PlayerID{{
        public int compareTo(PlayerID pid)
        { return ((Integer)id).compareTo(pid.id); }
}}

Var{{
        public int compareTo(Var v)
        { return id.compareTo(v.id); }
}}

Solution{{ }}
Challenge{{ }}
         
OfferedChallenge{{ }}
AcceptedChallenge{{ }}
ProvidedChallenge{{ }}
SolvedChallenge{{ }}

Problem{{
        /** Implicit Variable List */
        public Problem(List<Clause> cs)
        { this(setOfVars(cs).toList(), cs); }
        /** Collect all the (distinct) Variables in a List of Clauses */
        private static Set<Var> setOfVars(List<Clause> cs){
            return cs.fold(new List.Fold<Clause,Set<Var>>(){
                    public Set<Var> fold(Clause c, Set<Var> r)
                    { return r.union(Set.create(c.getVars())); }
                }, Set.<Var>create());
        }
}}
Clause{{
        public List<Var> getVars(){ return vars; }
}}
ProblemType{{ }}


Objective{{
        double value(Problem inst, Solution sol);
}}
Predicate{{
        boolean valid(Problem inst, ProblemType pred);
}}