ScotRuby - Dark side of ruby

The Dark Side of Ruby
@gautamrege!
@joshsoftware

What’s the talk about?
• Ruby is AWESOME but …

• Nothing scary

• Nothing scary really

• Nothing scary
• Weirdness and Gotcha’s
really

• Nothing scary
• Weirdness and Gotcha’s
Ah-ha! Moments
really

(In)Famous Inﬁnityhttp://www.ﬂickr.com/photos/emdot/482622478/sizes/l/

(In)Famous Inﬁnity
$ irb> 1/0

$ irb> 1/0
=> ZeroDivisionError: divided by 0

$ irb> 1/0
$ irb> 1.0/0

$ irb> 1/0
$ irb> 1.0/0
=> Infinity

$ irb> 1/0
$ irb> 1.0/0
$ irb> Infinity
=> Infinity

$ irb> 1/0
$ irb> 1.0/0
$ irb> Infinity
=> Infinity
=> NameError: uninitialized constant
Infinity

#if !defined(INFINITY) || !defined(NAN)!
union bytesequence4_or_float {!
unsigned char bytesequence[4];!
float float_value;!
};!
#endif!
!
RUBY_EXTERN const union
bytesequence4_or_float rb_infinity;

#if !defined(INFINITY) || !defined(NAN)!
union bytesequence4_or_float {!
unsigned char bytesequence[4];!
float float_value;!
};!
#endif!
!
RUBY_EXTERN const union
bytesequence4_or_float rb_infinity;
include/ruby/missing.h

Base Jumping
http://www.ﬂickr.com/photos/shahdi/8035647153/sizes/l/

Base Conversions
$ irb> 12345.to_s(8)

Base Conversions
$ irb> 12345.to_s(8)
=> "30071" # => Octal

Base Conversions
$ irb> 12345.to_s(8)
$ irb> 12345.to_s(36)
=> "30071" # => Octal

Base Conversions
$ irb> 12345.to_s(8)
$ irb> 12345.to_s(36)
=> "30071" # => Octal
=> "9ix" # That is an actual number

Base Conversions
$ irb> 12345.to_s(8)
$ irb> 12345.to_s(36)
$ irb> 1234.to_s(64)
=> "30071" # => Octal

Base Conversions
$ irb> 12345.to_s(8)
$ irb> 12345.to_s(36)
$ irb> 1234.to_s(64)
=> "30071" # => Octal
=> ArgumentError: invalid radix 64

Splat Expander
Job = Struct.new(:name, :occupation)
tom = Job.new("Tom", "Developer")
name, occupation = *tom

Splat Expander
tom = Job.new("Tom", "Developer")
=> ["Tom", "Developer"]
=> name # "Tom"
=> occupation # "Developer"

Splat Expander
tom = Job.new(occupation: "Developer",
name: "Tom")

Splat Expander
tom = Job.new(occupation: "Developer",
name: "Tom")
=> name # {:occupation=>"Developer", :name=>
"Tom"}
=> occupation # nil

Hashes and Arrays
a=[1,2,3,4,5,6]!
h=Hash[*a]

Hashes and Arrays
a=[1,2,3,4,5,6]!
h=Hash[*a]
=> {1=>2, 3=>4, 5=>6}

Hashes and Arrays
a=[1,2,3,4,5,6]!
h=Hash[*a]
=> {1=>2, 3=>4, 5=>6}
[1,2,3] * 3

Hashes and Arrays
a=[1,2,3,4,5,6]!
h=Hash[*a]
=> {1=>2, 3=>4, 5=>6}
[1,2,3] * 3
=> [1,2,3,1,2,3,1,2,3]

Hashes and Arrays
a=[1,2,3,4,5,6]!
h=Hash[*a]
=> {1=>2, 3=>4, 5=>6}
[1,2,3] * 3
=> [1,2,3,1,2,3,1,2,3]
[1,2,3] * "%"

Hashes and Arrays
a=[1,2,3,4,5,6]!
h=Hash[*a]
=> {1=>2, 3=>4, 5=>6}
[1,2,3] * 3
=> [1,2,3,1,2,3,1,2,3]
[1,2,3] * "%"
=> "1%2%3"

Calling out to Stabby
blk = ->(f, *m, sl, l) do
puts sl
end

puts sl
end
blk.call(1, 2, 3, 4, 5, 6)

puts sl
end
blk.call(1, 2, 3, 4, 5, 6)
=> 5

blk.(1, 2, 3, 4, 5, 6)
puts sl
end
blk.call(1, 2, 3, 4, 5, 6)
=> 5

blk.(1, 2, 3, 4, 5, 6)
=> 5
syntax sugar for call
blk[1,2,3,4,5,6]
puts sl
end
blk.call(1, 2, 3, 4, 5, 6)
=> 5

Syntax
def foo(a=1, b=1,opts={})
end

Syntax
def foo(a: 1, b: 2)
end
keyword arguments

Syntax
def foo(a: 1, b:, c: 2)
end
def foo(a: 1, b: 2)
end
keyword arguments

Syntax
def foo(a: 1, b:, c: 2)
end
foo(a: 2)
=> ArgumentError: missing keyword: b
Mandatory keyword
arguments
def foo(a: 1, b: 2)
end
keyword arguments

The Case Statement
def multiple_of(factor)!
Proc.new {|p| p.modulo(factor).zero?}!
end!
!
number = 9!
case number!
when multiple_of(3)!
puts "Multiple of 3"!
when multiple_of(7)!
puts "Multiple of 7"!
end

Behind every case is a ===
number = 9!
case number !
when multiple_of(3)
Proc.new {|p| p.modulo(3).zero?} === 9

number = 9!
case number !
when multiple_of(3)
Proc#=== is an alias to Proc#call.

number = 9!
case number !
when multiple_of(3)
Proc.new { |p| !
p.modulo(3).zero?!
}.call(9)
Proc#=== is an alias to Proc#call.

Override the === method
to customise case
evaluation.

==, ===, eql?, equal?
http://www.ﬂickr.com/photos/gak/2418146934/sizes/o/

==, ===, eql?, equal?
irb> 1 == 1.0

==, ===, eql?, equal?
irb> 1 == 1.0
=> true # generic equality

==, ===, eql?, equal?
irb> 1 == 1.0
irb> 1 === 1.0

==, ===, eql?, equal?
irb> 1 == 1.0
irb> 1 === 1.0
=> true # case equality

==, ===, eql?, equal?
irb> 1 == 1.0
irb> 1 === 1.0
irb> 1.eql? 1.0

==, ===, eql?, equal?
=> false # equality by value
irb> 1 == 1.0
irb> 1 === 1.0
irb> 1.eql? 1.0

==, ===, eql?, equal?
irb> 1 == 1.0
irb> 1 === 1.0
irb> 1.eql? 1.0
irb> 1.equal? 1.0

==, ===, eql?, equal?
irb> 1 == 1.0
irb> 1 === 1.0
irb> 1.eql? 1.0
irb> 1.equal? 1.0
=> false # object identity

==, ===, eql?, equal?
irb> 1 == 1.0
irb> 1 === 1.0
irb> 1.eql? 1.0
irb> 1.equal? 1.0
irb> 'a'.equal? 'a'

==, ===, eql?, equal?
=> false # gotcha?
irb> 1 == 1.0
irb> 1 === 1.0
irb> 1.eql? 1.0
irb> 1.equal? 1.0
irb> 'a'.equal? 'a'

==, ===, eql?, equal?
=> false # gotcha?
irb> 1 == 1.0
irb> 1 === 1.0
irb> 1.eql? 1.0
irb> 1.equal? 1.0
irb> 'a'.equal? 'a'
irb> 1.equal? 1

==, ===, eql?, equal?
=> false # gotcha?
irb> 1 == 1.0
irb> 1 === 1.0
irb> 1.eql? 1.0
irb> 1.equal? 1.0
irb> 'a'.equal? 'a'
=> true # gotcha?
irb> 1.equal? 1

Object Ids & Fixnum
Fixnum * 2 + 1
irb> 23 * 2 + 1
=> 47
irb > 23.object_id
=> 47

Object Ids & Fixnum
Fixnum * 2 + 1
irb> 23 * 2 + 1
=> 47
irb > 23.object_id
=> 47
irb> (2**62 - 1).class
=> Fixnum
irb> (2**62).class
=> Bignum

http://www.ﬂickr.com/photos/miscdebris/6748016253/sizes/o/

3 Pulls for the Jackpot
jackpot = lambda { |x, y, z|
(x == y) == (x == z)
}
# 3 pulls
pull = jackpot.curry[rand(5)]
2.times { pull = pull.curry[rand(5)] }
!
p pull ? "Jackpot" : "Sucker!"

The curry recipe
• Return lambda till all parameters are passed.
• Evaluate the block if all parameters are passed.
pull = jackpot.curry[rand(5)]
=> #<Proc:0x007f9eec0990b0 (lambda)>
2.times { pull = pull.curry[rand(5)] }
=> true # or false

So! So you think you can tell…
Heaven from Hell
- Pink Floyd

So! So you think you can tell…
Protected from Private

Private methods
class Soldier
private
def ryan
puts "inside private ryan"
end
end
class Movie < Soldier
def name
ryan
end
end

Private methods
class Soldier
private
def ryan
puts "inside private ryan"
end
end
class Movie < Soldier
def name
ryan
end
end
Private Methods are
inherited!

class Base!
include Mongoid::Document!
end
The elusive include

Private method!
Instance method !
Deﬁned the class Module
class Base!
include Mongoid::Document!
end
The elusive include

Protected methods
• Work with objects not classes.

Protected methods
• Invoke a protected method on
another object in the same lineage

Protected methods
• Invoke a protected method on
another object in the same lineage
What the …

class Autobot
def initialize(nick); @nick = nick; end
!
protected
attr_accessor :nick
end
!
prime = Autobot.new("Optimus Prime")
p prime.nick

class Autobot
def initialize(nick); @nick = nick; end
!
protected
attr_accessor :nick
end
!
prime = Autobot.new("Optimus Prime")
p prime.nick
protected method `nick' called for
#<Autobot:0x007f92ba082330 @nick="Optimus
Prime"> (NoMethodError)

class Autobot
def fights(target)
p "I am #{self.nick}"
p "Kicking #{target.nick}'s ass"
end
protected
attr_accessor :nick
end
!
optimus = Autobot.new("Optimus Prime")
megatron = Autobot.new('Megatron')
!
optimus.fights megatron

class Autobot
def fights(target)
p "I am #{self.nick}"
p "Kicking #{target.nick}'s ass"
end
protected
attr_accessor :nick
end
!
optimus = Autobot.new("Optimus Prime")
megatron = Autobot.new('Megatron')
!
optimus.fights megatron
"I am Optimus Prime"
"Kicking Megatron's ass"

Keywords - hmm…
class Serious
def true
false
end
def false
true
end
end
die = Serious.new
p "seriously!" if die.false

Keywords - hmm…
class Serious
def true
false
end
def false
true
end
end
die = Serious.new
p "seriously!" if die.false
stack too deep?

superlative
class Search!
def search!
p "Default Search algorithm"!
end!
end!
class KeywordSearch < Search !
def search(keyword:)!
super!
end!
end!
KeywordSearch.new.search(keyword: "Ruby")

superlative
class Search!
def search!
end!
end!
super!
end!
end!
`search`: wrong number
of arguments (1 for 0)

superlative
class Search!
def search!
end!
end!
super()!
end!
end!

superlative
class Search!
def search!
end!
end!
super()!
end!
end!
And we thought parenthesis for
method invocation didn’t matter

Module mixins are funny
module Superman!
def fly; p "Superman: It's a bird"; end!
end!
!
module Batman!
def fly; p "Batman: Fly? Me?"; end!
end!
!
module Ironman!
def fly; p "Iroman: That's flying!"; end!
end

Module mixins are funny
class Tinyman!
include Superman!
include Batman!
include Ironman!
end!
!
Tinyman.new.fly
"Iroman: That's how you fly!"

Module Inheritance?
module Superman!
end!
!
module Batman!
end!
!
module Ironman!
def fly; super; p "Iroman: That's flying!"; end!
end

Module Inheritance?
module Superman!
end!
!
module Batman!
end!
!
module Ironman!
def fly; super; p "Iroman: That's flying!"; end!
end
"Batman: Fly? Me?”!
"Iroman: That's flying!"

Dynamic Inheritance!
class Tinyman!
include Superman!
include Batman!
include Ironman!
end

class Tinyman!
include Superman!
include Ironman!
include Batman!
end
Dynamic Inheritance!
class Tinyman!
include Superman!
include Batman!
include Ironman!
end

Cherry pick from Modules
module Megatron!
def power!
p "Megatron's super strength"!
end!
!
def evil!
p 'Evil genius'!
end!
end

class Hanuman!
include Megatron!
end
Hanuman.new.power!
# => "Megatron's super strength"!
Hanuman.new.evil !
# => "Evil genius" # Oh no!

class Hanuman!
def power!
Megatron.instance_method(:power).!
bind(self).call!
end!
end

class Hanuman!
def power!
Megatron.instance_method(:power).!
bind(self).call!
end!
end
Hanuman.new.power
# => "Megatron's super strength"
Hanuman.new.evil
# => undefined method `evil’...>

That’s all Folks!
@gautamrege
@joshsoftware

That’s all Folks!
@gautamrege
@joshsoftware
since 2007

ScotRuby - Dark side of ruby

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