Table of ContentsProlog and Logic Programming Relations Another relation Functions vs. Relations Prolog deals with relations Language metaphors Knuth on program correctness History of Prolog Not for general purpose programming Why restrict applicability of a language? Example applications Eight Queens: A typical search problem A Solution to Eight Queens Eight Queens in Prolog Query for solution A Prolog Program Example facts Queries Syntax for facts Variables Variables are scoped within a query More facts A simple rule Two interpretations of rule Predicate logic and English Implication Our friend the list Declaration of append rule “Return value” is an argument of the rule Terminology Lists Lists need not be homogeneous Unification of terms Unification of terms S and T More unification examples Unification is implicit in rule application Unification in append rule Trace of app([1,2,3],A,[1,2,3,4]) Trace of app([1,2,3],[4],Z) Arithmetic in Prolog Arithmetic only works forward in Prolog Constraint Logic Programming Importance of Constraint Logic Programming CLP(R) can do arithmetic in all directions! member rule Definition of member The declarative interpretation falls short… More uses of member How Prolog tries to prove Evidence of top to bottom rule order Order of rules matters! Trace of mem1(2,[1,2,3]) Trace of mem2(2,[1,2,3]) mem1 was faster PPT Slide PPT Slide PPT Slide PPT Slide Prolog is not an oracle! PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide Search algorithm Multiple sub-goals Another search tree… Tracing through the tree PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide PPT Slide Backtracking is not always what we want delete_all example A query for delete_all delete_all can succeed in any of three ways... delete_all has multiple matching rules Third rule contained implicit assumption Use a “cut” — ! The query again Cut divides problem into backtracking regions Controversy over cut cut and not !, fail combination Tree view of a cut Tree view of a cut Difference lists— an incomplete data structure Hole variables for accessing end of the list Appending elements to a difference list Unifications in dl_app Another way to query |
Author: Greg J. Badros
Email: badros@cs.washington.edu Home Page: http://www.cs.washington.edu/education/courses/341/CurrentQtr |