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# Excerpted from "The ThoughtWorks Anthology",
# published by The Pragmatic Bookshelf.
# Copyrights apply to this code. It may not be used to create training material, 
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#---
#global functions again eliminating all parens

item :secure_air_vent

item :acid_bath
uses acid
acid_type :hcl
acid_grade 5
uses electricity 
electricity_power 12

item :camera
uses electricity 
electricity_power 1

item :small_power_plant
provides electricity 
electricity_power 11
depends :secure_air_vent