Reduce is a function or method that is used to take the values in an array or a list and apply a function to successive members of the list to produce (or reduce them to), a single value.



Task

Show how reduce (or foldl or foldr etc), work (or would be implemented) in your language.



See also

 Wikipedia article:   Fold
 Wikipedia article:   Catamorphism


(define (reduce fn init lst)
  (do ((val init (fn (car rem) val)) ; accumulated value passed as second argument
       (rem lst (cdr rem)))
    ((null? rem) val)))
 
(display (reduce + 0 '(1 2 3 4 5))) (newline) ; => 15
(display (reduce expt 2 '(3 4))) (newline)    ; => 262144