% Allow singleton vars:
:-style_check(-singleton).

% Allow numbers to be changed -- shuffled
:-dynamic(number/2).

% ------generate sample of N lottery picks
sample(N) :-
	for(I, N),
	pick,
	fail.
sample(N).

% -------- The picked numbers are the first 6 numbers.
show_pick :-
	for(I, 6),
	number(I, P),
	(P < 10 , write('   ') ;  P >= 10 , write('  ')),
	write(P),
	fail.
show_pick :- nl,nl.

% --------number(I,J) stores a permutation of 1..50, See Botting 74.
number(33, 43).
number(26, 17).
number(40, 19).
number(48, 49).
number(24, 22).
number(9, 24).
number(25, 20).
number(17, 5).
number(41, 9).
number(16, 11).
number(7, 38).
number(22, 45).
number(12, 27).
number(20, 29).
number(29, 28).
number(38, 6).
number(11, 15).
number(47, 13).
number(18, 48).
number(37, 2).
number(46, 14).
number(14, 26).
number(28, 16).
number(49, 21).
number(34, 3).
number(19, 1).
number(13, 10).
number(50, 23).
number(21, 41).
number(32, 7).
number(30, 46).
number(44, 31).
number(39, 33).
number(35, 36).
number(8, 12).
number(36, 32).
number(42, 8).
number(15, 30).
number(1, 4).
number(27, 25).
number(2, 47).
number(45, 42).
number(3, 34).
number(43, 44).
number(4, 18).
number(10, 37).
number(5, 39).
number(31, 35).
number(6, 40).
number(23, 50).

% -------pick Californian ticket -------
pick :-
	shuffle,
	!,
	sort,
	!,
	show_pick,
	!.

% -------setup an initial datbase, in case it got corrupted.
setup :-
	abolish(number,2),
	for(I, 50),
	assert(number(I, I)),
	fail.
% ---- exchange to items in number
swap(I, J) :-
	I=J,!.
swap(I,J):-
	retract(number(I, A)),
	retract(number(J, B)),
	assert(number(I, B)),
	assert(number(J, A)),
	!.
% ---- prolog's for loop
for(I, I, N) :- I =< N.
for(I, M, N) :-
	M < N,
	M1 is M + 1,
	for(I, M1, N).
for(I, N) :- for(I, 1, N).

% How to shuffle the numbers
shuffle :-
	for(I, 6),
	shuffle(I),
	fail.
shuffle :- true.
shuffle(I) :-
	 J is random( 50)+1,
	swap(I, J),
	!.

% How to sort the first 6 numbers
sort:-
	for(I,5),K is 6-I,
	pass(I,K),
	fail.
sort:-true.
% I'th pass throught the 6 numbers in the sort.
% I is lint left in for debugging purposes
pass(I,K):- for(J,1,K),
	J1 is J+1,
	number(J,N),number(J1,N1),
	order(J,N,J1,N1),
	fail.
pass(I,K):-true.

% Put a pair of numbers into order
order(J,N,J1,N1):-
	(N=<N1
	; swap(J,J1)
	),!.
:- write('To generate a pick: pick. To sample N: sample(N).'), nl.