nodouble and max

[Terry007]

hello I have two easy examples, but I'm greenhorn in prolog.

nodouble (x, list1, list2) - predicate delete duplicate values in List 1 and save them to List2

max (list, x) - predicate find max value from List and save it to X.

I find max from list as:
maxList([]).
maxList([E],E).
maxList([E,E2|T],L) :- maxList([E2|T],L1), max(L1,E,L).
but how to save it to x?

and for nodouble:
Dupli([],[]).
Dupli([X|Xs],[X,X|Ys]) :- dupli(Xs,Ys).
but it is not what I need..

 

[Terry007]

Now I need only one.. In second example - how to save duplicate values into List 2???

 

[kahleen]

maxList([E], E) :- !.
maxList([E|T], R) :-
maxList(T, X),
(E > X, !, R is E; R is X).

 

[kahleen]

% i don't understand why noDouble takes 3 arguments:
% noDouble(X, List1, List2) ????

noDouble([], []).
noDouble([E|T], R) :-
noDouble(T, R1),
(member(E, R1), !, R = R1; R = [E|R1]).

 

[joel76]

nodouble (x, list1, list2) - predicate delete duplicate values in List 1 and save them to List2
I suppose that it would be useful to have the list without duplicates ! nodouble(L, L1, L2) !

 

[joel76]

kahleen > your code doesn't save duplicates.

 

[kahleen]

my bad ... i read the specification superficially and the name nodouble also misled me ... this is exactly why i didn't see the point of it having 3 parameters

the simplest idea to solve that is this:

noDouble(L, L1, L2) :-
reverse(L, LR),
noDouble(LR, [], L1, [], L2).

noDouble([], L1, L1, L2, L2).
noDouble([E|T], L1P, L1, L2P, L2) :-
member(E, T), !,
(
member(E, L2P), !,
noDouble(T, L1P, L1, L2P, L2);
noDouble(T, L1P, L1, [E|L2P], L2)
).
noDouble([E|T], L1P, L1, L2P, L2) :-
member(E, L2P), !,
noDouble(T, L1P, L1, L2P, L2);
noDouble(T, [E|L1P], L1, L2P, L2).

joel, I didn't make heavy use of these forums, how do you make some text to represent code? are there some <code> code </code> marks available to use?

 

[kahleen]

i meant, the simplest idea that i had

 

[joel76]

are there some <code> code </code> marks

Yes, options are explained when you click on Preview Post
For code it's between [ code] [ /code] (I must put a space between '[' and 'c' of code !!)

 my code