Logic

Overview

Logic provides a Prolog-style DSL for logic programming in Ruby.

require 'logic'
database = Logic.new
database.tell {
    mouse 'mickey'
    mouse 'minie'
    funny 'mickey'
    funny_mouse(:who) do
        mouse :who
        funny :who
    end
    love('minie', :x) { funny_mouse :x }
}

database.ask { love 'minie', :who } 

Outputs:

=>
:who = 'mickey';

Get Started

require "logic" in your project or irb (Logic needs Ruby 2.0+), then create a database by database = Logic.new. You are now ready to input data and query them.

Input

Entering data into the database is by providing a block to the tell method. Like Prolog, Logic supports two data types: fact and rule.
Fact: Logic use a method call and its arguments to represent Fact in Prolog.

database.tell { salary 'Ben', 1000 }

Rule: Rule in Prolog has a head and body. Logic uses a method call and a block following it to represent head and body respectively.

database.tell do
    rich(:x) { salary :x, 1000 }
end

Variable: Logic use Symbol to represent variable in Prolog. The rule above states ":x is rich if the salary of :x is 1000". You can create compound rule that has multiple requirements.

database.tell do
    super_rich(:x) do
        salary :x, 1000
        has_a_dog :x
    end
end

This states ":x is super_rich if the salary of :x is 1000 and :x has_a_dog"

Query

Querying the data entered so far is by providing a block to the ask method.

database.ask { rich 'Ben' }

Outputs:

=>
Yes

Again, Symbol is treated as variable.

database.ask { salary 'Ben', :x }

Output:

=>
:x = 1000;

That's it!

Feel free to play with it. If you have improvement idea, please let me know or send me a pull request.