Good to know, thank you Ben :)
On Jan 13, 10:49 am, B Smith-Mannschott <bsmith.o...@gmail.com> wrote:
> On Thu, Jan 13, 2011 at 17:36, Benny Tsai <benny.t...@gmail.com> wrote:
> > (conj) will add items to different places in the collection, depending
> > on the type of the collection. For a set, this can be at either the
> > end OR the beginning.
>
> For a (hashed) set, this can be *anywhere* (between existing elements too).
>
> FTFY
>
> // Ben
>
>
>
>
>
>
>
> > For this problem, the output is built by:
>
> > (conj (conj (conj #{6857} 1471) 839) 71)
>
> > which is equivalent to:
>
> > (-> #{6857} (conj 1471) (conj 839) (conj 71))
>
> > The innermost/first conj, (conj #{6857} 1471), sticks 1471 at the end
> > and produces #{6857 1471}. The next conj sticks 839 at the beginning
> > and produces #{839 6857 1471}. The final conj sticks 71 at the
> > beginning and produces the final result of #{71 839 6857 1471}.
>
> > When ordering matters, I usually use either (cons), which will always
> > add to the beginning regardless of the collection type, or use (conj)
> > with a list (will always add to the beginning) or vector (will always
> > add to the end).
>
> > user=> (-> '(6857) (conj 1471) (conj 839) (conj 71))
> > (71 839 1471 6857)
> > user=> (-> [6857] (conj 1471) (conj 839) (conj 71))
> > [6857 1471 839 71]
>
> > On Jan 13, 8:09 am, Vitaly Peressada <vit...@ufairsoft.com> wrote:
> >> The following solution by <b>mtgred</b> for <a href="http://clojure-
> >> euler.wikispaces.com/">Project Euler Clojure</a> problem 003 uses
> >> implicit recursion.
>
> >> <pre>
> >> (use '[clojure.contrib.lazy-seqs :only (primes)])
> >> (defn prime-factors [n]
> >> (let [f (some #(if (= 0 (rem n %)) %) primes)]
> >> (if (= f n) #{f} (conj (prime-factors (/ n f)) f))))
> >> (apply max (prime-factors 600851475143))
> >> </pre>
>
> >> Here is above with added println
>
> >> (defn prime-factors [n]
> >> (let [f (some #(if (= 0 (rem n %)) %) primes)]
> >> (println "n:" n ", f:" f)
> >> (if (= f n)
> >> #{f}
> >> (conj (prime-factors (/ n f)) f))))
>
> >> Which produces
>
> >> n: 600851475143 , f: 71
> >> n: 8462696833 , f: 839
> >> n: 10086647 , f: 1471
> >> n: 6857 , f: 6857
> >> #{71 839 6857 1471}
>
> >> Can anybody explain why 6857 comes 3rd? I would expect to be the last.
>
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