I want to implement a predicate of the form:

zipwithindex(?List1, ?List2)

which is true when the elements of List2 are the same as in List1 but are paired with the index of the element.

This is what I have:

  I1 is I+1,

Is there a better way to implement this?


migrated from stackoverflow.com May 12 '14 at 13:53

This question came from our site for professional and enthusiast programmers.



zipwithindex(List1, List2) :-
   findall(E/I, nth0(I, List1, E), List2).

Edit - after Tudor' comment

bagof/3 it's much better than findall/3, as it doesn't introduce unwanted new variables. This can be of utmost importance when working with constrained variables - i.e. CLP(FD) or CHR

  • 3
    \$\begingroup\$ I would suggest bagof/3 instead of findall/3 in this case as, if there are unbound variables in List1, List2 will have new variables instead of the original ones. E.g. ?- zipwithindex([X,Y,Z],L2). will produce L2 = [_G41/0, _G35/1, _G29/2]. \$\endgroup\$ – Tudor Berariu Jun 9 '14 at 7:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.