Programming Languages: Concepts and Implementation

Chapter 14

Logic Programming

(1) No ducks waltz;

(2) No officers ever decline to waltz;

(3) All my poultry are ducks.¹

(1) Every one who is sane can do Logic;

(2) No lunatics are fit to serve on a jury;

(3) None of your sons can do Logic.²

(Sets of Concrete Propositions, proposed as Premisses for Soriteses: Conclusions to be found—in footnotes)

— Lewis Carroll, Symbolic Logic, Part I: Elementary (1896)

The more I think about language, the more it amazes me that people ever understand each other at all.

—Kurt Gödel

For now, what is important is not finding the answer, but looking for it.

—Douglas R. Hofstadter, Gödel, Escher, Bach: An Eternal Golden Braid (1979)

IN contrast to an imperative style of programming, where the programmer ...