(define mapper
  (lambda (key val)
    (emit-words (string-tokenize key))))

(define emit-words
  (lambda (words)
    (if (null? words) #f
        (begin
          (wmr-emit (car words) "1")
          (emit-words (cdr words))))))

(define reducer
  (lambda (key vals)
    (wmr-emit key (reduce-values 0 vals))))

(define reduce-values
  (lambda (sum vals)
    (if (stream-null? vals) sum
        (reduce-values (+ sum (string->number (stream-car vals)))
                       (stream-cdr vals)))))