Haskellog

Simple Prolog interpreter written in Haskell

Hello!

This is an university project made in Haskell for Functional programming course.

Supported:

• Constants*
• Rules and facts**
• Infinite generation

*Only atom constants are supported. Lists, numbers and aritmetic operations and not yet implemented.

**Rules only support logical AND via "," in their body.

How to use:

• Load Main module into GHCi and run main function by typing "main" in *Main> prompt
• Load .pl file with valid Prolog code by entering its full path when prompted
  • You are now inside a Read Evaluate Print Loop (REPL) made for this version of Prolog.
  • The prompt of this REPL is *Haskellog>
• Enter commands inside *Haskellog> prompt.

Supported commands

• *Haskellog> :help

  • Get a list of supported commands.

• *Haskellog> ??

  • Get a list of all rules and facts. Prints the current state of the knowledge base.

• *Haskellog> blue(sky).

  • Adds fact "blue(sky)." to knowledge base.

• *Haskellog> p(X, Y) :- q(X, Z), r(Z, Y).

  • Adds rule "p(X,Y):-q(X,Z),r(Z,Y)." to knowledge base.

• *Haskellog> ?- p(X, Y).

  • Make a query. To get more answers enter ";". Enter anything else (for example ".") to stop.

• *Haskellog> ?- q1(X, Y, Z), q2(Y), q3(T).

  • Make multiple queries at once connected with logical AND similar to a rules body.

• *Haskellog> :q

  • Quit interactive loop (exits out of *Haskellog> prompt).

Please reload Main module (*Main> :r) before running main function again after *Haskellog> :q

Sources and inspirations for code and approach

• Basic Parser module idea: https://www.youtube.com/watch?v=cdHY9Kqfr-k
• Ideas for rest of the modules: https://github.com/propella/prolog/
  • Credit goes to Takashi Yamamiya: https://github.com/propella/