%%=============================================================================
%%	 system configuration

config(WS,Full,Fix) :-
	abolish_all_tables,
	retractall(window_size(_)),
	retractall(seq(_)),
	retractall(fixed(_)),
	retractall(full(_)),
	S is 2*WS,
	assert(window_size(WS)),
	assert(seq(S)),
	assert(fixed(Fix)),
	assert(full(Full)).


%%=============================================================================
%%	Some arithmetic

:- import ground/1 from basics.

eval(X = Y)  :- !, X = Y.
eval(X == Y) :- !, eval(X, U), eval(Y, V), modulus(U, Ua), modulus(V, Va), Ua == Va.
eval(X := Y) :- !, eval(Y, U), modulus(U, X).
eval(X is Y) :- !, eval(Y, U), modulus(U, X).
eval(X > Y)  :- !, eval(X, U), eval(Y, V), modulus(U, Ua), modulus(V, Va), Ua > Va.
eval(X < Y)  :- !, eval(X, U), eval(Y, V), modulus(U, Ua), modulus(V, Va), Ua < Va.
eval(X >= Y) :- !, eval(X, U), eval(Y, V), modulus(U, Ua), modulus(V, Va), Ua >= Va.
eval(X =< Y) :- !, eval(X, U), eval(Y, V), modulus(U, Ua), modulus(V, Va), Ua =< Va.
eval(not(E)) :- !, not(eval(E)).

eval(A+B, V) :- !, eval(A, Va), eval(B, Vb), V is Va+Vb.
eval(A-B, V) :- !, eval(A, Va), eval(B, Vb), V is Va-Vb.
eval(A*B, V) :- !, eval(A, Va), eval(B, Vb), V is Va*Vb.
eval(A/B, V) :- !, eval(A, Va), eval(B, Vb), V is Va/Vb.
eval(A//B, V) :- !, eval(A, Va), eval(B, Vb), V is Va//Vb.
eval(hwin, V) :- !, window_size(V).
eval(qwin, V) :- !, window_size(W), V is W//2.
eval(E, V) :- V is E.

modulus(E, V) :- seq(Seq), X is E mod Seq, abs(X, V).
abs(X, V) :- ( X < 0 -> (seq(Seq), V is X+Seq) ; V = X).

%% Now, some interval stuff

in_interval(X, open(L,U)) :- 
	X =\= L,
	eval((L-X) =< hwin),
	eval((X-U) =< hwin).

in_open_interval(X, L,U) :- 
	X =\= L,
	eval((L-X) =< hwin),
	eval((X-U) =< hwin).

in_interval(X, upper_closed(L, U)) :-
	(L > U -> (X > L; X =< U)
		; (X > L, X =< U)).
in_interval(X, closed(L, U)) :-
	(L > U -> (X >= L; X =< U)
		; (X >= L, X =< U)).

% implement set as bit-string

in_set(Element, Set) :-
	1 is ((Set >> Element) mod 2).

add_to_set(Element, Set, NewSet) :- 
	in_set(Element, Set)
	->	NewSet = Set
	;	NewSet is Set + (1 << Element).

remove_from_set(Element, Set, NewSet) :-
	in_set(Element, Set)
	->	NewSet is Set - (1 << Element)
	;	NewSet = Set.

%%---------------------------------------------------------------------------
%%	internal procedure
do_exp(Tmp, RecSeq, Recbuf, NewRecSeq, NewRecbuf) :-
	in_set(Tmp, Recbuf)
	->	(remove_from_set(Tmp, Recbuf, Recbuf1),
		eval(T is Tmp+1),
		do_exp(T, Tmp, Recbuf1, NewRecSeq, NewRecbuf))
	;	(NewRecSeq = RecSeq ,
		NewRecbuf = Recbuf).