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

In the piece of code you have specified, vertical lines are a part of the block definition syntax. So { |x| print x } is a block of code provided as a parameter to the upto method, 9 is also a parameter passed to the upto method.

Block of code is represented by a lambda or an object of class Proc in Ruby. lambda in this case is an anonymous function.

So just to draw an analogy to the function definition syntax,

def function_name(foo, bar, baz)
  # Do something
end


{       # def function_name (Does not need a name, since its anonymous)
|x|     #   (foo, bar, baz)
print x #   # Do Something
}       # end