_.rb

# The beginner is given this piece of code to wrangle

def foo1
  lambda do |x|
    lambda do |y|
      lambda do |f|
        f.call(x, y)
      end
    end
  end
end

# Piece of cake: pass x, pass y, pass f

foo().call(5).call(6).call(lambda do |x,y|; x + y; end)
#=> 11

# Now the beginner is given this:

def foo2
  lambda do |x|
    lambda do |y|
      yield(x, y)
    end
  end
end

# Piece of cake, pass x, then y, then block

foo().call(5).call(6) do |x,y|
  x + y
end
#=> #<Proc:0x007f10ffccea18@(irb):160 (lambda)>

# Huh? But everyone says blocks are like functions. What happened?

# *Research*


foo2 do |baz,quux|
  baz + quux
end.call(5).call(6)
#=> 11

# Tada!
# The *key* distinction in this case: blocks must be passed *upfront* to methods