Creating an automaton in C++
This example demonstrates how to create an automaton in C++, and then print it. The interface
#include <iostream> #include "twaalgos/hoa.hh" #include "twa/twagraph.hh" int main(void) { // The dict is used to maintain the correspondence between the // atomic propositions and the BDD variables to label the edges of // the automaton. spot::bdd_dict_ptr dict = spot::make_bdd_dict(); // This creates an empty automaton that we have yet to fill. spot::twa_graph_ptr aut = make_twa_graph(dict); // The current way to associate a BDD to an atomic proposition is // not really nice, and should be improved in the future. Currently // the string first have to be converted into (LTL) formulas... spot::ltl::environment& e = spot::ltl::default_environment::instance(); const spot::ltl::formula* f1 = e.require("p1"); const spot::ltl::formula* f2 = e.require("p2"); // ...and then those formula can be registered to the BDD dict. The // BDD dict wants to keep track of which automaton uses which BDD // variable, so we supply that pointer to aut. The // register_proposition() function returns a BDD variable number // that can be converted into a BDD using bdd_ithvar(). bdd p1 = bdd_ithvar(dict->register_proposition(f1, aut)); bdd p2 = bdd_ithvar(dict->register_proposition(f2, aut)); // Set the acceptance condition of the automaton to Inf(0)&Inf(1) aut->set_generalized_buchi(2); // States are numbered from 0. aut->new_states(3); // new_edge() takes 3 mandatory parameters: // source state, destination state, label // and a last optional parameter can be used // to specify membership to acceptance sets. aut->new_edge(0, 1, p1); aut->new_edge(1, 1, p1 & p2, {0}); aut->new_edge(1, 2, p2, {1}); aut->new_edge(2, 1, p1 | p2, {0, 1}); // Print the resulting automaton. print_hoa(std::cout, aut); return 0; }
HOA: v1 States: 3 Start: 0 AP: 2 "p1" "p2" acc-name: generalized-Buchi 2 Acceptance: 2 Inf(0)&Inf(1) properties: trans-labels explicit-labels trans-acc --BODY-- State: 0 [0] 1 State: 1 [0&1] 1 {0} [1] 2 {1} State: 2 [0 | 1] 1 {0 1} --END--