List length 2

Determining the length of a list.

Source: The Art of Prolog

Program source code: list_length_2.pl

/*
	mylength(Xs,N) :- The list Xs has N elements.
*/
 
	mylength([],0).
	mylength([X|Xs],s(N)) :- mylength(Xs,N).
 
%	Program 3.17: Determining the length of a list