After PhillyETE, I wanted to try out some Clojure, so I decided to solve the first problem of Project Euler. I coded up my own solution using some of the references on the Clojure site.

Project Euler Problem Description, from Project Euler

Find the sum of all the multiples of 3 or 5 below N. (N is 1000 is this Project Euler problem.)

Solutions

My first attempt

    (def nmbrs (range 0 1000))
    (def multiples
        (filter
            #(and
                (not= % 0)
                (or
                    (=
                        (rem % 3)
                        0
                        )
                    (=
                        (rem % 5)
                        0
                        )
                    )
                )
            nmbrs
            )
        )
    (reduce + multiples)

Another attempt by a different author

Afterwards, I came across a terser, more elegant solution on a site that seems to have had the same idea as I did, Learning Clojure with Project Euler. The site had a really elegant looking solution:

    ; //grok-code.com/367/learning-clojure-with-project-euler/
    (defn problem01 [limit]
     (reduce + (filter #(or (zero? (mod % 3))
                            (zero? (mod % 5)))
                       (take (- limit 1) (iterate inc 1)))))
    (problem 1000)

My revised attempt

The use of take and iterate are really interesting. I haven’t encountered these “lazy” functions, and was surprised when I tried to run (iterate inc 1) in the REPL. I decided to modify my version with some of the things I learned from the version above, and make it more terse.

    (defn problem01 
        [upper]
        (reduce +
            (filter
                #(or 
                    (zero?(rem % 3)) 
                    (zero?(rem % 5))
                    )
                (range 1 upper)
                ))
        )

I’ll be working on some more of the problems in the coming days.

(PS. If you are wondering why I use rem instead of mod, it’s because I am using an older version of clojure with TextMate–I’ve yet to upgrade)