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logic.js

////////////////////////////////////////////////////////////////////////////////
// Simple logic demo, no point in it. But just 'cuz.

var Unifier = require('./unifier.js');

var unify = Unifier.unify;
var parse = Unifier.parse;

/*****************************************************************************
 * A simple logic language querier.
 */
var search = exports.search = function(db,exprStr){
  var results = [], expr = parse(exprStr);
  db.map(function(entry){
    var result;
    try {
      if(typeof entry != 'string') {
        // First, ensure that the conclusion of the rule matches the
        // query.
        // E.g. Query: (Person a)
        //      Conclusion: (Person x)
        var conclusion = parse(entry[0]);
        unify({exp1:conclusion,exp2:expr});
        // Second, search for an instantiation of the rule's body in
        // the DB.
        var body = entry[1];
        var dbSansThisRule = db;
        queryResult = search(dbSansThisRule,body)[0];
        // Third, unify to get the /frame/ for the unification of the
        // body and the result.
        var frame;
        var bod = unify({exp1:queryResult,exp2:parse(body),returnFrame:true});
        // Finally, merely instantiate the conclusion against the
        // body's frame.
        result = unify({
          exp1:conclusion,exp2:conclusion,frame:bod.frame
        }).result;
      }
      else {
        result = unify({exp1:parse(entry),exp2:expr}).result;
      }
    } catch (e){
      return false;
    }
    results.push(result);
  });
  return results.length? results : 'No.';
}

// Example

// console.log(search([
//   'Programmer Foo',
//   ['MeetingsVisitor person','SupremeManager person']
//   'Programmer Bar',
//   'SupremeManager Mu',
//   'Programmer Zot'
// ],'MeetingsVisitor who'));