Prolog_Library

A minimal Prolog interpreter written in Haskell. Implements unification, clause interpretation with backtracking, fresh variable generation, cuts, and error reporting.

Build

cabal build

Run

cabal run prolog-library

Or with GHCi:

ghci src/Term.hs src/Unify.hs src/Interpret.hs src/Examples.hs

Modules

Module	Purpose
Term	Core types: Term, Clause, Prolog, Subst
Unify	Robinson unification and substitution
Interpret	Interpreter with backtracking and cuts
Examples	Genealogical tree database and sample queries
Tests	Unit tests for unification, substitution, and queries

Features

• Unification: standard Robinson unification with substitution
• Backtracking: depth-first search over the clause database
• Cuts (Cut): commits to the current clause, prevents backtracking
• Fresh variables: state-based alpha-conversion (no name collisions)
• Error reporting: Either String results with failure messages

Example

queryResult myExample (Func"pai" [Var"X", Atom"janeti"])
-- [("X","olicio")]

The myExample database models a family tree with progenitor, sexo, mae, and pai predicates.