Logic programming

1
Logic programming
2
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

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Brief history

• 1970s
• AI group
• To specifying predicate calculus
• Prolog

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Predicate calculus

• Proposition a logical statement that is true or
  not true
• Formal logic describes proposition that allows
  them to be checked or validity

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Logic Programming Example

• Suppose we have the following sentences
• CS student of NTHU must take the core course
  cs2403
• 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?

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• / 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).

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Logic Programming Prolog Query

• Queries
• ancestor(fred, sally).
• Yes
• ancestor(fred, diane).
• Yes
• ancestor(fred, bill).
• No

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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/prolo
  g-for-se.html
• http//www.swi-prolog.org/