nl_tokens: ### symmetricDifference * ( set1 set2 [ ... setN ] ) * The symmetric of two sets is is the set of elements in either set but not their intersection . If two sets are equal the symmetric difference is empty .
pl_tokens: function ( ) { return underscore . reduce ( arguments , function ( <mask> , second ) { return underscore . union ( underscore . difference ( first , second ) , underscore . difference ( second , first ) ) ; } ) ; }