fairchild · April 15, 2012 16:52
diff --git a/update_existing_hash.rb b/update_existing_hash.rb

 # merge a hash, only updating the first hash with values from the second where the first already has an exisitng key
 # for example, 
 # a= {"a"=>1, "b"=>2, "z"=>3}
 # b= {"x"=>99, "y"=>88, "z"=>77}
 # will result in {"a"=>1, "b"=>2, "z"=>77}
 def update_existing(a, b)
  a.inject({}){|sum, el|  (b.has_key?(el.first) && b[el.first]) ?  sum.update(el.first=>b[el.first]) : sum[el.first]=a[el.first]; sum}
 end

	# merge a hash, only updating the first hash with values from the second where the first already has an exisitng key
	# for example,
	# a= {"a"=>1, "b"=>2, "z"=>3}
	# b= {"x"=>99, "y"=>88, "z"=>77}
	# will result in {"a"=>1, "b"=>2, "z"=>77}
	def update_existing(a, b)
	a.inject({}){\|sum, el\| (b.has_key?(el.first) && b[el.first]) ? sum.update(el.first=>b[el.first]) : sum[el.first]=a[el.first]; sum}
	end
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