Question

i have a problem
i take in input a list, and i want append it’s element to another that i want in output

this is my code :

run([],L).
run([X|Y],Lista) :- X =..Total, append(Total,Lista,ListaR), run(Y,ListaR), stamp(ListaR).

stamp([]).
stamp([X|Y]) :- nl, write(X), stamp(Y).

if I run it with:

run([p(X,Y,Z),h(Z,P,Q)],[]).

it will print out:

h
_G238
_G244
_G245
p
_G236
_G237
_G238
p
_G236
_G237
_G238
true.

why it contain 2 time the p ? what is wrong?

_GXXX are variables…

Answer 1

It prints p twice, because you print the result at each level of recursion. If you want to print it only once at the end, do so:

run([],L) :- stamp(L).
run([X|Y],Lista) :- X =..Total, append(Total,Lista,ListaR), run(Y,ListaR).