:- module(contestlib,
	  [sublist/2,
	   write_elements/1,
	   writeN/2,
	   for/3,
	   numlist/3,
	   int_width/2,
	   write_int/2,
	   map/3]).

sublist([],[]).
sublist([X|R],[X|S]) :- sublist(R,S).
sublist([_|R],S) :- sublist(R,S).

write_elements([]).
write_elements([X|R]) :- write(X), write_elements(R).

writeN(N,C) :-
	( N > 0 ->
	    M is N - 1,
	    write(C),
	    writeN(M,C)
	;
	    true
	).

for(I,I,J) :- I =< J.
for(K,I,J) :- I < J,
	I1 is I + 1,
	for(K,I1,J).

numlist(I,J,List) :-
	( I =< J ->
	    List = [I|Rest],
	    I1 is I + 1,
	    numlist(I1,J,Rest)
	;
	    List = []
	).

int_width(N,Width) :-
	( N > 9 ->
	    M is N // 10,
	    int_width(M,WidthM),
	    Width is WidthM + 1
	;
	    Width = 1
	).

write_int(Int,Width) :-
	int_width(Int,WidthInt),
	Spaces is Width - WidthInt,
	writeN(Spaces,' '),
	write(Int).


map([],_,[]).
map([X|R],C,[CX|CR]) :-
	call(C,X,CX),
	map(R,C,CR).