The Hamster Gem - Ryan Mulligan

Transcript

1. 1.

   “Efficient, immutable, and thread-safe collection classes for Ruby.” the hamster

   gem
2. 2.

   “Efficient, immutable, and thread-safe collection classes for Ruby.”

3. 3.

   “Efficient, immutable, and thread-safe collection classes for Ruby.”

4. 4.

   containers for objects

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   tuple (1, 2, 3)

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   set {1, 2, 3}

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   hash {:name => "James", :gender => :male}

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   vector (like array) [1, 2, 3, 4, 5]

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   stack User:Boivie http://en.wikipedia.org/wiki/Stack_(abstract_data_type)#mediaviewer/File:Data_stack.svg

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    queue User:Vegpuff on wikipedia http://en.wikipedia.org/wiki/Queue_(abstract_data_type)#mediaviewer/File:Data_Queue.svg

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    (linked) list

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    “Efficient, immutable, and thread-safe collection classes for Ruby.”

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    immutability

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    require "hamster" person = Hamster.hash(:name => "Simon", :gender => :male)

    person[:name] # => "Simon" friend = person.put(:name, "James") # => {:name => "James", :gender => :male} male = person.delete(:name) # => {:gender => :male} person # => {:name => "Simon", :gender => :male} male.key?(:name) # => false
15. 15.

    the sales pitch

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    immutability is a good thing™

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    Mutable stateful objects are the new spaghetti code: - hard

    to understand, test, reason about - Concurrency disaster Rich Hickey - Clojure “
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    Immutable objects are simple. Classes should be immutable unless there’s

    a very good reason to make them mutable. If a class cannot be made immutable, limit its mutability as much as possible. Josh Bloch, in Effective Java “
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    you are using immutable data

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    git, bitcoin blockchain, :ruby

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    benefits readability concurrency (thread-safety)

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    “Efficient, immutable, and thread-safe collection classes for Ruby.”

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    person = Hamster.hash( :name => "Simon", :gender => :male, #...

    1000 other key-value pairs ) person[:name] # => "Simon" friend = person.put(:name, "James") # => {:name => "James", :gender => :male, #...} Does friend have to copy everything from person?
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    NO!

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    “Efficient, immutable, and thread-safe collection classes for Ruby.” NO!

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    “Persistent, immutable, and thread-safe collection classes for Ruby.” NO!

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    zs = xs + ys

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    None
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    adding e

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    “Efficient, immutable, and thread-safe collection classes for Ruby.”

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    immutability => thread safety

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    warning: references immutable but contents might be mutable

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    require 'hamster' v = "A" h = Hamster.hash(:k=>v) #=>{:k =>

    "A"} v[0] = "B" h #=> {:k => "B"}
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    “Efficient, immutable, and thread-safe collection classes for Ruby.”

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    references https://deveo.com/blog/2013/03/22/immutability-in-ruby-part-1/ https://deveo.com/blog/2013/03/28/immutability-in-ruby-part-2/ http://clojure.org/state http://en.wikipedia.org/wiki/Persistent_data_structure https://github.com/hamstergem/hamster slides https://github.com/ryantm/lvrug_hamster