COMP 3007 Lecture Notes - Lecture 21: Backtracking, Birdwatching
26 Oct 2018
School
Department
Course
Professor
Document Summary
Use cut: cut commits the system to every choice it has made since it chose the rule, reason for cuts, 1. Faster execution, don"t spend time satisfying goals that can"t or don"t need to be satisfied: 2. Fewer backtrack points need to be considered, therefore less memory required. Confirmation of choice of rule: tell prolog it has found appropriate rule for a goal. e. g. , if you get this far, don"t try the other rules. sum_one_to(n,r). The sum of numbers from 1 to n is r. X = 15; false. sum_one_to(1,1):- !. sum_one_to(n, result):- Result is result1 + n: both rules are ok for sum_one_to(1,x). However, we do not want to use the second rule if n = 1: must tell prolog not to evaluate the second rule if the number n is 1. We do this by adding a cut: better solution would be to handle 0 or negative numbers: sum_one_to(n,1) :- n =< 1, !. sum_one_to(n, result) :-
