Why do Ruby procs/blocks with splat arguments behave differently than methods and lambdas? -

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why ruby (2.0) procs/blocks splat arguments behave differently methods , lambdas?

def foo (ids, *args)   p ids end foo([1,2,3]) # => [1, 2, 3]  bar = lambda |ids, *args|   p ids end bar.call([1,2,3]) # => [1, 2, 3]  baz = proc |ids, *args|   p ids end baz.call([1,2,3]) # => 1  def qux (ids, *args)   yield ids, *args end qux([1,2,3]) { |ids, *args| p ids } # => 1

here's confirmation of behavior, without explanation: http://makandracards.com/makandra/20641-careful-when-calling-a-ruby-block-with-an-array

there 2 types of proc objects: lambda handles argument list in same way normal method, , proc use "tricks" (proc#lambda?). proc splat array if it's argument, ignore arguments, assign nil missing ones. can partially mimic proc behavior lambda using destructuring:

->((x, y)) { [x, y] }[1]         #=> [1, nil] ->((x, y)) { [x, y] }[[1, 2]]    #=> [1, 2] ->((x, y)) { [x, y] }[[1, 2, 3]] #=> [1, 2] ->((x, y)) { [x, y] }[1, 2]      #=> argumenterror

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