public static boolean isIndempotent ( Map < Variable , Variable > substitutionMap ) { if ( substitutionMap . isEmpty ( ) ) return true ; Set < Variable > valueSet = new HashSet <> ( substitutionMap . values ( ) ) ; valueSet . retainAll ( substitutionMap . entrySet ( ) ) ; return valueSet . isEmpty ( ) ; }
Returns true if there is common variables in the domain and the range of the substitution map .