On Sun, Jan 11, 2009 at 9:35 PM, GS <gsincl...@gmail.com> wrote:
>
> Hi,
>
> For the purposes of testing another function (not discussed here), I
> wrote a function to generate random strings. This is what I ended up
> with after some trial and error.
>
> (defn generate-data [size maxlength]
> ; Returns a collection of 'size random strings, each at most 'maxlength
> chars.
> (let [alphabet "abcdefghijklmnopqrstuvwxyz"
> rand-letter (fn [_] (nth alphabet (rand-int 26)))
> rand-stream (map rand-letter (iterate inc 0))
> rand-string (fn [n] (apply str (take n rand-stream)))]
> (map (fn [_] (rand-string (rand-int maxlength)))
> (range size))))
>
> ; test
> (generate-data 25 19)
>
> The output of the testing function is something like ("gr", "gry",
> "gr", "g", "gry"). That is, is always _takes_ from the same sequence
> of random characters.
>
> Is there a way I might modify the above code so rand-stream is indeed
> a stream (with new random data each time) instead of a sequence (where
> every _take_ starts from the beginning)?
That generates a single rand-stream and then takes various amounts
from it in your 'map'. To get a new random sequence each time, you'd
have to move the definition of rand-stream into your 'map' fn so that
each item of the map gets its own random stream.
Here's one way to do that:
(defn generate-data [size maxlength]
(for [i (range size)]
(apply str (take (rand-int maxlength)
(repeatedly #(char (+ (int \a) (rand-int 26))))))))
But since this is returning a lazy stream (as your original did),
there's not much value in passing in the size:
(defn seq-of-rand-strings [maxlength]
(repeatedly (fn []
(apply str (take (rand-int maxlength)
(repeatedly #(char (+ (int \a) (rand-int 26)))))))))
user=> (take 3 (seq-of-rand-strings 10))
("kae" "xwuwyp" "xa")
--Chouser
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