Should I avoid tail recursion in Prolog and in general?

Question

I\'m working through \"Learn Prolog now\" online book for fun.

I\'m trying to write a predicate that goes through each member of a list and adds one to it, using acc

Answer 1

In contrast to so some other programming languages, certain Prolog implementations are well suited for tail recursive programs. Tail recursion can be handled as a special case of last call optimization (LCO). For example this here in Java doesn't work:

public static boolean count(int n) {
    if (n == 0) {
        return true;
    } else {
        return count(n-1);
    }
}

public static void main(String[] args) {
    System.out.println("count(1000)="+count(1000));
    System.out.println("count(1000000)="+count(1000000));
}

The result will be:

count(1000)=true
Exception in thread "main" java.lang.StackOverflowError
    at protect.Count.count(Count.java:9)
    at protect.Count.count(Count.java:9)

On the other hand major Prolog implementations don't have any problem with it:

 ?- [user].
 count(0) :- !.
 count(N) :- M is N-1, count(M).
 ^D

The result will be:

?- count(1000).
true.
?- count(1000000).
true.

The reason Prolog systems can do that, is that their execution is most often anyway trampolin style, and last call optimization is then a matter of choice point elimination and environment trimming. Environment trimming was already documented in early WAM.

But yes, debugging might be a problem.