chickadee » foof-loop » MULTIPLYING

Usage:

   (FOR <result> (SUMMING [(INITIAL <initial-sum>)] ...))
   (FOR <result> (MULTIPLYING [(INITIAL <initial-product>)] ...))

Accumulates sums or products by adding the accumulated data to <initial-sum>, or multiplying the accumulated data by <initial-product>.

<Initial-sum> and <initial-product>, if supplied, must be numbers, and are evaluated once before the loop begins. The default value of <initial-sum> is 0, and the default value of <initial-product> is 1.

<Result> is a loop variable.

   (define (count predicate list)
     (loop ((for elt (in-list list))
            (for count (summing 1 (if (predicate elt)))))
       => count))