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hy everyone, for homework i had to make a faculty function that used multiplication.
so i made this :
(define (fac a)
(if (= a 1)
(* a (fac (- a 1)))))
and it works, but the solution gave this :
(define (fac n)
(product (lambda (x) x) 1 (lambda (x) (+ x 1)) n))
and i dont understand what happens here, could someone explain for me?
many thanks, a beginning student
- Posts: 4
- Joined: Thu Oct 10, 2013 6:45 am
Obviously the product
takes 4 arguments an expression
, a lower bound
, an incrementor
and an upper bound
. And it works just like a mathematics big pi notation
. In this particular usage the expression
is an identity function (it's returning the index), the lower bound
is 1, the incrementor
is a function incrementing by 1 and finally the upper bound
- Posts: 198
- Joined: Thu May 10, 2012 12:54 pm
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