Please help with Prolog examples

[mrtommy]

Hello... I really need help with these examples... Thank You...

1) sum (List, X)

Predicate stored in the variable X total value of all elements of list List.


2) double (List, ListList)

Predicate stored in the variable ListList list where each list element List occurs twice in a row.

 

[joel76]

What did you try ?

 

[mrtommy]

I have this for first example and I don´t know if is it right...


sum([],0).
sum([H | T], S) :-
integer(H),
sum(T, S1),
S is S1 + H.

 

[joel76]

It looks correct.

 

[mrtommy]

Fine... That´s great... Thank You... But I don´t know, how to do second example... I really need help... I have a exam on friday...

 

[mrtommy]

Is that correct?

?- dupli([a,b,c],2,X).
X = [a,a,b,b,c,c,]

 

[mrtommy]

Or this is correct? Pleas reply...


double([],[]).
double([H|T],[H,H|Y]) :- double(T,Y).

 

[joel76]

double([],[]).
double([H|T],[H,H|Y]) :- double(T,Y).

This is correct.