In Ruby, what are the vertical lines?

Question

1.upto(9) { |x| print x }

Why won\'t this work?

{ print x |x} }

What about y?

Answer 1

It's not an operator; it's delimiting the argument list for the block. The bars are equivalent to the parens in def foo(x). You can't write it as {print x |x} for the same reason this:

def foo(x)
  puts "It's #{x}"
end

can't be rewritten as this:

def foo
  puts "It's #{x}" (x
end