(Nils' Scheme Snippets)

(sum integer₁ integer₂) => integer

Purpose

Compute the sum of a range of integers.

Arguments

n	least integer in range
m	greatest integer in range

Example

(sum 8 10) => 27

(define (sum n m)
  (let ((x (+ 1 (- m n))))
    (+ (quotient (+ x (* x x))
                 2)
       (* x (- n 1)))))