Ruby 1.9: What to Expect

Sam Ruby @ OSCON 2008, Portland, Oregon, July 2008¹

¹ Adapted S6 Version from Original Slide Deck

About Sam Ruby

• Agile Web Development with Rails (3rd Edition)
• Apache Software Foundation
• Atom / Feed Validator
• ECMA .NET CLI (No longer active)
• PHP Group (No longer active)
• RESTful Web Services

- intertwingly.net

Agenda

• Part 0: Overview
• Part 1: What’s Changed?
• Part 2: What’s New?

Part 0 – Overview

What is Ruby?

• MRI (Matz’ Ruby Interpreter)
• Rubinius – RubySpec
• JRuby
• IronRuby
• Ruby.NET
• MacRuby
• MagLev
• YARV (Yet Another Ruby Virtual-machine)

Ruby 1.9 – Major Features

• Performance
• Threads/Fibers
• Encoding/Unicode
• gems is (mostly) built-in now
  • No contribs

One Lesson

If you can only take away one message from this presentation:

• if statements do not introduce scope in Ruby.

Replace Methods

Bilingual Ruby

class Employee
  if String.method_defined?(:encode)
    def name
      ...
    end
  else
    def name
      ...
    end
  end
end

Replace Implementation

Bilingual Ruby

if String.method_defined?(:encode)
  module Builder
    ...
  end
else
  class String
    ...
  end
end

Continuous Integration (CI) Efforts

• Ruby
• Bacon
• Builder
• html5lib
• libxml2
• OpenID
• REXML
• Rake (contrib)
• XMPP4R

Part 1 – What’s Changed?

Single Character Strings

Ruby 1.9

irb(main):001:0> ?c
=> "c"

Ruby 1.8.6

irb(main):001:0> ?c
=> 99

String Index

Ruby 1.9

irb(main):001:0> "cat"[1]
=> "a"

Ruby 1.8.6

irb(main):001:0> "cat"[1]
=> 97

{"a","b"} No Longer Supported

Ruby 1.9

irb(main):002:0> {1,2}
SyntaxError: (irb):2: syntax error, unexpected ',', expecting tASSOC

Ruby 1.8.6

irb(main):001:0> {1,2}
=> {1=>2}

Action: Convert to {1 => 2}

Array.to_s Now Contains Punctuation

Ruby 1.9

irb(main):001:0> [1,2,3].to_s
=> "[1, 2, 3]"

Ruby 1.8.6

irb(main):001:0> [1,2,3].to_s
=> "123"

Action: Use .join instead

Colon No Longer Valid In When Statements

Ruby 1.9

irb(main):001:0> case 'a'; when /\w/: puts 'word'; end
SyntaxError: (irb):1: syntax error, unexpected ':',
expecting keyword_then or ',' or ';' or '\n'

Ruby 1.8.6

irb(main):001:0> case 'a'; when /\w/: puts 'word'; end
word

Action: Use semicolon, then, or newline

Block Variables Now Shadow Local Variables

Ruby 1.9

irb(main):001:0> i=0; [1,2,3].each {|i|}; i
=> 0
irb(main):002:0> i=0; for i in [1,2,3]; end; i
=> 3

Ruby 1.8.6

irb(main):001:0> i=0; [1,2,3].each {|i|}; i
=> 3

Hash.index Deprecated

Ruby 1.9

irb(main):001:0> {1=>2}.index(2)
(irb):18: warning: Hash#index is deprecated; use Hash#key
=> 1
irb(main):002:0> {1=>2}.key(2)
=> 1

Ruby 1.8.6

irb(main):001:0> {1=>2}.index(2)
=> 1

Action: Use Hash.key

Fixnum.to_sym Now Gone

Ruby 1.9

irb(main):001:0> 5.to_sym
NoMethodError: undefined method 'to_sym' for 5:Fixnum

Ruby 1.8.6

irb(main):001:0> 5.to_sym
=> nil

Fixnum.to_sym Now Gone (Cont’d)

Ruby 1.9

# Find an argument value by name or index.
def [](index)
  lookup(index.to_sym)
end

svn.ruby-lang.org/repos/ruby/trunk/lib/rake.rb

Hash Keys Now Unordered

Ruby 1.9

irb(main):001:0> {:a=>"a", :c=>"c", :b=>"b"}
=> {:a=>"a", :c=>"c", :b=>"b"}

Ruby 1.8.6

irb(main):001:0> {:a=>"a", :c=>"c", :b=>"b"}
=> {:a=>"a", :b=>"b", :c=>"c"}

Order is insertion order

Stricter Unicode Regular Expressions

Ruby 1.9

irb(main):001:0> /\x80/u
SyntaxError: (irb):2: invalid multibyte escape: /\x80/

Ruby 1.8.6

irb(main):001:0> /\x80/u
=> /\x80/u

tr and Regexp Now Understand Unicode

Ruby 1.9

unicode(string).tr(CP1252_DIFFERENCES, UNICODE_EQUIVALENT).
  gsub(INVALID_XML_CHAR, REPLACEMENT_CHAR).
  gsub(XML_PREDEFINED) {|c| PREDEFINED[c.ord]}

pack and unpack

Ruby 1.8.6

def xchr(escape=true)
  n = XChar::CP1252[self] || self
  case n when *XChar::VALID
    XChar::PREDEFINED[n] or 
      (n>128 ? n.chr : (escape ? "&##{n};" : [n].pack('U*')))
  else
    Builder::XChar::REPLACEMENT_CHAR
  end
end
unpack('U*').map {|n| n.xchr(escape)}.join

BasicObject More Brutal Than BlankSlate

Ruby 1.9

irb(main):001:0> class C < BasicObject; def f; Math::PI; end; end; C.new.f
NameError: uninitialized constant C::Math

Ruby 1.8.6

irb(main):001:0> require 'blankslate'
=> true
irb(main):002:0> class C < BlankSlate; def f; Math::PI; end; end; C.new.f
=> 3.14159265358979

Action: Use ::Math::PI

Delegation Changes

Ruby 1.9

irb(main):002:0> class C < SimpleDelegator; end
=> nil
irb(main):003:0> C.new('').class
=> String

Ruby 1.8.6

irb(main):002:0> class C < SimpleDelegator; end
=> nil
irb(main):003:0> C.new('').class
=> C
irb(main):004:0>

Defect 17700

Use of $KCODE Produces Warnings

Ruby 1.9

irb(main):004:1> $KCODE = 'UTF8'
(irb):4: warning: variable $KCODE is no longer effective; ignored
=> "UTF8"

Ruby 1.8.6

irb(main):001:0> $KCODE = 'UTF8'
=> "UTF8"

instance_methods Now an Array of Symbols

Ruby 1.9

irb(main):001:0> {}.methods.sort.last
=> :zip

Ruby 1.8.6

irb(main):001:0> {}.methods.sort.last
=> "zip"

Action: Replace instance_methods.include? with method_defined?

Source File Encoding

Basic

# coding: utf-8

Emacs

# -*- encoding: utf-8 -*-

Shebang

#!/usr/local/rubybook/bin/ruby
# encoding: utf-8

Real Threading

• Race Conditions
• Implicit Ordering Assumptions
• Test Code

Implications

• Changes are straightforward
• Cumulative effect is massive
• The biggest obstacle to Ruby 1.9’s adoption is the sheer number of mostly working but essentially unmaintained gems that virtually everybody in the Ruby community depends on
• Emergence of alternate implementations also a source for inertia

Recommendations

Encourage maintainers of gems to:

• Produce versions of gems that work with 1.8.x and 1.9
• For long term, move to distributed version control systems (DVCS) like git

Rails Dependencies

actionmailer-2.1.0, actionpack-2.1.0, activerecord-2.1.0, activeresource-2.1.0, activesupport-2.1.0, builder-2.1.2, memcache-client-1.5.0, rails-2.1.0, rake-0.8.1, sources-0.0.1, text-format-0.6.3, tmail-1.2.3, tzinfo-0.3.8, xml-simple-1.0.11, html-scanner, db2.rb, mysql.rb

Part 2 – What’s New?

Alternate Syntax for Symbol as Hash Keys

Ruby 1.9

{a: b}

redirect_to action: show

Ruby 1.8.6

{:a => b}

redirect_to :action => show

Block Local Variables

Ruby 1.9

[1,2].each {|value; t| t=value*value}

Inject Methods

Ruby 1.9

[1,2].inject(:+)

Ruby 1.8.6

[1,2].inject {|a,b| a+b}

to_enum

Ruby 1.9

short_enum = [1, 2, 3].to_enum
long_enum = ('a'..'z').to_enum
loop do
  puts "#{short_enum.next} #{long_enum.next}"
end

No block? Enum!

Ruby 1.9

e = [1,2,3].each

Lambda Shorthand

Ruby 1.9

p = -> a,b,c {a+b+c}
puts p.(1,2,3)
puts p[1,2,3]

Ruby 1.8.6

p = lambda {|a,b,c| a+b+c}
puts p.call(1,2,3)

Complex Numbers

Ruby 1.9

Complex(3,4) == 3 + 4.im

Decimal Is Still Not The Default

Ruby 1.9

irb(main):001:0> 1.2-1.1
=> 0.0999999999999999

Regex “Properties”

Ruby 1.9

/\p{Space}/

Ruby 1.8.6

/[:space:]/

Splat in Middle

Ruby 1.9

def foo(first, *middle, last)

(->a, *b, c {p a-c}).(*5.downto(1))

Fibers

Ruby 1.9

f = Fiber.new do
  a,b = 0,1
  Fiber.yield a
  Fiber.yield b
  loop do
    a,b = b,a+b
    Fiber.yield b
  end
end
10.times {puts f.resume}

Break Values

Ruby 1.9

match =
   while line = gets
     next if line =~ /^#/
     break line if line.find('ruby')
   end

“Nested” Methods

Ruby 1.9

def toggle
  def toggle
    "subsequent times"
  end
  "first time"
end

Questions

• Any questions?
• Programming Ruby 3
• Thanks for coming!