Prolog has its roots in first-order logic, a formal logic, and unlike many other programming languages, Prolog is declarative: the program logic is expressed in terms of relations, represented as facts and rules. A computation is initiated by running a query over these relations.
Anyway I just learnt that I should know this language within two days so let us try.
Hello world, because traditions and stuff:
% This is a comment! printHelloWorld :- write('Hello world !'), nl. /* And these... ... are comments as well. */
Funny thing every line finishes with a PUNKT.
Prolog is dynamically typed (aka I don’t care of my variables’ type), with a single data type, the term. Subtypes: Atom (e.g. , x, ‘stuff’, ‘other stuff’, …), numbers, variables, and compound (aka « functions »). Variables start with a capital letter constants with a lower case letter.
Prolog works with clauses. There are two kind of clauses, rules and facts
Rule: Head is TRUE if Body is TRUE.
Head :- Body.
Fact: a Head with a Body always TRUE.