Interpolation polymorphic example

interpolation.lgt

% use the apply module instead of the Logtalk meta
% library object to illustrate interoperability
:- use_module(library(apply)).
:- use_module(library(apply_macros)).


:- category(math).

	:- public(interpolate/4).
	interpolate(K1, X1, X2, Y) :-
		K2 is 1 - K1,
		::mul(K1, X1, KX1),
		::mul(K2, X2, KX2),
		::add(KX1, KX2, Y).

	:- protected([mul/3, add/3]).

:- end_category.


:- object(floats, imports(math)).

	add(X, Y, Z) :- Z is X + Y.

	mul(X, Y, Z) :- Z is X * Y.

:- end_object.


:- object(vector, imports(math)).

	add(X, Y, Z) :- apply:maplist(plus, X, Y, Z).

	plus(X, Y, Z) :- Z is X+Y.

	mul(X, Y, Z) :- apply:maplist(times(X), Y, Z).

	times(X, Y, Z) :- Z is X*Y.

:- end_object.


% sample calls:
%
% ?- floats::interpolate(0.2, 10, 20, F).
% F = 18.0.
%
% ?- vector::interpolate(0.2, [10,5,2], [20,30,10], V).
% V = [18.0, 25.0, 8.4].