language Essence 1.3 letting items be enum {a,b,c,d,e} letting capacity be 100 letting values be function ( a --> 10 , b --> 20 , c --> 40 , d --> 40 , e --> 50 ) letting weights be function ( a --> 15 , b --> 25 , c --> 45 , d --> 50 , e --> 60 )