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Associative array/Iteration: Difference between revisions
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(* in functional programming it is often more useful to fold over the elements *)
CharMap.fold (fun k v acc -> acc ^ Printf.sprintf "key: %c - value: %d\n" k v) map "Elements:\n" ;;</lang>
=={{header|Ol}}==
<lang ol>
;;; create sample associative array
(define aa (list->ff '(
(hello . 1)
(world . 2)
(! . 3))))
(print aa)
; ==> #((! . 3) (hello . 1) (world . 2))
;;; simplest iteration over all associative array (using ff-iter, lazy iterator)
(let loop ((kv (ff-iter aa)))
(cond
((null? kv) #true)
((pair? kv)
(print (car kv))
(loop (cdr kv)))
(else (loop (force kv)))))
; ==> (! . 3)
; ==> (hello . 1)
; ==> (world . 2)
;;; iteration with returning value (using ff-fold)
(print
"folding result: "
(ff-fold
(lambda (result key value)
(print "key: " key ", value: " value)
(+ result 1))
0
aa))
; ==> key: !, value: 3
; ==> key: hello, value: 1
; ==> key: world, value: 2
; ==> folding result: 3
;;; same but right fold (using ff-foldr)
(print
"rfolding result: "
(ff-foldr
(lambda (result key value)
(print "key: " key ", value: " value)
(+ result 1))
0
aa))
; ==> key: world, value: 2
; ==> key: hello, value: 1
; ==> key: !, value: 3
; ==> rfolding result: 3
;;; at least create new array from existing (let's multiply every value by value)
(define bb (ff-map aa
(lambda (key value)
(* value value))))
(print bb)
; ==> #((! . 9) (hello . 1) (world . 4))
</lang>
=={{header|ooRexx}}==
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