This is a basic implementation of a Prolog interpreter in OCaml with REPL support. The interpreter follows standard Prolog IO syntax where clauses, facts, rules and terms have their usual definition.

The implementation consists of a lexer lexer.mll, a parser parser.mly, an REP loop toyprolog.ml and the core unification and substitution engine tree.ml.

• The project contains a makefile that generates an executable toyprolog.
• The executable can be run as ./toyprolog inputfile where inputfile should contain all facts and rules to be loaded before execution.
• The project also contains a sample prolog script based on the Harry Potter universe family trees. Its called hogwarts.pl and contains lots of interesting facts and rules.
• NOTE: For obvious reasons the resolution search for queries is depth limited to 100 post which search will terminate.

make
./toyprolog hogwarts.pl
?-brother(X,ginnyWeasley).
X = ronWeasley;
X = georgeWeasley;
X = fredWeasley;
X = percyWeasley;
X = charlieWeasley;
X = billWeasley;
false.

?-ancestor(X,harryPotter).
X = doreaBlack;
X = charlusPotter;
X = violettaBulstrode;
X = cygnusBlack;
X = ursulaFlint;
X = phineasNigellusBlack;
X = lillyPotter;
X = jamesPotter;
false.