Noah Zucker noahlz

Organizing Clojure Projects

Stuart presented using a deck created with org-html-slideshow, a Clojure library for formatting org-mode notes as HTML slides.

General Code Structure / Organization

Be careful not to make function calls across component boundaries.
Protocols should be minimalistic. They should have the fundamental operations of your component.

Bush league is a general term used to describe an action or thing as being amateur, inferior or crude. In a literal sense, it refers to a low quality minor-league in baseball not associated with any of the major league teams. The term originated from the state of minor-league fields that often were ringed with shrubs and bushes.

- Wikipedia

Secretly using StringBuffer to convert a number to a String

int value = getValue();
String valStr = value + "";

	;; Solve the problem "find the set of characters two strings have in common"

	;; Approach #1 BitSets
	;; - use a bitsets for each string,
	;; - flip the bit for each character in each string
	;; - then "and" the two bitsets. Theoretically O(N + M) performance

	(defn string-to-charbits [s]
	(loop [[f & rest] s
	bits (java.util.BitSet.)]

	#!/bin/sh

	# Futile attempts keep BUG below to not potentially exit the script.
	set +e +E
	trap '' ERR

	# displays the prompt in light cyan.
	# TODO: http://stackoverflow.com/q/6788777/7507

	echo -e "\e[00;36mEnter expressions, [Ctrl-C] to exit\e[00m"

	;; adopted from http://www.datomic.com/company/resources/getting-started
	;; Clojure 1.4.0

	;; user=>
	(use '[datomic.api :only [q db] :as d])
	;;=> nil

	;; user=>
	(doc d/q)
	;; -------------------------

	;; Robot from Joy of Clojure, Ch 7

	(def bearings [{:x 0 :y 1} ; move north
	{:x 1 :y 0} ; move east
	{:x 0 :y -1} ; move south
	{:x -1 :y 0}]) ; move west
	(defn bot [x y bearing-num]
	{:coords [x y]
	:bearing ([:north :east :south :west] bearing-num)
	:forward (fn [] (bot (+ x (:x (bearings bearing-num)))

	;; See http://stackoverflow.com/questions/12066020/in-clojure-why-i-need-to-write-doc-str-but-meta-str

	;; Define a var foo that points to a function
	(def foo (with-meta (fn [] (println "bar")) {:doc "prints bar"} ))
	;=> #'user/foo
	(foo)
	;=> bar
	;=> nil

	;; We see the :doc in our foo metadata...but where's our REPL documentation?


	import java.io.*;
	import java.util.concurrent.atomic.AtomicInteger;

	/**
	* http://stackoverflow.com/q/12321837/7507
	*/
	public class GetLatestBuildNumber {

	private static final AtomicInteger number = new AtomicInteger();

	;; See https://twitter.com/stevelosh/status/269269366992936960

	(defn multi-update [m updates]
	(reduce (fn [m [k f & args]]
	(update-in m k #(apply f % args)))
	m updates))

	;; user=> (multi-update {:a 1 :b 2 :c 3} [[[:a] 1 1 1][[:b] 1 1][[:c] 3 1 -2]])
	;; {:a 4, :c 5, :b 4}

	public Result processCommand(Data data) {
	try {
	return doStuff();
	// fuck it, just catch everything
	} catch (Exception ex) {
	String message = ex.getMessage() != null ? message : "LOL OOPS!";
	return new Result(message);
	}
	}