lambda v proc v Proc.new

README

In 1.8  proc == lambda && proc != Proc.new
In 1.9  proc == Proc.new && proc != lambda

arity.rb

l = lambda {|a,b| a + b}
p = proc {|a,b| a + b}
pr = Proc.new {|a,b| a + b}

## 1.8
l[1,2,3]
#=> ArgumentError: wrong number of arguments (3 for 2)
p[1,2,3]
#=> ArgumentError: wrong number of arguments (3 for 2)
pr[1,2,3]
#=> 3

## 1.9
l[1,2,3]
#=> ArgumentError: wrong number of arguments (3 for 2)
p[1,2,3]
#=> 3
pr[1,2,3]
#=> 3

return.rb

def lamby
  f = lambda {return "from lambda!"}
  f.call
  return "from method!"
end

def procy
  f = proc {return "from proc!"}
  f.call
  return "from method!"
end

def proc_new
  f = Proc.new {return "from Proc.new!"}
  f.call
  return "from method!"
end

## 1.8
lamby #=> from method!
procy #=> from method!
proc_new #=> from Proc.new!

## 1.9
lamby #=> from method!
procy #=> from proc!
proc_new #=> from Proc.new!