cmd/leaves: general cleanup.

Library/Homebrew/cmd/leaves.rb

@@ -10,15 +10,12 @@ module Homebrew
 
   def leaves
     installed = Formula.installed.sort
-    deps_of_installed = Set.new
 
-    installed.each do |f|
+    deps_of_installed = installed.flat_map do |f|
-      deps = f.runtime_dependencies.map { |d| d.to_formula.full_name }
+      f.runtime_dependencies.map(&:to_formula).map(&:full_name)
-      deps_of_installed.merge(deps)
     end
 
-    installed.each do |f|
+    leaves = installed.map(&:full_name) - deps_of_installed
-      puts f.full_name unless deps_of_installed.include? f.full_name
+    leaves.each(&method(:puts))
-    end
   end
 end