Using the printlist/1 predicate in Prolog to sum up all numbers in a list -

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i trying use printlist/1 predicate sum numbers in list kind of got stuck.... tried come code keep getting false.

here i've come with:

printlist([]). printlist([h|t], totalsum) :-     print (h+totalsum),    nl,    printlist(t, totalsum).

i know it's wrong , it's last part. appreciated!

i query way: 

?- printlist([1,2,3]). false.

as paulo said, defining 2 predicates here, incorrect.

here solution:

printlist([], 0). printlist([h|t], sum) :-    printlist(t, subsum),    sum subsum + h.

sample query:

?- printlist([1,2,3,5], l). l = 11.

@ paulo requested), tail recursive version:

printlist(l, sum) :-    sumac(l, 0, sum).  sumac([], acc, acc). sumac([h|t], acc, sum) :-    nacc acc + h,    sumac(t, nacc, sum).

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