Ethiopian multiplication: Difference between revisions

=={{header|Racket}}==

<lang Racket>

#lang racket

(define (halve i) (quotient i 2))

(define (double i) (* i 2))

;; `even?' is built-in

(define (ethiopian-multiply x y)

(cond [(zero? x) 0]

[(even? x) (ethiopian-multiply (halve x) (double y))]

[else (+ y (ethiopian-multiply (halve x) (double y)))]))

(ethiopian-multiply 17 34) ; -> 578

</lang>