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This slide is presented at RubyKaigi 2014 on Sep 18. We have designed and implemented the library that realizes non-linear pattern matching against unfree data types. We can directly express pattern-matching against lists, multisets, and sets using this library. The library is already released via RubyGems.org as one of gems. The expressive power of this gem derives from the theory behind the Egison programming language and is so strong that we can write poker-hands analyzer in a single pattern matching expression. This is impossible even in any other state-of-the-art programming language. Pattern matching is one of the most important features of programming language for intuitive representation of algorithms. Our library simplifies code by replacing not only complex conditional branches but also nested loops with an intuitive pattern-matching expression.
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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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Very Quick Introduction of Today’s Contents
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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Very Quick Introduction of Today’s Contents
Poker hands analyzer with a single expression in Ruby!
Our pattern-matching expression represents all hands in a single pattern
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Very Quick Introduction of Today’s Contents
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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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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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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Greeting Demonstration
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Greeting Demonstration
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Greeting Demonstration
fail
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Greeting Demonstration
success
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Greeting Demonstration
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Flow of Pattern Matching
fail
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Flow of Pattern Matching
success
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Greeting Demonstration
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Flow of Pattern Matching
fail
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Flow of Pattern Matching
fail
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Flow of Pattern Matching
fail
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Flow of Pattern Matching
fail
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Flow of Pattern Matching
success
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Greeting Demonstration
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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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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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Element Patterns and Collection Patterns
A subcollection pattern matches the subcollection of the target array. A subcollection pattern starts with ‘*’.
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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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Element Patterns and Collection Patterns
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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Poker Hands Analyzer in Ruby
Same suit with $s
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Poker Hands Analyzer in Ruby
Same suit with $s
We can write any expression after ‘__’
Numbers are serial from $n
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Poker Hands Analyzer in Ruby
Pattern for two pairs
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The Pattern for Two Pairs
Pattern for two pairs
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The Pattern for Two Pairs
Pattern for two pairs
Same number with $m
Same number with $n
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The Pattern for Two Pairs
Pattern for two pairs
Same number with $m
Same number with $n
Non-linear patterns have very strong power
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Poker Hands Analyzer in Ruby
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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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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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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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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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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More complex example, Mahjong
Two same tiles
Three consecutive tiles
Three same tiles
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More complex example, Mahjong
Two same tiles
Three consecutive tiles
Three same tiles
Seven twins or one twin + four shuntsu or kohtsu
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More complex example, Mahjong
Two same tiles
Three consecutive 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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My Mind Map on Programming Language
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My Mind Map on Programming Language
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!
satoshi.egi@mail.rakuten.com
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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]…
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