Crystal Clean - Speaker Deck

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CRYSTAL by Luís Zamith

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Efficient, Ruby like language FEATURES

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Static checks FEATURES

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Macros FEATURES

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Simple C bindings FEATURES

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WARNING! Pre-Alpha

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def fib(n)! if n < 3! 1! else! fib(n-1) + fib(n-2)! end! end! ! fib(35)

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RUBY def fib(n)! if n < 3! 1! else! fib(n-1) + fib(n-2)! end! end! ! fib(35)

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CRYSTAL def fib(n)! if n < 3! 1! else! fib(n-1) + fib(n-2)! end! end! ! fib(35)

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Calculating ------------------------------------- ruby 1.000 i/100ms crystal 2.000 i/100ms ----------------------------------------------------- ruby 1.268 (± 0.0%) i/s - 13.000 crystal 26.321 (± 3.8%) i/s - 264.000 ! Comparison: crystal: 26.3 i/s ruby: 1.3 i/s - 20.75x slower

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RUBY class Email! attr_reader :subject, :date, :from! ! def initialize(subject, date: "", from: "")! @subject = subject! @date = date! @from = from! end! ! def to_s ! “Date: #{date}! From: #{from}! Subject: #{subject}”! end! end

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CRYSTAL class Email! getter :subject, :date, :from! ! def initialize(subject, options = {} of Symbol => String)! @subject = subject! @date = options.fetch(:date, "")! @from = options.fetch(:from, "")! end! ! def to_s(io: IO)! io << "Date: #{date}\n! ! ! ! ! ! ! ! From: #{from}\n! Subject: #{subject}\n\n"! end! end

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Static Checks

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RUBY def string_size(str)! puts str.length! end! ! string_size("This is a string")! string_size(nil) 16 `string_size': undefined method `length' for nil:NilClass (NoMethodError)

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CRYSTAL def string_size(str)! puts str.length! end! ! string_size("This is a string")! string_size(nil) instantiating 'string_size(Nil)' undefined method 'length' for Nil

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Special getters

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CRYSTAL class Email! getter! :subject, :date, :from! ! ...! end! ! email = Email.new("Homework this week", { date: nil, from: "Ferdous" }),! ! p email.date? # nil

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CRYSTAL class Email! getter! :subject, :date, :from! ! ...! end! ! email = Email.new("Homework this week", { date: nil, from: "Ferdous" }),! ! p email.date

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CRYSTAL class Email! getter! :subject, :date, :from! ! ...! end! ! email = Email.new("Homework this week", { date: nil, from: "Ferdous" }),! ! p email.date Nil assertion failed

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CRYSTAL class Email! getter? :subject, :date, :from! ! ...! end! ! email = Email.new("Homework this week", { date: nil, from: "Ferdous" }),! ! p email.date? # nil

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CRYSTAL class Email! getter? :subject, :date, :from! ! ...! end! ! email = Email.new("Homework this week", { date: nil, from: "Ferdous" }),! ! p email.date

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CRYSTAL class Email! getter? :subject, :date, :from! ! ...! end! ! email = Email.new("Homework this week", { date: nil, from: "Ferdous" }),! ! p email.date undefined method 'date' for Email (did you mean 'date?'?)

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Macros

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RUBY class BasicObject! def self.attr_reader(*names)! names.map(&:to_s).each do |name|! class_eval "! def #{name}! @#{name}! end! "! end! end! end

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CRYSTAL class Object! macro getter(*names)! {% for name in names %}! {% name = name.var if name.is_a?(DeclareVar) %}! ! def {{name.id}}! @{{name.id}}! end! {% end %}! end! end

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C bindings

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RUBY Not very simple to connect ! Need to write C ! Need to know Ruby’s C implementation (struct, methods, etc…)

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CRYSTAL lib C! fun atoi(str : UInt8*) : Int32! end! ! p C.atoi(“28").class # Int32

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CRYSTAL @[Link("readline")]! lib LibReadline! fun readline(prompt : UInt8*) : Pointer(UInt8)! end! ! line = LibReadline.readline("What's your name?\n")! p String.new(line) # What’s your name?! # zamith! # ”zamith"

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Generics

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RUBY class Foo! attr_reader :value! ! def initialize(value)! @value = value! end! end! ! foo = Foo.new(1)! p foo.value.abs # 1! ! foo = Foo.new('a')! p foo.value.ord # 97

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CRYSTAL class Foo! getter :value! ! def initialize(@value); end! end! ! foo = Foo.new(1)! p foo.value.abs # 1! ! foo = Foo.new(‘a’)! p foo.value.ord # undefined method 'abs' for Char

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CRYSTAL class Foo(T)! getter :value! ! def initialize(@value : T); end! end! ! foo = Foo.new(1)! p foo.value.abs # 1! ! foo = Foo.new('a')! p foo.value.ord # 97

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CRYSTAL class Array(T)! include Enumerable! include Comparable(Array)! ! def initialize(size, value : T)! ! ! . . .! end! end arr = [1, 2]! arr.first.abs! ! arr = [1, '2']! arr.first.abs # error!

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Specs

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CRYSTAL require "spec"! ! class MyString! def initialize(@string); end! ! def size! @string.size! end! end! ! describe "Repo" do! describe "size" do! it "returns the size of my string" do! MyString.new("Hello").size.should eq 5! end! end! end

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Notable Misses

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CRYSTAL Single quoted strings ! require_relative ! keyword arguments ! send method_missing ! define_method ! eval

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Interesting Things

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CRYSTAL RUBY [1,2].map &.to_s.+(“ hello”) [1,2].map do |num| ! ! num.to_s.+(" hello”)! end # [“1 hello", "2 hello"] # [“1 hello", "2 hello"]

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CRYSTAL class Hash(K, V)! ...! def self.new(comp = StandardComparator, &block : (Hash(K, V), K -> V))! new block, comp! end! ! def self.new(default_value : V, comp = StandardComparator)! new(comp) { default_value }! end! ! def self.new(comparator)! new nil, comparator! end! ...! end

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CRYSTAL class Hash(K, V)! ...! def self.new(default_value = nil : V, comp = StandardComparator)! new(comp) { default_value }! end! ...! end

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CRYSTAL class Hash(K, V)! ...! def self.new(default_value = nil : V?, comp = StandardComparator)! new(comp) { default_value }! end! ...! end