domains list=integer* predicates order(list) clauses order([X]). order([X,Y|Tail]):- X<=Y, order([Y|Tail]). OUT PUT ======= Goal: order([1,2,3,4]) Yes -------------------------- Goal: order([1,2,5,3]) No -------------------------- Goal: order([1,5,6,6,9]) Yes -------------------------- Goal: order([9,4,5]) No