From: Albert Schlef <albertschlef@...>
Date: 2011-03-23T20:59:37+09:00
Subject: Re: A question about Ruby 1.9's "external encoding"

Robert K. wrote in post #988839:
> What *I* find slightly puzzling is this:
>
> irb(main):001:0> s1 = "a"
> => "a"
> irb(main):002:0> s1.encoding
> => #<Encoding:UTF-8>
> irb(main):003:0> s2 = s1.encode 'ISO-8859-1'
> => "a"
> irb(main):004:0> s2.encoding
> => #<Encoding:ISO-8859-1>
> irb(main):005:0> s1 == s2
> => true
> irb(main):006:0> s1.eql? s2
> => true
> irb(main):007:0> [s1.hash, s2.hash]
> => [1003075638, 1003075638]
> irb(main):008:0> [s1.hash, s2.hash].uniq
> => [1003075638]
> irb(main):009:0> s1.encoding == s2.encoding
> => false
>
> Apparently only the byte representation is used for equivalence checks
> and the encoding is ignored.

I don't think this is true:

irb(main):043:0> utf = "\u05D0"  # Alef
=> "א"
irb(main):044:0> latin = utf.dup; latin.force_encoding 'ISO-8859-1'
=> "�\x90"
irb(main):045:0> [utf.bytes.to_a, latin.bytes.to_a]  # They have the
same bytes
=> [[215, 144], [215, 144]]
irb(main):048:0> [utf.valid_encoding?, latin.valid_encoding?] # And are 
ok
=> [true, true]
irb(main):046:0> utf == latin   # But they aren't equal
=> false

In your case it's good the strings are considered equal: we want to know
if the letters are all the same. "a" is "a"... no matter what encoding.

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