

Defined in stephen.hpp.

On this page we describe the functionality in libsemigroups relating to Stephen’s procedure for finitely presented semigroups. This class implements Stephen’s procedure for (possibly) constructing the word graph (ActionDigraph) corresponding to the left factors of a word in a finitely presented semigroup. The algorithm implemented in this class is closely related to the Todd-Coxeter algorithm (as implemented in congruence::ToddCoxeter) and originates in Applications of automata theory to presentations of monoids and inverse monoids by J. B. Stephen.

Member types¶

`digraph_type`	The return type of the function `word_graph` .
`node_type`	The type of the nodes of a `digraph_type` .

Constructor¶

`Stephen()`	Default constructor.
`Stephen(P &&)`	Construct from a presentation.
`Stephen(Stephen &&) = default`	Default move constructor.
`Stephen(Stephen const &) = default`	Default copy constructor.
`operator=(Stephen &&) = default`	Default move assignment operator.
`operator=(Stephen const &) = default`	Default copy assignment operator.

Initialization¶

`init(P &&)`	Initialize from a presentation.
`set_word(word_type &&)`	Set the word.
`set_word(word_type const &)`	Set the word.

Defining data¶

`presentation() const noexcept`	The input presentation.
`word() const noexcept`	The word.

Results of the algorithm¶

`accept_state()`	The accept state of the word graph.
`word_graph() const noexcept`	The word graph.

Member functions inherited from Runner¶

`dead() const noexcept`	Check if the runner is dead.
`finished() const`	Check if `run` has been run to completion or not.
`kill() noexcept`	Stop `run` from running (thread-safe).
`report() const`	Check if it is time to report.
`report_every() const noexcept`	Get the minimum elapsed time between reports.
`report_every(TIntType)`	Set the minimum elapsed time between reports.
`report_every(std::chrono::nanoseconds)`	Set the minimum elapsed time between reports.
`report_why_we_stopped() const`	Report why `run` stopped.
`run()`	Run until `finished` .
`run_for(TIntType)`	Run for a specified amount of time.
`run_for(std::chrono::nanoseconds)`	Run for a specified amount of time.
`run_until(T&&)`	Run until a nullary predicate returns `true` or `finished` .
`run_until(bool(*)())`	Run until a nullary predicate returns `true` or `finished` .
`running() const noexcept`	Check if currently running.
`running_for() const noexcept`	Check if the runner is currently running for a particular length of time.
`running_until() const noexcept`	Check if the runner is currently running until a nullary predicate returns `true`.
`started() const`	Check if `run` has been called at least once before.
`stopped() const`	Check if the runner is stopped.
`stopped_by_predicate() const`	Check if the runner was, or should, stop because of the argument for `run_until` .
`timed_out() const`	Check if the amount of time passed to `run_for` has elapsed.