Difference Between Ruby 1.8 and Ruby 1.9

What is the difference between Ruby 1.8 and Ruby 1.9

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Colon No Longer Valid In When Statements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!

String#[] Differences between Ruby 1.8.7 and 1.9.3

To get the old behavior, use String#getbyte, as in:

"\200\001\002\004\b\020".getbyte(0)

String length difference between ruby 1.8 and 1.9

This is a Unicode issue. The string you are using contains characters outside the ASCII range, and the UTF-8 encoding that is frequently used encodes those as 2 (or more) bytes.

Ruby 1.8 did not handle Unicode properly, and length simply gives the number of bytes in the string, which results in fun stuff like:

"ą".length
=> 2

Ruby 1.9 has better Unicode handling. This includes length returning the actual number of characters in the string, as long as Ruby knows the encoding:

"ä".length
=> 1

One possible workaround in Ruby 1.8 is using regular expressions, which can be made Unicode aware:

"ą".scan(/./mu).size
=> 1

Ruby 1.8.7 versus Ruby 1.9+ performance

These could help you

http://nerds.airbnb.com/upgrading-from-ree-187-to-ruby-193

http://blog.pothoven.net/2012/10/ruby-187-vs-193-performance.html

http://pulse.sportngin.com/news_article/show/156863?referrer_id=543230

note that ruby 2 has even better performance

What is the difference between ruby 1.8.7 and 1.9.3 that causes session_store syntax errors in Rails?

The line that does not work in 1.8 is

 Xxx::Application.config.session_store :cookie_store, key: '_xxx_session'

It uses new hash notation. To make it working for 1.8 change it to

 Xxx::Application.config.session_store :cookie_store, :key => '_xxx_session'

Difference in `Array#to_s` in Ruby 1.8 and Ruby 1.9

Here's what is actually in Ruby source code:

1.8.7:

rb_ary_to_s(ary)
    VALUE ary;
{
    if (RARRAY(ary)->len == 0) return rb_str_new(0, 0);
    return rb_ary_join(ary, rb_output_fs);
}

In other words, in 1.8.7, to_s calls join.

1.9.3:

rb_ary_inspect(VALUE ary)
{
    if (RARRAY_LEN(ary) == 0) return rb_usascii_str_new2("[]");
    return rb_exec_recursive(inspect_ary, ary, 0);
}

VALUE
rb_ary_to_s(VALUE ary)
{
    return rb_ary_inspect(ary);
}

In other words, in 1.9.3, to_s delegates to inspect.

Note: in future, if you're wondering about a difference you're observing between two versions, you can try taking a look at source code. Easy to pull down from here: https://github.com/ruby/ruby

Not everything is going to be easy to find in there of course, but if you search around for a bit you can often find good leads. In this case, array.c has what you're looking for.

Then you can switch back and forth between versions by issuing git checkout ruby_1_8_7 and git checkout ruby_1_9_3.

Differences in date string parsing between Ruby 1.9.3 and Ruby 1.8.7

Would it be an option for you to use Time.strptime("01/28/2012", "%m/%d/%Y") in place of Time.parse? That way you have better control over how Ruby is going to parse the date.

If not there are gems: (e.g. ruby-american_date) to make the Ruby 1.9 Time.parse behave like Ruby 1.8.7, but only use it if it's absolutely necessary.

1.9.3-p0 :002 > Time.parse '01/28/2012'
ArgumentError: argument out of range

1.9.3-p0 :003 > require 'american_date'
1.9.3-p0 :004 > Time.parse '01/28/2012'
 => 2012-01-28 00:00:00 +0000 

Why does this code work in ruby 1.8 and not ruby 1.9?

It's to avoid ambiguity. Consider the following:

def foo(a, b = 1) # foo takes an optional second argument
end

[foo 1, 2]

This could be interpreted as [(foo 1), 2] or as [(foo 1, 2)].

There are two references in the Calling Methods docs (although not directly related to the array literal):

Note that the parenthesis are optional ... Except when there is difference between using and omitting parentheses

In many cases parenthesis are not necessary when sending a message ... However, parenthesis are necessary to avoid ambiguity.

Different behavior of methods.include? between ruby 1.8.7 and ruby 1.9 & 2

By checking the difference between ruby 1.8 and 1.9 (and later), I found the reason is:

'instance_methods' has been changed from array of strings to array of symbols

A proper way of checking 'whether the method is defined' is:

x.respond_to?(:hello) # or string, both work

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