GRoutar
GRoutar

Reputation: 1425

Nth not recognized PROLOG

I've been dealing with lists in SICStus Prolog 4.3.0 (latest version) and I have the need to print an element of a list which Index is N.

I made some research and the predicate nth seemed to be the one:

nth0(?N, ?List, ?Elem) 

I gave it a go and tried it out but apparently the predicate is not recognized anywhere:

| ?- nth0(3, [a, b, c, d, e], Elem).
! Existence error in user:nth0/3
! procedure user:nth0/3 does not exist
! goal:  user:nth0(3,[a,b,c,d,e],_217)

Any suggestions on what is going on?

Edit: I looked up the documentation for SICStus 4.3.0 and the predicate does exist. It just won't be recognized.

Edit2: I tried adding the lists library : :- use_module(library(lists)). Still nothing.

Upvotes: 0

Views: 824

Answers (1)

GRoutar
GRoutar

Reputation: 1425

After some research I figured it out myself.

Edit2 was the answer, but it was not correctly implemented. It should be used as follows:

:- use_module(library(lists)).

Upvotes: 1

Related Questions