How to use recursion to sum/add the number between x and y?

Question

I would like to ask as to how would you be able to make a recursion that would add from your starting number (x) up to the end (y).

E.G. = summation(Ans, 1, 5). Ans = 15

(1+2+3+4+5) = 15 //is what should occur in the recursion

So far what I've done is this:

sumFrom(Sum, X ,Y) :- X>Y, !, write('Start should not be greater than End').
sumFrom(Sum, X ,Y) :- Sum is X+Y,
        Next is X+1,
        sumFrom(Sum, Next, Y).

I am still new to prolog so please be gentle.

Answer 1

Since pure (the declarative subset of) Prolog doesn't have loops and mutable variables, performing arithmetic can be tricky. I think it's worth to learn about libraries, when the basic has become clear:

?- aggregate(sum(N),between(1,5,N),S).
S = 15.