# File lib/rake.rb, line 173
173:     def invoke
174:       if $trace
175:         puts "** Invoke #{name} #{format_trace_flags}"
176:       end
177:       return if @already_invoked
178:       @already_invoked = true
179:       @prerequisites.each { |n| Rake::Task[n].invoke }
180:       execute if needed?
181:     end