Question

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?

Answer 1

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Colon No Longer Valid In When Statements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!