Prolog - Lecture 1

Prolog:

• Two types of statements:
• Rules
• Propositions
• File extension: .pl (just like Perl)
• Periods end statements.
• Avoid using spaces in code with the "gprolog" interpreter/compiler (GNU Prolog 1.2.16).
• This compiler is very user-unfriendly.
• Capital letters are "variables".
• At the interpreter prompt, type "[X]." to load and compile a file named X.pl. Do not type "[X.pl].".
• Type "trace." to enable trace mode, which will display the steps done by the interpreter.
• Type "notrace." to turn off trace mode.
  

With this file:

likes(jake,chocolate).
likes(jake,apricots).
likes(darcie,licorice).
likes(darcie,apricots).

Output of "likes(X,chocolate).":
 X = jake ? ; (it waits for command here:
   ; to show next solution, a for all solutions,  to stop)
 no

comma (",") is an "and" operator.
Output of "likes(darcie,X),likes(jake,X).":
 X = apricots
 yes

----
grandmother(X,Y):-mother(X,Z),mother(Z,Y).
grandmother(X,Y):-mother(X,Z),father(Z,Y).
mother(anna,peter).
mother(anna,clara).
mother(mary,anna).
father(joe,peter).
father(jim,clara).
father(tom,joe).

The "grandmother" statements are a propositions. ":-" means "implies".

grandmother(X,peter).
 X = mary ? ;
 no