# File lib/rake.rb, line 163
163:   def invoke
164:     if $trace
165:       puts "** Invoke #{name} #{format_trace_flags}"
166:     end
167:     return if @already_invoked
168:     @already_invoked = true
169:     @prerequisites.each { |n| Task[n].invoke }
170:     execute if needed?
171:   end