/* A small (gnu) prolog example on 
   emotional modeling                            */

/* Timo Honkela, UIAH Media Lab, Nov 11, 1999    */

/* Based on the scheme presented at
   http://www.brunel.ac.uk/~hsstbbp/emotlec6.htm */

/* Save the files example1.pro to example4.pro into your working directory.

   Start gnu prolog environment:

      mlab > gprolog

   Load the example:

      ?- [example1].

   Set level of activation: 

      ?- set_a(0.8).

   Set level of pleansantness: 
   
      ?- set_p(-1.0).

   Query the state:

      ?- state(Name, Level).

   Input semicolon (;) for several answers: there should be three different
   states with varying levels of strenth.

   You can experiment by setting different levels of
   activation and pleasantness.

*/


/* ======= */
/* PROGRAM */
/* ======= */


/* The user sets the level of pleasantness of the agent */

set_p(Value) :-
	Value > 1.0,
	write('Please give values between -1 and 1\n'), !, fail.
set_p(Value) :-
	Value < -1.0,
	write('Please give values between -1 and 1\n'), !, fail.

set_p(Value) :-
	retract(pleasantness(_)), !,   /* if old value exists, retracted */
	asserta(pleasantness(Value)).  /* new value is set */
set_p(Value) :-
	asserta(pleasantness(Value)).  


/* The user sets the level of activation of the agent */

set_a(Value) :-
	Value > 1.0,
	write('Please give values between -1 and 1\n'), !, fail.
set_a(Value) :-
	Value < -1.0,
	write('Please give values between -1 and 1\n'), !, fail.

set_a(Value) :-
	retract(activation(_)), !,
	asserta(activation(Value)).
set_a(Value) :-
	asserta(activation(Value)).


/* State is computed.                                      */
/* The calculations are approximate, i.e., not following
   in detail the "emotion circle"                          */

state(stimulated, Z) :-
	pleasantness(P),
	activation(A),
	absolutevalue(P, AbsP),
	A > (AbsP / 2),
	Z is A - (AbsP / 2).
state(euphoric, Z) :-
	pleasantness(P),
	activation(A),
	A > 0,
	P > 0,
	Z is (A + P) / 2.0.
state(happy, Z) :-
	pleasantness(P),
	activation(A),
	absolutevalue(A, AbsA),
	P > (AbsA / 2),
	Z is P - (AbsA / 2).
state(serene, Z) :-
	pleasantness(P),
	activation(A),
	A < 0,
	P > 0,
	Z is (P - A) / 2.0.
state(passive, Z) :-
	pleasantness(P),
	activation(A),
	absolutevalue(P, AbsP),
	A < -1 * (AbsP / 2),
	Z is (-1 * A) - (AbsP / 2).
state(bored, Z) :-
	pleasantness(P),
	activation(A),
	A < 0,
	P < 0,
	Z is ((-1 * P) - A) / 2.0.
state(sad, Z) :-
	pleasantness(P),
	activation(A),
	absolutevalue(A, AbsA),
	P < -1 * (AbsA / 2),
	Z is (-1 * P) - (AbsA / 2).
state(anxious, Z) :-
	pleasantness(P),
	activation(A),
	A > 0,
	P < 0,
	Z is (A - P) / 2.0.
state(_,_).


/* calculate the absolute value           */
/* e.g. if X = -2.3 then AbsX becomes 2.3 */

absolutevalue(X, AbsX) :-
	X < 0,
	AbsX is -1 * X, !.
absolutevalue(X, X).