Summary: 
 I'm not guessing how to examine a method (or property ?), given its
name. Details below, in case I'm going far astray.

The sample code on page

  http://httpd.chello.nl/k.vangelder/ruby/learntk/combining.html

specifically this line

  image = TkPhotoImage.new() { file "background.gif"; height 50 }

is yielding me an error in number of arguments to height:

>ruby stuff.rb
stuff.rb:14:in `height': wrong number of arguments(1 for 0)
(ArgumentError)
	from stuff.rb:14
	from stuff.rb:14:in `new'
	from stuff.rb:14:in `new'
	from stuff.rb:14

I think it would be good if I understood how to figure out the correct
number of
arguments to height using Ruby, but apparently I'm not clever enough
yet for this.

I have found that the class TkPhotoImage is a first class object, and
has some methods

  TkPhotoImage.public_instance_methods

but none of them are "height". So I tried to walk up the hierarchy
with a lucky guess

  TkPhotoImage.superclass

TkImage

  TkImage.public_instance_methods

Here I find "height". But now I am not clever enough for the next step
(and I bet there is some simple next step, to see info about this
method/property)

  TkImage.instance_method("height")

#<UnboundMethod: TkImage#height>

I wonder if someone could give me a suggestion or pointer about how I
should find out more info about the "height" property or method of the
class "TkImage" (preferably  using Ruby, if that is reasonably easy).

Thanks for any ideas.