Getting started
                                                                      • We’ll use SICStus Prolog
            Logic Programming                                            • Free for UofE students
                                                                         • Can request through Windows support
                     Lecture 1: Getting started                       • Available on all DICE machines
                                                                         • Tutorials, exams will be based on this version
                                                                      • Online documentation
                                                                         http://www.sics.se/isl/sicstuswww/site/index.html
                   Hello World                                                     Hello World
       • Prolog is an interactive language.                           • Prolog is an interactive language.
          $ sicstus                                                      $ sicstus
                                                                         ?- 
                   Hello World                                                   Hello World
       • Prolog is an interactive language.                          • Prolog is an interactive language.
          $ sicstusPrompt                                               $ sicstus
          ?-                                                            ?- print(’hello world’).
                   Hello World                                                   Hello World
       • Prolog is an interactive language.                          • Prolog is an interactive language.
          $ sicstus                            Goal                     $ sicstus
          ?- print(’hello world’).                                      ?- print(’hello world’).
                                                                        hello world
                                                                        yes
                   Hello World                                                   Hello World
       • Prolog is an interactive language.                          • Prolog is an interactive language.
          $ sicstus                                                     $ sicstus
          ?- print(’hello world’).                                      ?- print(’hello world’).
                                     Output                                                        Output
          hello world                                                   hello world
          yes                                                           yes
                                                                                    response
                         Atoms                                                      Variables
       • An atom is                                                  • A variable is a sequence of alphanumeric 
          • a sequence of alphanumeric characters                       characters
             • usually starting with lower case letter                  • usually starting with an uppercase letter 
          • or, a string enclosed in single quotes                   • Examples:
       • Examples:                                                      X  Y  Z  Parent Child Foo 
          homer   marge   lisa   bart
          ‘Mr. Burns’ ’Principal Skinner’
                       Predicates                                                        Predicates (2)
        • A predicate has the form                                             • Predicates have a name
                             p(t1,...,tn)                                        • = atom p in p(t1,...,tn)
           where p is an atom and t1...tn are terms                            • and an arity
           (For now a term is just an atom or variable)                          • = number of arguments (n)
        • Examples: 
                                                                               • Predicates with same name but different arity 
           father(homer, bart)                                                    are different
           mother(marge, bart)                                                 • We write foo/1, foo/2, ... to refer to these 
                                                                                  different predicates
                             Facts                                                                 Facts
           A fact is an assertion that a predicate is                           A fact is an assertion that a predicate is 
        •                                                                    •                                   Punctuation is 
           true:                                                                true:                              important!
           father(homer, bart).                                                 father(homer, bart).
           mother(marge, bart).                                                 mother(marge, bart).
        • A collection of facts is sometimes called a                        • A collection of facts is sometimes called a 
           knowledge base (or database).                                        knowledge base (or database).