Logic programming

Introduction To express program in symbolic logic Also called declarative language Only the specification of desired results are

stated State the form of the result rather than how a

result is to be computed Logic programming is a declarative approach of

writing computer programs based on Logic

Brief history

1970s AI group To specifying predicate calculus Prolog

Predicate calculus

Proposition: a logical statement that is true or not true

Formal logic describes proposition that allows them to be checked or validity

Logic Programming – Example

Suppose we have the following sentences

1. CS student of NTHU must take the core course cs2403

2. A CS student can not obtain a degree without passing the required course

I am a CS student of NTHU and want to obtain a degree, should I pass cs2403?

/* Filename: ancestor.pro This program creates a small set of facts and rules on

who is the ancestor of whom. The user types the desired goal interactively when the program is run.*/

/* ancestor(A, B) means A is an ancestor of B */ancestor(bob, susan).ancestor(A, X) :- parent(A, X).ancestor(A, X) :- parent(A, C), ancestor(C, X).

/* parent(P, C) means P is a parent of C */parent(fred, sally).parent(tina, sally).parent(sally, diane).parent(sam, bill).

Logic Programming – Prolog Query

Queries: ancestor(fred, sally).

Yes ancestor(fred, diane).

Yes ancestor(fred, bill).

No

Logic Programming – Reference

Book: Ralph P. Grimaldi, DISCRETE AND COMBINATORIAL

MATHEMATICS, 5TH ED, Pearson Education, 2004 Ulf Nilsson and Jan Ma luszy_nski, LOGIC, PROGRAMMING AND

PROLOG, 2ND ED, Ulf Nilsson and Jan Ma luszy_nski, 2000

Web: http://cis.stvincent.edu/carlsond/prolog.html http://ktiml.mff.cuni.cz/~bartak/prolog/index.html http://www.cs.auckland.ac.nz/~j-hamer/07.363/prolog-for-se.html http://www.swi-prolog.org/