On 4 February 2010 09:04, Wardrop <t...@tomwardrop.com> wrote:
> I often myself creating functions which perform a rather clear and
> simple task, but which is hard to describe, either because I don't
> know the term for what I've just implemented, or because the function
> is difficult to summarise in a couple of words. As an example, I've
> just created a function which determines how many times the value n,
> can be divided by the base, until n becomes smaller than the base.
> Here's the implementation...
>
> (defn <insert-name-here> [n base]
> (loop [n n count 0]
> (if (< n base)
> {:val n :count count}
> (recur (float (/ n base)) (inc count)))))
>
> This can be used among other things, to determine how to format bytes.
> Say I have a file that's 6,789,354 bytes, and I want to display that
> in a more readable manner, I could use my unnamed function like so
> (<unnamed> 6789354 1024), and get a new appropriately rounded number,
> including the number of times it has been rounded, which I can use the
> pick the appropriate suffix from a list ("Bytes", "KB", "MB", "GB",
> "TB).
I would probably split that up:
The division can just use /, so no need for a separate function.
The rest can be done like this:
(defn logn [n x]
(/ (java.lang.Math/log x) (java.lang.Math/log n)))
Then you could have a function that formats file sizes:
(defn format-file-size [num-bytes]
(let [base 1024
val (float (/ num-bytes base))
times (int (logn base num-bytes))]
...)
Not sure if that helps with your general question, though :)
> I mean, what the hell would you name this function, or would you not
> create such an obscure and generalised function to start with?
--
Michael Wood <esiot...@gmail.com>
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