Examples of Ruby hoisting variables

hoisting.rb

# generic hoisting
if true
  a = 1
end
a # => 1


begin
  b = 2
end
b # => 2


for whatevz in [1, 2]
  c = 3
end
c # => 3


# multi-level hoisting
if true
  if true
    if true
      d = 4
    end
  end
end
d # => 4


if false
  if false
    if false
      e = 5
    end
  end
end
e # => nil


# Ruby's multiline if statement hoists, but its inline one doesn't, inconsistent enough to seem like a bug:
if f = 'F'
  f # => "F"
end
f # => "F"

g if g = 'B' # => NameError: undefined local variable or method `g' for main:Object

# ~> NameError
# ~> undefined local variable or method `g' for main:Object
# ~>
# ~> /var/folders/7g/mbft22555w3_2nqs_h1kbglw0000gn/T/seeing_is_believing_temp_dir20150323-47469-1c0cwrl/program.rb:47:in `<main>'

Sorry to randomly pick out this gist, but was comparing differences in variable assignment behavior between Javascript and Ruby and stumbled upon this. I have seen it named hoisting in a few different places. That seems like a bit of a misnomer but I might just be misunderstanding. I mean, it is not hoisting the variable assignment anywhere is it? If any of those variables were called prior to the assignment with the conditionals, they would be unassigned. However, in javascript, you could call those variables prior to the conditional and they would be actually moved up and available there. Clearly Ruby has a thing they are doing here, but I guess I'm thinking that maybe hoisting is not the exact name for it. No?

I have to agree with @baldwindavid.

i total agree with you @baldwindavid

Yeah, this is different than JavaScript hoisting (confusing nonetheless).

Also, let me increase confusion by a little bit :)

g if g = 'B' # => NameError: undefined local variable or method `g' for main:Object
g # => "B"

# or, in a .rb file rather than irb/pry
begin
  g if g = 'B'
rescue => e
  p g # => "B"
  raise e
end