On Jan 15, 1:21 pm, Nicolas Buduroi <nbudu...@gmail.com> wrote:
> Hi, I'm still not familiar with laziness and I'm trying to make a
> function recursively walk arbitrary data structures to perform some
> action on all strings.
> ...
> Is there a way too make a fully lazy version of this function?
>
> - budu
I'm trying to create a lazy version of walk. Here's my first attempt:
(defn lazy-walk
"Traverses form, an arbitrary data structure. inner and outer are
functions. Applies inner to each element of form, building up a
data structure of the same type, then applies outer to the result.
Recognizes all Clojure data structures except sorted-map-by."
[inner outer form]
(lazy-seq
(cond
(list? form) (outer (apply list (map inner form)))
(seq? form) (outer (map inner form))
(vector? form) (outer (vec (map inner form)))
(map? form) (outer (into (if (sorted? form) (sorted-map) {})
(map inner form)))
(set? form) (outer (into (if (sorted? form) (sorted-set) #{})
(map inner form)))
:else (outer form) ) )
)
user=> (def lw (lazy-walk #(if (string? %) (.toUpperCase %) %)
identity (interleave (repeat
10000 88) (repeat 10000 "abc"))))
user=> (type lw)
clojure.lang.LazySeq
user=> (take 20 lw)
(88 "ABC" 88 "ABC" 88 "ABC" 88 "ABC" 88 "ABC" 88 "ABC" 88 "ABC" 88
"ABC" 88 "ABC" 88 "ABC")
I'm still not quite sure how to test lazy functions for correct lazy
behavior, though.
regards,
-tom
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