chickadee » transducers » collect-mapping

Collects elements from a transduction into either a mapping or a hashmap with a given comparator. If no comparator is provided, the default comparator from SRFI-128 is used.

 
(import (only (srfi 128)
              make-default-comparator)
        (srfi 146 hash)
        transducers)

(define hm
  (transduce list-fold
             (zip-list (list 'alpha 'beta 'gamma))
             (collect-hashmap (make-default-comparator))
             (list "asdf" "foo" "bar")))

;; We convert to an alist here purely for the sake of demonstrating the inner values.
;;
;; Otherwise srfi-146 would just print something like #<srfi.146.hash#<hashmap>>
(hashmap->alist hm)

; => (("foo" . beta) ("bar" . gamma) ("asdf" . alpha))

Note that you may find that the ordering of the final alist in the above example doesn't match 1:1 with how that hashmap is traversed locally. That is because no order is specified or assumed.