How to resolve the algorithm Harshad or Niven series step by step in the Prolog programming language

Published on 12 May 2024 09:40 PM
#Prolog

How to resolve the algorithm Harshad or Niven series step by step in the Prolog programming language

Table of Contents

Problem Statement

The Harshad or Niven numbers are positive integers ≥ 1 that are divisible by the sum of their digits. For example,   42   is a Harshad number as   42   is divisible by   (4 + 2)   without remainder. Assume that the series is defined as the numbers in increasing order.

The task is to create a function/method/procedure to generate successive members of the Harshad sequence. Use it to:

Show your output here.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Harshad or Niven series step by step in the Prolog programming language

Source code in the prolog programming language

:- use_module(library(lambda)).

niven :-
	nb_setval(go, 1),

	L = [1 | _],
	print_niven(L, 1),
	gen_niven(1, L).


print_niven([X|T], N) :-
	when(ground(X),
	     (	 (   nb_getval(go, 1)
		 ->  (   N < 20
		     ->  writeln(X),
			 N1 is N+1,
			 print_niven(T, N1)
		     ;	 (   X > 1000
			 ->  writeln(X),
			     nb_setval(go, 0)
			 ;   N1 is N+1,
			     print_niven(T, N1)))
		 ;   true))).



gen_niven(X, [N | T]) :-
	(   nb_getval(go, 1)
	->  X1 is X+1,
	    sum_of_digit(X, S),
	    (   X mod S =:= 0
	    ->  N = X,
		gen_niven(X1, T)
	    ;	gen_niven(X1, [N | T]))
	;   true).


sum_of_digit(N, S) :-
	number_chars(N, LC),
	maplist(\X^Y^number_chars(Y, [X]), LC, LN),
	sum_list(LN, S).

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