13. Misc topics

Today's topics

Extreme programming

Human as programming resource

Callback programming and thread programming

Extreme Programming (XP)

Proposed by Kent Beck

Practical programming method

Kent Beck

Object-oriented programming professional

Author of Smalltalk books

http://gyazo.com/90e878e7e3991568c575010daaa2c06a.png

Basics

Communication

Simplicity

Feedback

Courage

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XP practices

Repetitive development

Design / implementation / test for each iteration

Release partially-completed producdt

Unit-based implementation

Repetition of code modification and testing

XP practices (Cont'd)

Use common words

Open development space

Easy conversation

Development practice

Test-driven development

Pair programming

Refactoring

Source code sharing

Continuous integration tests

YAGNI

Test-driven development

Write test codes before writing codes

Goal is to write codes which satisfy the tests

Clear goal and simple implementation

Pair programming

https://gyazo.com/735c1c0f9df0486fc392e9d22a0089a3.png

Two person share a terminal and write code

One writes the code

The other check the coding and navigate

Roles changes

Always codes are checked

Keep concenterated

Good for code sharing

Refactoring

Modify working codes

Change codes without changing specs

Strict test environment necessary

Sharing codes

Anyone in the team can modify codes

Everyone is responsible for the codes

Continuous integration (CI)

Always run integration tests after unit tests

Integration test at least onece a day

CI tools

Travis CI

Circle CI

Jenkins

YAGNI

Implement the minimal code

Don't implement features for the future

Implement only necessary codes

Easy to adapt to future spec changes

Programmers and XP

Many programmers liked the idea

Source codes are more important than documents

Small improvements more important than long-term visions

Program testing

http://gyazo.com/5e7a7dba9271d9217245911b716ceb45.png

Test-first programming

Write test codes at the beginning

Write codes after writing test codes

Go to next step if test was okay

Test-Driven Development (TDD)

Test-Driven Development

1. Write test codes before production

2. Write codes which satisfy test conditions

3. Modify codes and repet checking (Refactoring)

4. GOTO 1

Caveats

Programmers may write insufficient tests

Testers and programmers should be different

Test systems

Unit test frameworks

SUnit (Smalltalk)

JUnit (Java)

RubyUnit (Ruby)

RubyUnit

Test system for Ruby

Use assertions

Initial operations

Termination operations

RubyUnit example

code:test.rb

require 'test/unit'

class ArrayTest < Test::Unit::TestCase

def setup

@empty_array = []

end

def test_empty?

assert(@empty_array.empty?)

end

def test_size

assert_equal(0, @empty_array.size)

end

def teardown

@empty_array = nil

end

end

RSpec example

code:rspec.rb

describe Array, "when empty" do

before do

@empty_array = []

end

it "should be empty" do

@empty_array.should be_empty

end

it "should size 0" do

@empty_array.size.should == 0

end

after do

@empty_array = nil

end

end

JUnit example

code:junit.java

import static org.junit.Assert.*;

import org.junit.Test;

import static org.hamcrest.MatcherAssert.assertThat;

import static org.hamcrest.Matchers.*;

import com.pitecan.gyaim.GoogleIME;

import com.pitecan.gyaim.Message;

public class GoogleIMETest {

String 変換例リスト[][] = {

{"べんきょう", "勉強"},

{"ますい", "増井"},

{"いちのもと", "櫟本"},

{"むさしぼうべんけい","武蔵坊弁慶"},

{"かまくらのかいがん", "鎌倉の海岸"}

};

@Test

public void Google変換チェック() {

for (String[] 変換例: 変換例リスト) {

boolean found = false;

}

assertTrue(found);

}

}

}

Demo: Running tests for Gyaim

Pair programming

Two programmers use one computer

Develop a software together

Complementary roles

e.g. writing test codes and implementation

Advantages

Difficult to be idle

Higher quality expected than single person

Work flow change

Not worry about what to do next

Become tolerant to noises

Changing roles => changing thinking patterns

Advantages (Cont'd)

Some people like working together

Sharing codes

Education effect

Knowledges easily share bay the team

Teamwork

Less interruption

Difficult to interrupt two working person

Less number of computers

Results

Accuracy imprved 15%

Speed improved 20-40%

Total improvement 15-60%

...

Problems

Boring for experienced programmers

Some people hate working together

Efficiency not always improved

Talent unbalance

Coding style conflict

Scheduling

Remote working impossible

Problems

Difficult to have rests

Get tired

Refactoring

Changing codes with same spec

No rigid definition

Refactoring techniques

Extract methods and reuse

Change bidirectional relations to unidirectional

Create small classes

Change switch statement to polymorphism

Clean up class members

Refactoring techniques

Replace subclass with delegation

Encapsulate Downcast

Convert constructors to factory methods

Use objects for arguments

Change names and attributes

70 refactoring methods

http://gyazo.com/ffd3c3be1c703b3daed32ad82e4a451f.png

Test should be complete

Changing code is okay as long as testing done

Design pattern

Catalog of software know-how

"Gang of Four" book

23 patterns listed

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Patterns on generation

Abstract Factory パターン

関連する一連のインスタンスを状況に応じて適切に生成する方法を提供

Builder パターン

複合化されたインスタンスの生成過程を隠蔽

Factory Method パターン

実際に生成されるインスタンスに依存しない、インスタンスの生成方法を提供

Prototype パターン

同様のインスタンスを生成するために、原型のインスタンスを複製

Singleton パターン

あるクラスについて、インスタンスが単一であることを保証

Patterns on structure

Adapter パターン

元々関連性のない2つのクラスを接続するクラスを作る

Bridge パターン

クラスなどの実装と、呼出し側の間の橋渡しをするクラスを用意し、実装を隠蔽

Composite パターン

再帰的な構造を表現

Decorator パターン

あるインスタンスに対し、動的に付加機能を追加する。Filterとも呼ばれる。

Facade パターン

複数のサブシステムの窓口となる共通のインタフェースを提供

Flyweight パターン

多数のインスタンスを共有し、インスタンスの構築のための負荷を減らす

Proxy パターン

共通のインタフェースをもつインスタンスを内包し、利用者からのアクセスを代理する。Wrapperとも呼ばれる。

Patterns on behavior

Chain of Responsibility パターン

イベントの送受信を行う複数のオブジェクトを鎖状につなぎ、それらの間をイベントが渡されてゆくようにする。

Command パターン

複数の異なる操作について、それぞれに対応するオブジェクトを用意し、オブジェクトを切り替えることで操作の切替えを実現する。

Interpreter パターン

構文解析のために、文法規則を反映するクラス構造を作る。

Iterator パターン

複数の要素を内包するオブジェクトのすべての要素に順にアクセスする方法を提供する。反復子。

Mediator パターン

オブジェクト間の相互作用を仲介するオブジェクトを定義し、オブジェクト間の結合度を低くする。

Memento パターン

データ構造に対する一連の操作のそれぞれを記録しておき、以前の状態の復帰または操作の再現が行えるようにする。

Observer パターン

インスタンスの変化を他のインスタンスから監視できるようにする。Listenerとも呼ばれる。

State パターン

オブジェクトの状態を変化させることで、処理内容を変えられるようにする。

Strategy パターン

データ構造に対して適用する一連のアルゴリズムをカプセル化し、アルゴリズムの切替えを容易にする。

Template Method パターン

あるアルゴリズムの途中経過で必要な処理を抽象メソッドに委ね、その実装を変えることで処理が変えられるようにする。

Visitor パターン

データ構造を保持するクラスと、それに対して処理を行うクラスを分離する。

XP and pattern language

Close relationship

Kent Beck invented XP and pattern language

Christopher Alexander

Invented "Pattern Language"

http://gyazo.com/835dfec1ee8d66545ff1cd4933cfe488.png]

Ward Canninghum

Invented Wiki Wiki Web

Applied pattern language to software

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Human-powered programming

Human as programming resource

Human power is the ultimate computing resource

Some problems are solved only by humans

Which restaurant is the best

Interesting books?

Using human power for programming

Pair programming

Programming collective intelligence

Merging human power and computing power

Web = platform for using human power

Super parallel computingn by humans

Ultimate computing resource

Explicit human programming

Want to calculate complicated things

⇒ Create a service for gathering info

⇒ Get info from gathered data

Examples of human-powered calculation

Find a good restaurant

Find a influential person

Calculate the beauty of a lady

...

Calculation without notice

People often do something without notice

Boast about something

Correct something

Calculation with joy

Wikipedia

Hotornot

Kotonoha

reCAPTCHA

Wikipedia

World-biggest human calculation project

Calculate how beautiful a person is

http://gyazo.com/2dc0aa135251d5ad4f74c1b9a610c2f2.png

Simple inquiry

http://gyazo.com/d9f0658089b8e185d3005eca5d9f90b4.png

CAPTCHA

Prove that the user is a human

http://gyazo.com/d200e187b92f98e4d639ed8d23d5203f.png

reCAPTCHA

Authentication and character recognition

Not really interesting, though

http://gyazo.com/7c26209860f904a1feff6ca10d0aa073.png

Fixing something without notice

Correcting something if inappropriate

Picking up trash

Power of Low Standards

http://gyazo.com/c9147cba2b040dd25331909d064c0fa5.png

Location registration

Feel uneasy when registration is wrong

http://gyazo.com/bb7642f350fff42abb9f7a61bf31657b.png

After correction

Correct location registered

http://gyazo.com/61289b265ca621d8f77db568c2110c81.png

Feeling uneasy if text is incorrect

Want to fix it

Using curiocity

Mutual proofreading

http://gyazo.com/aa5264fa4e48875c793a1cf9b26e0379.png

Diary example

http://gyazo.com/97901c841fc693ae6d51ce1bac74d54b.png

BabaScript

Explicit human programming

Treat computers and humans the same way

Humans work as computing resources

List of instructions

Sample instruction

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Script for creating pasta

Instructions for humans are written in JavaScript

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Application

http://gyazo.com/e6e0d85e04cf4f6e6ed94cccd49d3de0.png

Receiving a request

Select one and reply

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Data mining from shared data

Programming collective intelligence

http://gyazo.com/3cfa17df5e77ccc67b7bd5f8f6a8279f.png

Programming collective intelligence

Recommendation systems

Clustering

Decision tree

SVM

Recommendation systems

Collaborative Filtering

e.g. Firefly

Firefly

Register musics you like

Recommend musics based on the data

Registration takes time

Last.fm

Preferences accumulated

No need for manual registration

Extract information from hondana.org data

Invoke methods in Japanese

Various calculation

Visualization by Hayashi's quantification method

Callback programming

Asynchronous programming

Became popular on JavaScript

Run heavy process later

Normal programming

code:funcs.js

func1();

func2();

func3();

Browser stalls

Solutions

Parallel programming

Callback programming

Example of callback programming

code:callback.js

func1();

func2(arg1,arg2,function()｛

// heavy or slow operations

// e.g. communication with slow server

console.log("end")

});

func3();

Calculation in background

"end" printed after calculation

Advantages of callback programming

Users should not wait termination

Pseudo parallel programming

Disadvantages of callback programming

Difficult to understand

Process ordering not guaranteed

Guaranteed execution order

Callback nesting

Difficult to understand deep nesting

"Callback hell"

code:async1.js

setTimeout(function(){

console.log('First');

setTimeout(function(){

console.log('Second');

setTimeout(function(){

console.log('Third');

},100);

},500);

},1000);

Guaranteed execution order

Use special libraries

async.js

Parallel/sequential execution

Async library

code:async2.js

var async = require('async');

async.series([

function (callback) {

console.log('series 1');

setTimeout(function () {

console.log('series 1 done.');

callback(null, 1);

}, 500);

},

function (callback) {

console.log('series 2');

setTimeout(function () {

console.log('series 2 done.');

callback(null, 2);

}, 300);

},

function (callback) {

console.log('series 3');

setTimeout(function () {

console.log('series 3 done.');

callback(null, 3);

}, 100);

}

], function (err, results) {

if (err) { throw err; }

console.log('series all done. ' + results);

});

Problems of using libraries

Extra specification

Difficult to handle errors

Explicit parallelism might be better

New feature of JavaScript

Handle asynchronus processing easily

Promise

Abstraction of asynchronous operation

Conventional callback

code:callback.js

getAsync("fileA.txt", function(error, result){

if(error){

// do error handling

throw error;

}

// process the result

});

code:promise.js

var promise = getAsyncPromise("fileA.txt");

promise.then(function(result){

// process the result

}).catch(function(error){

// error handling

});

Async-await

Use Promise for synchronous operations

code:async.js

function openFile(url) {

const p = new Promise((resolve, reject) => {

const xhr = new XMLHttpRequest();

xhr.open('GET', url);

xhr.addEventListener('load', (e) => resolve(xhr));

xhr.send();

});

return p;

}

async function loadAllFiles() {

const xhr1 = await openFile('foo.txt');

const xhr2 = await openFile('bar.txt');

const xhr3 = await openFile('baz.txt');

console.log('done!');

}

loadAllFiles();

Future of parallel programming

Semaphores, monitors are not convenient

Callback programming is difficult

History of loop processing

Old loop programs

Many GOTO statements

"spaghetti programming"

http://gyazo.com/ba6a0d78000d76428b935d3a1d63c4af.png

Criticism on GOTO statement

Proposed 'structured programing'

Structured programming

Restrict program structure

while, if, etc.

GOTO considered harmful

NS chart

http://gyazo.com/82bd29da9867ec20105a3d7de374441d.png

PAD

http://gyazo.com/127b8cf6de5ffa9915efb63ba2a95520.png

http://gyazo.com/7e50d657a9eade1a7af627a4315fd9c0.png

HCP chart

http://gyazo.com/b220896bd7c83977b8a3afa3bd2fdc37.png

Invention of for statement

for(init;cond;change)

Intruduced in C

Everything related to loop is in one line

Less bugs

XXcharts became extinct

e.g. while statement

code:while.txt

init

while(condition)｛

(Do something)

change values

}

Removing loops

map function

Apply a function to all elements

No loop statment

map function

code:map.rb

map.rb

puts s

}

Object-oriented programming

History of object-oriented programming

Simula

Smalltalk

C with classes

C++

Objective-C

Modula2

Eiffel

History of objected-oriented programing

Popular since 1980s

Common knowledge these days

Simula

Simulation language

Information hiding

Smalltalk

Developed at PARC

Integration with GUI

ALTO = GUI + OO + network

C++

"C with classes"

Was a front-end processor for C

Very popular

Objective-C

Developed by Brad Cox

http://www.amazon.com/dp/0201548348/ http://gyazo.com/f1929fecb1b6ec2f3e36a10633cbda1c.png

Objective-C

Smalltalk-like extention of C

Used for NeXT workstation

Used for Apple products

Modula2

Developed by DEC

Eiffel

Bertrand Myer

http://gyazo.com/04acd02b4fb4ea7e46c55c3a64c945b3.png

Method call and member access looks the same

Adopted by various recent languages

JavaScript

Prototype-based OO

Widely used recently

Many "ALT-JS"

CoffeeScript

Typescript

Prototype-based OO

Use existing object as 'prototype'

Proposed in the 80s

Essence of OO

Inheritance?

Information hiding?

Data sharing?

Mapping between real objects and computer objects?

Distributed communication?

Essence of OO

Technique for making programs shorter (Prof. Takeuchi)

Is OO really needed?

OO-like programming possible on C

Not as important as structured programming and recursion?

Unix kernel is not implemented in OO language

Compilers are not implemented in OO language

OO thinking

File system and OO

Japanese and OO

File system and OO

No distinction between file and I/O device

/home/masui/xxx (file) and /dev/xxxx (I/O) are treated as the same

Article by Nakajima-san

"Salt to me"

Not "pass me the salt"

Merits of postfix notation

X.inv.log

log(inv(X))

Conclusions

Various programming pradigms

Enjoy programming anywhere!