===========
 Star Trek
===========

/* facts */
outranks(picard, riker).
outranks(riker, worf).
outranks(riker, geordi).
outranks(geordi, wesley).

/* rules */
commands(X, Y) :- outranks(X, Y).
commands(X, Y) :- outranks(X, Z), 
                  commands(Z, Y).
/*
queries:
commands(picard, X).
commands(riker, X).
*/



======================
 Simple Type Checking
======================

/* Facts */
type(i, int).
type(j, int).
type(k, int).
type(x, real).
type(y, real).

/* Rules */
expectedtype(plus(E1,E2),T) :- type(E1,T), 
                               type(E2,T).
/* Queries
 * 
 * type(i, X)
 * type(x, X)
 * 
 * // Type Checking
 * expectedtype(plus(i,x),int)
 * expectedtype(plus(i,x),real)
 * expectedtype(plus(i,i),int)
 * expectedtype(plus(x,x),real)
 * expectedtype(plus(i,j),int)
 *
 * // Type Inference
 * expectedtype(plus(i,j),X)
 * expectedtype(plus(x,y),X)
 * expectedtype(plus(i,y),X)
 * expectedtype(plus(i,X),int)
 * expectedtype(plus(i,X),real) 
 * expectedtype(plus(X,Y),int)
 * expectedtype(plus(X,Y),real) 
 */