What is the difference between Ruby 1.8 and Ruby 1.9

Ruby Problem Overview

I'm not clear on the differences between the "current" version of Ruby (1.8) and the "new" version (1.9). Is there an "easy" or a "simple" explanation of the differences and why it is so different?

Ruby Solutions

Solution 1 - Ruby

Sam Ruby has a cool slideshow that outline the differences.

In the interest of bringing this information inline for easier reference, and in case the link goes dead in the abstract future, here's an overview of Sam's slides. The slideshow is less overwhelming to review, but having it all laid out in a list like this is also helpful.

Ruby 1.9 - Major Features

Performance
Threads/Fibers
Encoding/Unicode
gems is (mostly) built-in now
if statements do not introduce scope in Ruby.

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Colon No Longer Valid In When Statements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

(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

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

HTH!

Solution 2 - Ruby

One huge difference would be the move from Matz's interpreter to YARV, a bytecode virtual machine that helps significantly with performance.

Solution 3 - Ruby

Many now recommend The Ruby Programming Language over the Pickaxe - more to the point, it has all the details of the 1.8/1.9 differences.

Solution 4 - Ruby

Some more changes:

Returning a splat singleton array:

def function
  return *[1]
end

a=function

ruby 1.9 : [1]
ruby 1.8 : 1

array arguments

def function(array)
  array.each { |v| p v }
end
function "1"

ruby 1.8: "1"
ruby 1.9: undefined method `each' for "1":String

Content Type	Original Author	Original Content on Stackoverflow
Question	salt.racer	View Question on Stackoverflow
Solution 1 - Ruby	Tim Sullivan	View Answer on Stackoverflow
Solution 2 - Ruby	Sören Kuklau	View Answer on Stackoverflow
Solution 3 - Ruby	Dave Everitt	View Answer on Stackoverflow
Solution 4 - Ruby	Wim Yedema	View Answer on Stackoverflow

Ruby Problem Overview

Ruby Solutions

Solution 1 - Ruby

Ruby 1.9 - Major Features

What's changed?

Single character strings.

String index.

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

Array.to_s Now Contains Punctuation

Colon No Longer Valid In When Statements

Block Variables Now Shadow Local Variables

Hash.index Deprecated

Fixnum.to_sym Now Gone

Hash Keys Now Unordered

Stricter Unicode Regular Expressions

tr and Regexp Now Understand Unicode

pack and unpack

BasicObject More Brutal Than BlankSlate

Delegation Changes

Use of $KCODE Produces Warnings

instance_methods Now an Array of Symbols

Source File Encoding

Basic

Emacs

Shebang

Real Threading

What's New?

Alternate Syntax for Symbol as Hash Keys

Block Local Variables

Inject Methods

to_enum

No block? Enum!

Lambda Shorthand

Complex Numbers

Decimal Is Still Not The Default

Regex “Properties”

Splat in Middle

Fibers

Break Values

“Nested” Methods

Solution 2 - Ruby

Solution 3 - Ruby

Solution 4 - Ruby

How can I evaluate C# code dynamically?

How can I measure the similarity between two images?

Attributions

`Array.to_s` Now Contains Punctuation

`Hash.index` Deprecated

`Fixnum.to_sym` Now Gone

`tr` and `Regexp` Now Understand Unicode

`pack` and `unpack`

`BasicObject` More Brutal Than `BlankSlate`

`instance_methods` Now an Array of Symbols

`to_enum`