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Egison Pattern Matching in Ruby - Express Intuition Directly with Essentially New Syntax - Vol.01　Sep/18/2014 Satoshi Egi Rakuten Institute of Technology http://rit.rakuten.co.jp/

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Self-Introduction

Name Satoshi Egi (江木聡志)

Association Rakuten Institute of Technology (楽天技術研究所)

Education Majored Computer Science in the University of Tokyo

Interests Programming Languages, AI (Mathematics)

Website http://www.egison.org/~egi/

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Very Quick Introduction of Today’s Contents

I have created the programming language that realized non-linear pattern-matching even against data that have no standard form.

(match-all xs (multiset integer) ! [<cons $x <cons ,x _>> x]) !Egison

Enumerate the elements of the collection ‘xs’ that appear

more than twice

pairs = [] !(1..n).each do |i| ! (i..n).each do |j| ! if xs[i] == xs[j] ! pairs = pairs + ! xs[i] ! end ! end !end !

Ruby

Non-linear patterns allow multiple occurrences of same variables in a pattern

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I have implemented the same feature in Ruby! The source code on GitHub!

match_all(xs) do ! with(Multiset.(_x,__x, *_)) { x } !end !Ruby with Egison gem

Enumerate the elements of the collection ‘xs’ that appear

more than twice

pairs = [] !(1..n).each do |i| ! (i..n).each do |j| ! if xs[i] == xs[j] ! pairs = pairs + ! xs[i] ! end ! end !end !

Ruby

https://github.com/egison/egison-ruby

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Poker hands analyzer with a single expression in Ruby!

Our pattern-matching expression represents all hands in a single pattern

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We can also pattern-match against infinite streams.

… , x, x + 2, …

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Source and English Document are on GitHub https://github.com/egison/egison-ruby

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Please Check My Blog Article, too

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We wrote also Japanese Documents on Qiita

1,0004 views, 185 Hatena Bookmarks!

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1. Introduction - What is Pattern Matching? 2. Egison Pattern Matching in Ruby 3. Let’s Try Egison Gem 4. Future Goal – Application of Egison

Table of Contents

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Table of Contents

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What is Pattern Matching?

A feature of programming languages that simplifies programs.

• Data Decomposition • Pattern-matching enables us to extract and

examine the value of an instance variable very easily

• Conditional Branches • Pattern-matching eliminates nested and

complex conditional branches

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Greeting Demonstration

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fail

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success

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Flow of Pattern Matching

fail

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success

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fail

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fail

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fail

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fail

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success

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Table of Contents

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The Features of Egison Pattern-Matching in Ruby

We have features in addition to simplification of data decomposition and conditional branches

• Customizable Way of Pattern-Matching • We can do pattern-matching against not only

fixed data such as lists but also multisets and sets that have multiple ways of decomposition

• Non-Linear Pattern-Matching • We allow multiple occurrences of same

variables in patterns • Pattern-Matching with Backtracking

• We allow multiple results of pattern-matching even infinite results

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Customizable Pattern Matching For Various Data

We can define how to pattern-match for each data types

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Pattern Matching with Multiple Results

We can handle multiple results of pattern-matching

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Element Patterns and Collection Patterns

A literal that starts with ‘_’ is a pattern-variable. We can refer the result of pattern-matching through them.

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A subcollection pattern matches the subcollection of the target array. A subcollection pattern starts with ‘*’.

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A literal that starts with ‘_’ is a pattern-variable. We can refer the result of pattern-matching through them.

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A subcollection pattern matches the subcollection of the target array. A subcollection pattern starts with ‘*’.

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Combinations with Pattern Matching

… , x, …, y, …

… , x, …, y, …, z, …

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Non-Linear Pattern Matching

A Pattern whose form is ‘__("...")’ is a value pattern

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Non-Linear Pattern Matching

A Pattern whose form is ‘__("...")’ is a value pattern

We can omit (“ and “) when enclosed with them is a single variable

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Poker Hands Analyzer in Ruby

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The Pattern for Straight Flash

Pattern for straight flash

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The Pattern for Straight Flash

Pattern for straight flash

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Same suit with $s

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Same suit with $s

We can write any expression after ‘__’

Numbers are serial from $n

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Pattern for two pairs

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The Pattern for Two Pairs


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Same number with $m

Same number with $n

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Same number with $m

Same number with $n

Non-linear patterns have very strong power

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Non-linear patterns enables to represent all hands in a single pattern

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We can also pattern-match against infinite streams.

… , x, x + 2, …

Pattern Matching against Streams with Infinite Results

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One More Interesting Demonstration

We can also enumerate prime triplets using and-patterns and or-patterns effectively.

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Table of Contents

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Egison Gem is on GitHub https://github.com/egison/egison-ruby

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Try Egison Gem!

$ git clone　https://github.com/egison/egison-ruby.git$ cd egison-ruby/$ bundle install$ make$ ls sample/… sample/poker_hands.rb …$ ruby sample/poker_hands.rb…

Egison Gem is written in pure Ruby. Installation is very easy via RubyGems.

We have prepared a lot of samples. Please try all of them.

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Table of Contents

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Introduction of the Egison Programming Language

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Profile of Egison

Paradigm Pattern-matching-oriented, Purely functional

Author Satoshi Egi

License MIT

Version 3.3.12 (2014/9/18)

First Released 2011/5/24

Filename Extension .egi

Implemented in Haskell (about 3,500 lines)

I have created Egison to represent human’s intuition directly.

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The Additional Features of Pure Egison

We have features in additon to simplification of data decomposition and conditional branches

• Ways of Pattern-Matching is More Customizable • We can customize the way of pattern-

matching against not only against collection such as lists, multisets and sets

• Pattern Modularization with Lexical Scoping • We allow multiple occurrences of same

variables in patterns

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More complex example, Mahjong

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Two same tiles

Three consecutive tiles

Three same tiles

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Two same tiles


Three same tiles

Seven twins or one twin + four shuntsu or kohtsu

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Two same tiles


Three same tiles

Seven twins or one twin + four shuntsu or kohtsu

Pattern modularization makes programming more simple!

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Egison on an online media

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Egison on Hacker News

Egison was actively discussed on Hacker News twice!

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Total session is 14,109

Access Map of the Website in This Half Year (2014/1/14 – 2014/7/14)

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Egison will be taught in the University of Tokyo by Prof. Hagiya

Egison will have big impact on the academic world, too!

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Growth of Community in This Year (2013/11/15 – 2014/9/18)

•  Mailing List Members •  Before: 12 – Only my friends •  Current: 23 – Communicating in English

•  Stargazers on GitHub •  Before: 12 – Only my friends •  Current: 214 – People from all over the world!

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My Mind Map on Programming Language

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Egison is pioneering this field!

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Application of Egison

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There is a Wide Range of Application

•  Daily programming •  Able to express complex tasks simply

•  Data access and analysis •  Work as the most elegant query language •  Able to access the wide range of data types in a

unified way •  Natural language processing

•  Able to handle complex structures intuitively as humans do in their mind

•  AI (Mathematical expression handling) •  Able to handle various mathematical and abstract

notions directly

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Query example

•  Query that returns twitter users who are followed by “__Egi” but not follow back “__Egi”.

id integer name string

User:

from_id integer to_id Integer

Follow:

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SQL version

•  Complex and difficult to understand •  Complex where clause contains “NOT EXIST” •  Subquery

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Egison version

•  Very Simple •  No where clauses •  No subquery

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Egison version

•  Very Simple •  No where clauses •  No subquery

Joining 4 tables

1. Get id of “__Egi” 2. Followed by ‘uid’ 3. But not follow back not 4. Get name of ‘fid’ Return the results

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My Dream

•  Daily programming •  Able to express complex tasks simply

•  Data access and analysis •  Work as the most elegant query language •  Able to access the wide range of data types in a

unified way •  Natural language processing

•  Able to handle complex structures intuitively as humans do in their mind

•  AI (Mathematical expression handling) •  Able to handle various mathematical and abstract

notions directly

•  Programs that find interesting things •  Programs that build math theories •  Programs that generate programs

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[ANN]Articles on Egison will be on CodeIQ MAGAZINE

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[ANN] We will post Egison problems on CodeIQ

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Thank you!

Please try Egison and give us feedback!

[email protected]

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Problem

What is the 40th pair of prime numbers of the form (p, p+8)?

Please try and answer to @Egison_Lang!

e.g.　[3, 11] [5, 13] [11, 19]…