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Contents
#--
# Credit goes to Tilo Sloboda.
#++
class Hash
# Create a "true" inverse hash by storing mutliple values
# in Arrays.
#
# h = {"a"=>3, "b"=>3, "c"=>3, "d"=>2, "e"=>9, "f"=>3, "g"=>9}
#
# h.invert #=> {2=>"d", 3=>"f", 9=>"g"}
# h.inverse #=> {2=>"d", 3=>["f", "c", "b", "a"], 9=>["g", "e"]}
# h.inverse.inverse #=> {"a"=>3, "b"=>3, "c"=>3, "d"=>2, "e"=>9, "f"=>3, "g"=>9}
# h.inverse.inverse == h #=> true
#
def inverse
i = Hash.new
self.each_pair{ |k,v|
if (Array === v)
v.each{ |x| i[x] = ( i.has_key?(x) ? [k,i[x]].flatten : k ) }
else
i[v] = ( i.has_key?(v) ? [k,i[v]].flatten : k )
end
}
return i
end
end
# _____ _
# |_ _|__ ___| |_
# | |/ _ \/ __| __|
# | | __/\__ \ |_
# |_|\___||___/\__|
#
=begin test
require 'test/unit'
class TCHash < Test::Unit::TestCase
def test_each_with_key
h1 = { :a=>1, :b=>2, :c=>2 }
h2 = h1.inverse
assert_equal( {1=>:a, 2=>[:b,:c]}, h2 )
end
end
=end
Version data entries
5 entries across 5 versions & 1 rubygems