- Prolog (Programming in Logic)
is a programming language based on
It uses the restricted syntax of Horn Clauses:
|Predicates, e.g., ||floats(), etc. |
|Operators ||<=, and, not |
|Logical variables ||X, GP, etc. |
|Constants ||7, girl, etc. |
|Function names ||f, left(), ... |
|Facts ||female(girl). |
|rules ||burns(X) <= wooden(X). |
|queries ||? witch(girl). |
- Quantification of logical variables is implicit --
universal for facts and rules,
existential for queries.
- The introduction will get you going and
there are more examples.
The interpreter shows how Prolog works.
- NB. The applet above needs Java on.
|<= (also :- )
||can be read as if, or as is implied by.
||can be read as ∀ P, P is a planet if P orbits the sun.
(That is not to say that the
definition cannot be tightened.)
||can be read as
does there exist an S such that S is a satellite?
|And the answer, here, is yes, if
S is earth's moon, or a moon of another planet.