#---
# Excerpted from "The ThoughtWorks Anthology",
# published by The Pragmatic Bookshelf.
# Copyrights apply to this code. It may not be used to create training material, 
# courses, books, articles, and the like. Contact us if you are in doubt.
# We make no guarantees that this code is fit for any purpose. 
# Visit http://www.pragmaticprogrammer.com/titles/twa for more book information.
#---
#global functions again, but using parse state

item(:secure_air_vent)

item(:acid_bath)
uses(acid)
acid_type(:hcl)
acid_grade(5)
uses(electricity(12))

item(:camera)
uses(electricity(1))

item(:small_power_plant)
provides(electricity(11))
depends(:secure_air_vent)