This code looks it working:
(defn prime-2? [num]
(loop [i 2]
(if (<= (* i i) num)
(if (zero? (mod num i))
false
(recur (inc i)))
true)))
Any potential logic error?
On Feb 17, 2:01 am, Marek Stępniowski <mstepniow...@gmail.com> wrote:
> On Thu, Feb 17, 2011 at 12:34 AM, HB <hubaghd...@gmail.com> wrote:
> > I'm trying to write a function that determines if a number is a prime
> > or not.
> > Here is my first shot:
>
> > (defn prime? [num]
> > (loop [i 2]
> > (if (<= (* i i) num)
> > false)
> > (recur (inc i)))
> > true)
>
> > It is not working to be sure :)
>
> > Please blow my mind with various implementations.
>
> It seems that you're mixing loop expression in Clojure with a Java
> loop. The loop in Clojure is just a binding and a point to which each
> recur will jump, instead of the start of function. You're lacking a
> stop condition in the loop.
>
> Here is the solution similiar to yours, but with a proper accumulator
> and stop condition:
>
> (defn prime? [n]
> (let [m (Math/sqrt n))]
> (loop [k 2]
> (cond
> (> k m) true
> (zero? (mod n k)) false
> true (recur (inc k))))))
>
> IMHO more idiomatic Clojure solution, using seq operations:
>
> (defn prime? [n]
> (if (< n 2)
> false
> (not-any? #(zero? (rem n %))
> (range 2 (min (inc (Math/sqrt n)) n)))))
>
> Cheers,
> --
> Marek Stępniowskihttp://stepniowski.com
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