From: Aaron Patterson <aaron@...>
Date: 2011-03-02T04:22:38+09:00
Subject: [ruby-core:35403] Why are hash keys sometimes duped?


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Why are some objects duped when they are used as hash keys and other
objects are not?

    irb(main):001:0> list =3D %w{ hello }
    =3D> ["hello"]
    irb(main):002:0> str =3D "world"
    =3D> "world"
    irb(main):003:0> map =3D { list =3D> 1, str =3D> 2 }
    =3D> {["hello"]=3D>1, "world"=3D>2}
    irb(main):005:0> list << "world"
    =3D> ["hello", "world"]
    irb(main):006:0> map
    =3D> {["hello", "world"]=3D>1, "world"=3D>2}
    irb(main):007:0> str.replace("hi!")
    =3D> "hi!"
    irb(main):008:0> str
    =3D> "hi!"
    irb(main):009:0> map
    =3D> {["hello", "world"]=3D>1, "world"=3D>2}
    irb(main):010:0> RUBY_VERSION
    =3D> "1.9.3"
    irb(main):011:0>

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Aaron Patterson
http://tenderlovemaking.com/

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