Code Golf!

lib/pry/hooks.rb

@@ -37,18 +37,17 @@ class Pry
     end
 
     def merge_arrays(array1, array2)
-      keys = array1.map {|(k,v)| k}
-      hash = {}
-      array1.each{|(k,v)| hash[k]=v}
-      keys.push(*array2.map {|(k,v)| k})
-      array2.each{|(k,v)| hash[k]=v}
-      result = []
-      keys.uniq!
-      keys.each{|k| result.push([k,hash[k]]) }
-      result
+      uniq_keeping_last(array1 + array2, &:first)
     end
     private :merge_arrays
 
+    def uniq_keeping_last(input, &block)
+      hash, output = {}, []
+      input.reverse.each{ |i| hash[block[i]] ||= (output.unshift i) }
+      output
+    end
+    private :uniq_keeping_last
+
     # Return a new `Pry::Hooks` instance containing a merge of the contents of two `Pry:Hooks` instances,
     # @param [Pry::Hooks] other The `Pry::Hooks` instance to merge
     # @return [Pry::Hooks] The new hash.