noahlz

;; "Find the sum of all the multiples of 3 or 5 below 1000."

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Filtering
;; "Create a divides? predicate that takes a dividend and a divisor, and returns true if divisor evenly 
;; divides the dividend"

;; My solution to the filtering "divides?" problem:

(defn divides? [num div] (= 0 (mod num div)))

noahlz

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Atoms

;; Using swap! and merge-with on a map
;; the trick is to put merge-with inside a function.

(def m (atom {:a 1}))
;=> #'user/m

user> (swap! m #(merge-with + % {:a 2}))

noahlz

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; 3.2 Nil pun with care

(defn print-seq [s]
  (when (seq s)
     (prn (first s))
     (recur (rest s))))
;; #'user/print-seq

(print-seq [1 2])

noahlz

(re-find #"A|B|C" "B") ;; Two Problems
;=> "B"

(some #(= % "B") ["A" "B" "C"]) ;; A little better...but not the same
;=> true

(get #{ "A" "B" "C"} "B") ;; more readable?
;=> "B"

(#{"A" "B" "C"} "B") ;; Idiomatic per Joy of Clojure

noahlz

(ns joy.q)
;; nil

(defn nom [n] (take n (repeatedly #(rand-int n))))
;; #'joy.q/nom

(defn sort-parts [work]
     (lazy-seq
      (loop [[part & parts] work]            ;; Pull apart work - note: work will be a list of lists.
        (if-let [[pivot & xs] (seq part)]    ;; This blows up unless work was a list of lists.

noahlz

;; Example of using comp
(map (comp keyword #(.toLowerCase %) name) '(a B C))
;=> (:a :b :c)

;; equpivalent code using -> (but which doesn't use functions as data.
(map #(-> % (name) (.toLowerCase) (keyword)) '[a B C])
;=> (:a :b :c)


;; Using partial

noahlz

import java.util.Random;
import java.util.concurrent.*;

/**
 * App that tests completion service.
 */
public class CompletionServiceExample {

    private static final int COUNT = 25;

noahlz

package com.transacttools.imaginary;

import com.transacttools.imaginary.util.ActionUtils;
import java.util.Date;
import java.text.SimpleDateFormat;

/**
 * This class processes actions from the User Interface.
 *
 * TODO: Get this ready for production!

noahlz

#include <stdio.h>

// see http://stackoverflow.com/a/7943955/7507

int main(int argc, char *argv[]) {

    int bestSoFar = 0;
    int bestNow = 0;
    int bestStartIndexSoFar = -1;
    int bestStopIndexSoFar = -1;

noahlz

(defn factorial-using-recur [x]
  (loop [current x
         next (dec current)
         total 1]
    (if (> current 1)
      (recur next (dec next) (* total current))
      total)))

(defn factorial-using-reduce [x]
  (reduce * (range 1 (inc x))))