Prolog (Programming in Logic) is a logic programming language based on formal logic. Created by Alain Colmerauer, it allows programmers to express problems as logical relations, with the computer determining how to solve them.
Origins
Colmerauer developed Prolog at the University of Aix-Marseille in 1972, building on work in automatic theorem proving. The goal was to create a practical programming language based on first-order logic.
Key Concepts
Prolog uses a different paradigm from conventional languages:
- Declarative: Describe what, not how
- Unification: Pattern matching between terms
- Backtracking: Automatic search through possibilities
- Horn clauses: Logical statements as facts and rules
- Query-based: Pose questions the system answers
How It Works
In Prolog, you define facts and rules:
parent(tom, mary).— Tom is a parent of Marygrandparent(X, Z) :- parent(X, Y), parent(Y, Z).— X is a grandparent of Z if…
Then query: ?- grandparent(tom, Who).
Impact
Prolog influenced computing significantly:
- Expert systems: Dominant in early AI applications
- Natural language processing: Pattern matching for language
- Datalog: Query language for databases
- Constraint logic programming: Extensions for optimization
- Fifth Generation Computing: Japan’s 1980s AI initiative