Unicode in Regex

[Greg Willits]

This is mostly a Ruby thing, and partly a Rails thing.

I'm expecting a validate_format_of with a regex like this

/^[a-zA-Z\xC0-\xD6\xD9-\xF6\xF9-\xFF\.\'\-\ ]*?$/

to allow many of the normal characters like ö é å to be submitted via
web form.

However, the extended characters are being rejected.

This works just fine though (which is just a-zA-Z)

/^[\x41-\x5A\x61-\x7A\.\'\-\ ]*?$/

It also seems to fail with full \x0000 numbers, is there limit at \xFF?

Some plain Ruby tests seem to suggest unicode characters don't work at
all??

p 'abvHgtwHFuG'.scan(/[a-z]/)
p 'abvHgtwHFuG'.scan(/[A-Z]/)
p 'abvHgtwHFuG'.scan(/[\x41-\x5A]/)
p 'abvHgtwHFuG'.scan(/[\x61-\x7A]/)
p 'aébvHögtåwHÅFuG'.scan(/[\xC0-\xD6\xD9-\xF6\xF9-\xFF]/)

["a", "b", "v", "g", "t", "w", "u"]
["H", "H", "F", "G"]
["H", "H", "F", "G"]
["a", "b", "v", "g", "t", "w", "u"]
["\303", "\303", "\303", "\303"]

So, what's the secret to using unicode character ranges in Ruby regex
(or Rails validations)?

--
def gw
acts_as_n00b
writes_at(www.railsdev.ws)
end
--
Posted via http://www.ruby-forum.com/.

[Dale Martenson]

On Nov 30, 2:18 pm, Greg Willits <li...@gregwillits.ws> wrote:

> So, what's the secret to using unicode character ranges in Ruby regex
> (or Rails validations)?

Tim Bray gave a great talk about I18N, M17N and Unicode at the 2006
Ruby Conference. His presentation can be found at:

http://www.tbray.org/talks/rubyconf2006.pdf

He described how many member functions have trouble dealing with these
character sets. He made special reference to regular expressions.

--Dale

[Greg Willits]

That's just beyond sad.

I've been using Lasso for several years now, and *2003* it provided
complete support for Unicode. I know there's some esoterics it may not
deal with, but for all practical purposes we can round-trip data in
western and eastern languages with Lasso quite easily.

How can all these other languages be so far behind?

Pretty bad if I can't even allow Mr. Muños or Göran to enter their names
in a web form with proper server side validations. Aargh.

-- gw

[MonkeeSage]

Ruby 1.8 doesn't have unicode support (1.9 is starting to get it).
Everything in ruby is a bytestring.

irb(main):001:0> 'aébvHögtåwHÅFuG'.scan(/./)
=> ["a", "\303", "\251", "b", "v", "H", "\303", "\266", "g", "t",
"\303", "\245", "w", "H", "\303", "\205", "F", "u", "G"]

So your character class is matching the first byte of the composite
characters (which is \303 in octal), and skipping the next (since it's
below the range). You probably want something like...

reg = /[\xc0-\xd6\xd9-\xf6\xf9-\xff][\x80-\xbc]/
'aébvHögtåwHÅFuG'.scan(reg)

irb(main):006:0* reg = /[\xc0-\xd6\xd9-\xf6\xf9-\xff][\x80-\xbc]/
=> /[\xc0-\xd6\xd9-\xf6\xf9-\xff][\x80-\xbc]/
irb(main):007:0> 'aébvHögtåwHÅFuG'.scan(reg)
=> ["\303\251", "\303\266", "\303\245", "\303\205"]
irb(main):008:0> "å" == "\303\245"
=> true

Ps. I'm not entirely sure the value of the second character class is
right.

Regards,
Jordan

[Jimmy Kofler]

> Unicode in Regex
> Posted by Greg Willits (-gw-) on 30.11.2007 21:18

> This is mostly a Ruby thing, and partly a Rails thing.
>
> I'm expecting a validate_format_of with a regex like this
>
> /^[a-zA-Z\xC0-\xD6\xD9-\xF6\xF9-\xFF\.\'\-\ ]*?$/
>
> to allow many of the normal characters like ö é å to be submitted via
> web form.

How about the utf8 validation regex here:
http://snippets.dzone.com/posts/show/4527 ?

[Greg Willits]

Greg Willits wrote:

> I'm expecting a validate_format_of with a regex like this
> /^[a-zA-Z\xC0-\xD6\xD9-\xF6\xF9-\xFF\.\'\-\ ]*?$/
> to allow many of the normal characters like ö é å to be submitted via
> web form. However, the extended characters are being rejected.

So, I've been pounding the web for info on UTF8 in Ruby and Rails the
past couple days to concoct some validations that allow UTF8
characters. I have discovered that I can get a little further by doing
the
following:
- declaring $KCODE = 'UTF8'
- adding /u to regex expressions.

The only thing not working now is the ability to define a range of \x
characters in a regex.

So, this /^[a-zA-Z\xE4]*?&/u will validate that a string is allowed
to have an ä in it. Perfect.

But... this fails /^[a-zA-Z\xE4-\xE6]*?&/u

But... this works /^[a-zA-Z\xE4\xE5\xE6]*?&/u

I've boiled the experiments down to realizing I can't define a range
with \x

Is this just one of those things that just doesn't work yet WRT Ruby/
Rails/UTF8, or is there another syntax? I've scoured all the regex
docs I can find, and they seem to indicate a range should work.

For now, I just have all the characters I want included < \xFF listed
individually.

utf_accents = '\xC0\xC1\xC2\.......'

Is_person_name = /^[a-zA-Z#{utf_accents}\.\'\-\ ]*?$/u

But I'd like to solve the range notation if I can.

[Daniel DeLorme]

MonkeeSage wrote:
> Ruby 1.8 doesn't have unicode support (1.9 is starting to get it).

I enrages me to see this kind of FUD. Through regular expressions, ruby
1.8 has 80-90% complete utf8 support. And oniguruma makes utf8 support
well-near 100% complete.

>> 'aébvHögtåwHÅFuG'.scan(/./u)
=> ["a", "é", "b", "v", "H", "ö", "g", "t", "å", "w", "H", "Å", "F",
"u", "G"]

>> 'aébvHögtåwHÅFuG'.scan(/[éöåÅ]/u)
=> ["é", "ö", "å", "Å"]

Ok, sometimes you have to take a weird approach because of the missing
10-20%, but it's still workable
>> 'aébvHögtåwHÅFuG'.scan(/(?:\303\251|\303\266|\303\245|\303\205)/u)
=> ["é", "ö", "å", "Å"]

> Everything in ruby is a bytestring.

YES! And that's exactyly how it should be. Who is it that spread the
flawed idea that strings are fundamentally made of characters? I'd like
to slap him around a little. Fundamentally, ever since the word "string"
was applied to computing, strings were made of 8-BIT CHARS, not n-bit
characters. If only the creators of C has called that datatype "byte"
instead of "char" it would have saved us so many misunderstandings.

Usually the complaint about the support lack of unicode support is that
something like "日本語".length returns 9 instead of 3, or that "日本語
".index("語") returns 6 instead of 2. It's nice that people want to
completely redefine the API to return character positions and all that,
but please don't complain that it's broken just because you happen to be
using it incorrectly. Use the right tool for the job. SQL for database
queries, non-home-brewed crypto libraries for security, regular
expressions for string manipulation.

I'm terribly sorry for the rant but I had to get it off my chest.

Dan

[Daniel DeLorme]

Greg Willits wrote:
> Greg Willits wrote:
>
>> I'm expecting a validate_format_of with a regex like this
>> /^[a-zA-Z\xC0-\xD6\xD9-\xF6\xF9-\xFF\.\'\-\ ]*?$/
>> to allow many of the normal characters like ö é å to be submitted via
>> web form. However, the extended characters are being rejected.
>
>
> So, I've been pounding the web for info on UTF8 in Ruby and Rails the
> past couple days to concoct some validations that allow UTF8
> characters. I have discovered that I can get a little further by doing
> the
> following:
> - declaring $KCODE = 'UTF8'
> - adding /u to regex expressions.
>
> The only thing not working now is the ability to define a range of \x
> characters in a regex.
>
> So, this /^[a-zA-Z\xE4]*?&/u will validate that a string is allowed
> to have an ä in it. Perfect.
>
> But... this fails /^[a-zA-Z\xE4-\xE6]*?&/u
>
> But... this works /^[a-zA-Z\xE4\xE5\xE6]*?&/u
>
> I've boiled the experiments down to realizing I can't define a range
> with \x
>
> Is this just one of those things that just doesn't work yet WRT Ruby/
> Rails/UTF8, or is there another syntax? I've scoured all the regex
> docs I can find, and they seem to indicate a range should work.

Let me try to explain that in order to redeem myself from my previous
angry post.

Basically, \xE4 is counted as the byte value 0xE4, not the unicode
character U+00E4. And in a range expression, each escaped value is taken
as one character within the range. Which results in not-immediately
obvious situations:

>> 'aébvHögtåwHÅFuG'.scan(/[\303\251]/u)
=> []
>> 'aébvHögtåwHÅFuG'.scan(/[#{"\303\251"}]/u)
=> ["é"]

What is happening in the first case is that the string does not contain
characters \303 or \251 because those are invalid utf8 sequences. But
when the value "\303\251" is *inlined* into the regex, that is
recognized as the utf8 character "é" and a match is found.

So ranges *do* work in utf8 but you have to be careful:

>> "àâäçèéêîïôü".scan(/[ä-î]/u)
=> ["ä", "ç", "è", "é", "ê", "î"]
>> "àâäçèéêîïôü".scan(/[\303\244-\303\256]/u)
=> ["\303", "\303", "\303", "\244", "\303", "\247", "\303", "\250",
"\303", "\251", "\303", "\252", "\303", "\256", "\303", "\257", "\303",
"\264", "\303", "\274"]
>> "àâäçèéêîïôü".scan(/[#{"\303\244-\303\256"}]/u)
=> ["ä", "ç", "è", "é", "ê", "î"]

Hope this helps.

Dan

[MonkeeSage]

This seems to work...

$KCODE = "UTF8"
p /^[a-zA-Z\xC0-\xD6\xD9-\xF6\xF9-\xFF\.\'\-\ ]*?/u =~ "Jäsp...it
works"
# => 0

However, it looks to me like it would be more robust to use a slightly
modified version of UTF8REGEX (found in the link Jimmy posted
above)...

UTF8REGEX = /\A(?:
[a-zA-Z\.\-\'\ ]
| [\xC2-\xDF][\x80-\xBF]
| \xE0[\xA0-\xBF][\x80-\xBF]
| [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}
| \xED[\x80-\x9F][\x80-\xBF]
| \xF0[\x90-\xBF][\x80-\xBF]{2}
| [\xF1-\xF3][\x80-\xBF]{3}
| \xF4[\x80-\x8F][\x80-\xBF]{2}
)*\z/mnx

p UTF8REGEX =~ "Jäsp...it works here too"
# => 0

Look at the link to see the explanation of the alternations.

Regards,
Jordan

[Daniel DeLorme]

Greg Willits wrote:
> So, this /^[a-zA-Z\xE4]*?&/u will validate that a string is allowed
> to have an ä in it. Perfect.

If that actually works, it means you are really using ISO-8859-1
strings, not UTF-8.

> utf_accents = '\xC0\xC1\xC2\.......'

Nope, that's not UTF-8. UTF-8 characters ÀÁÂ would look like
utf_accents = "\xC3\x80\xC3\x81\xC3\x82..."

Dan

[Greg Willits]

Daniel DeLorme wrote:
> Greg Willits wrote:

>> But... this fails /^[a-zA-Z\xE4-\xE6]*?&/u
>> But... this works /^[a-zA-Z\xE4\xE5\xE6]*?&/u
>>
>> I've boiled the experiments down to realizing I can't define a range
>> with \x

> Let me try to explain that in order to redeem myself from my previous
> angry post.

:-)

> Basically, \xE4 is counted as the byte value 0xE4, not the unicode
> character U+00E4. And in a range expression, each escaped value is taken
> as one character within the range. Which results in not-immediately
> obvious situations:
>
> >> 'aébvHögtåwHÅFuG'.scan(/[\303\251]/u)
> => []
> >> 'aébvHögtåwHÅFuG'.scan(/[#{"\303\251"}]/u)
> => ["é"]

OK, I see oniguruma docs refer to \x as encoded byte value and \x{} as a
character code point -- which with your explanation I can finally tie
together what that means.

Took me a second to recognize the #{} as Ruby and not some new regex I'd
never seen :-P

And I realize now too I wasn't picking up on the use of octal vs
decimal.

Seems like Ruby doesn't like to use the hex \x{7HHHHHHH} variant?

> What is happening in the first case is that the string does not contain
> characters \303 or \251 because those are invalid utf8 sequences. But
> when the value "\303\251" is *inlined* into the regex, that is
> recognized as the utf8 character "é" and a match is found.
>
> So ranges *do* work in utf8 but you have to be careful:
>
> >> "àâäçèéêîïôü".scan(/[ä-î]/u)
> => ["ä", "ç", "è", "é", "ê", "î"]
> >> "àâäçèéêîïôü".scan(/[\303\244-\303\256]/u)
> => ["\303", "\303", "\303", "\244", "\303", "\247", "\303", "\250",
> "\303", "\251", "\303", "\252", "\303", "\256", "\303", "\257", "\303",
> "\264", "\303", "\274"]
> >> "àâäçèéêîïôü".scan(/[#{"\303\244-\303\256"}]/u)
> => ["ä", "ç", "è", "é", "ê", "î"]
>
> Hope this helps.

Yes!

-- gw

[Greg Willits]

>> Basically, \xE4 is counted as the byte value 0xE4, not the unicode
>> character U+00E4. And in a range expression, each escaped value is taken
>> as one character within the range. Which results in not-immediately
>> obvious situations:
>>
>> >> 'aébvHögtåwHÅFuG'.scan(/[\303\251]/u)
>> => []
>> >> 'aébvHögtåwHÅFuG'.scan(/[#{"\303\251"}]/u)
>> => ["é"]

OK, one thing I'm still confused about -- when I look up é in any table,
it's DEC is 233 which converted to OCT is 351, yet you're using 251 (and
indeed it seems like reducing the OCTs I come up with by 100 is what
actually works).

Where is this 100 difference coming from?

[Phrogz]

On Dec 3, 2:07 pm, Greg Willits <li...@gregwillits.ws> wrote:
> >> >> 'aébvHögtåwHÅFuG'.scan(/[\303\251]/u)
> >> => []
> >> >> 'aébvHögtåwHÅFuG'.scan(/[#{"\303\251"}]/u)
> >> => ["é"]
>
> OK, one thing I'm still confused about -- when I look up é in any table,
> it's DEC is 233 which converted to OCT is 351, yet you're using 251 (and
> indeed it seems like reducing the OCTs I come up with by 100 is what
> actually works).
>
> Where is this 100 difference coming from?

http://www.fileformat.info/info/unicode/char/00e9/index.htm

The UTF-16 value is 233 (decimal), but the UTF-8 value is 0xC3 0xA9,
which is 195 169 in decimal, or 0303 0251 in octal.

[Phrogz]

[Charles Oliver Nutter]

Daniel DeLorme wrote:
> Usually the complaint about the support lack of unicode support is that
> something like "日本語".length returns 9 instead of 3, or that "日本語
> ".index("語") returns 6 instead of 2. It's nice that people want to
> completely redefine the API to return character positions and all that,
> but please don't complain that it's broken just because you happen to be
> using it incorrectly. Use the right tool for the job. SQL for database
> queries, non-home-brewed crypto libraries for security, regular
> expressions for string manipulation.
>
> I'm terribly sorry for the rant but I had to get it off my chest.

Regular expressions for all character work would be a *terribly* slow
way to get things done. If you want to get the nth character, should you
do a match for n-1 characters and a group to grab the nth? Or would it
be better if you could just index into the string and have it do the
right thing? How about if you want to iterate over all characters in a
string? Should the iterating code have to know about the encoding?
Should you use a regex to peel off one character at a time? Absurd.

Regex for string access goes a long way, but's just about the heaviest
way to do it. Strings should be aware of their encoding and should be
able to provide you access to characters as easily as bytes. That's what
1.9 (and upcoming changes in JRuby) fixes.

- Charlie

[MonkeeSage]

I missed your ranting.

Firstly, ruby doesn't have unicode support in 1.8, since unicode *IS*
a standard mapping of bytes to *characters*. That's what unicode is.
I'm sorry you don't like that, but don't lie and say ruby 1.8 supports
unicode when it knows nothing about that standard mapping and treats
everything as individual bytes (and any byte with a value greater than
126 just prints an octal escape); and please don't accuse others of
spreading FUD when they state the facts.

Secondly, as I said in my first post to this thread, the characters
trying to be matched are composite characters, which requires you to
match both bytes. You can try to using a unicode regexp, but then you
run into the problem you mention--the regexp engine expects the pre-
composed, one-byte form...

"ò".scan(/[\303\262]/u) # => []
"ò".scan(/[\xf2]/u) # => ["\303\262"]

...which is why I said it's more robust to use something like the the
regexp that Jimmy linked to and I reposted, instead of a unicode
regexp.

Regards,
Jordan

[MonkeeSage]

Oniguruma is not in ruby 1.8 (though you can install it as a gem). It
is in 1.9.

[Greg Willits]

Jordan Callicoat wrote:
> On Dec 3, 1:47 pm, Greg Willits <li...@gregwillits.ws> wrote:

>> :-)

>>
>> Seems like Ruby doesn't like to use the hex \x{7HHHHHHH} variant?
> Oniguruma is not in ruby 1.8 (though you can install it as a gem). It
> is in 1.9.

Oh. I always thought Oniguruma was the engine in Ruby.

Anyway -- everyone, thanks for all the input. I believe I'm headed in
the right direction now, and have a better hands on understanding of
UTF-8.

[Daniel DeLorme]

Charles Oliver Nutter wrote:
> Regular expressions for all character work would be a *terribly* slow
> way to get things done. If you want to get the nth character, should you
> do a match for n-1 characters and a group to grab the nth? Or would it
> be better if you could just index into the string and have it do the

Ok, I'm not very familiar with the internal working of strings in 1.9,
but it seems to me that for character sets with variable byte size, it
is logically *impossible* to directly index into the string. Unless
there's some trick I'm unaware of, you *have* to count from the
beginning of the string for utf8 strings.

> right thing? How about if you want to iterate over all characters in a
> string? Should the iterating code have to know about the encoding?
> Should you use a regex to peel off one character at a time?

That is certainly one possible way of doing things...
string.scan(/./){ |char| do_someting_with(char) }

> Regex for string access goes a long way, but's just about the heaviest
> way to do it.

Heavy compared to what? Once compiled, regex are orders of magnitude
faster than jumping in and out of ruby interpreted code.

> Strings should be aware of their encoding and should be
> able to provide you access to characters as easily as bytes. That's what
> 1.9 (and upcoming changes in JRuby) fixes.

Overall I agree that the encoding stuff in 1.9 is very nice.
Encapsulating the encoding with the string is very OO. Very intuitive.
No need to think about encoding anymore, now it "just works" for
encoding-ignorant programmers (at least until the abstraction leaks). It
allows to shut up one frequent complaint about ruby; a clear political
victory. Overall it is more robust and less error-prone than the 1.8 way.

But my point was that there *is* a 1.8 way. The thing that riled me up
and that I was responding to was the claim that 1.8 did not have unicode
support AT ALL. Unequivocally, it does, and it works pretty well for me.
IMHO there is a certain minimalist elegance in considering strings as
encoding-agnostic and using regex to get encoding-specific views. I
could do str[/./n] and str[/./u]; I can't do that anymore.

1.9 makes encodings easier for the english-speaking masses not used to
extended characters, but let's remember that ruby *always* had support
for multibyte character sets; after all it *did* originate from a
country with two gazillion "characters".

Daniel

[Daniel DeLorme]

MonkeeSage wrote:
> Firstly, ruby doesn't have unicode support in 1.8, since unicode *IS*
> a standard mapping of bytes to *characters*. That's what unicode is.
> I'm sorry you don't like that, but don't lie and say ruby 1.8 supports
> unicode when it knows nothing about that standard mapping and treats
> everything as individual bytes (and any byte with a value greater than
> 126 just prints an octal escape)

Ok, then how do you explain this:
>> $KCODE='u'
=> "u"
>> "abc\303\244".scan(/./)
=> ["a", "b", "c", "ä"]

This doesn't require any libraries, and it seems to my eyes that ruby is
converting 5 bytes into 4 characters. It shows an awareness of utf8. If
that's not *some* kind of unicode support then please tell me what it
is. It seem were disagreeing on some basic definition of what "unicode
support" means.

> Secondly, as I said in my first post to this thread, the characters
> trying to be matched are composite characters, which requires you to
> match both bytes. You can try to using a unicode regexp, but then you
> run into the problem you mention--the regexp engine expects the pre-
> composed, one-byte form...
>
> "ò".scan(/[\303\262]/u) # => []
> "ò".scan(/[\xf2]/u) # => ["\303\262"]

Wow, I never knew that second one could work. Unicode support is
actually better than I thought! You learn something new every day.

> ...which is why I said it's more robust to use something like the the
> regexp that Jimmy linked to and I reposted, instead of a unicode
> regexp.

I'm not sure what makes that huge regexp more robust than a simple
unicode regexp.

Daniel

[MonkeeSage]

On Dec 4, 3:07 am, Daniel DeLorme <dan...@dan42.com> wrote:

> Ok, then how do you explain this:
> >> $KCODE='u'
> => "u"
> >> "abc\303\244".scan(/./)
> => ["a", "b", "c", "ä"]
>
> This doesn't require any libraries, and it seems to my eyes that ruby is
> converting 5 bytes into 4 characters. It shows an awareness of utf8. If
> that's not *some* kind of unicode support then please tell me what it
> is. It seem were disagreeing on some basic definition of what "unicode
> support" means.

I guess we were talking about different things then. I never meant to
imply that the regexp engine can't match unicode characters (it's
"dumb" implementation though; it basically only knows that bytes above
127 can have more bytes following and should be grouped together as
candidates for a match; that's slightly simplified, but basically
accurate).

I, like Charles (and I think most people), was referring to the
ability to index into strings by characters, find their lengths in
characters, to compose and decompose composite characters, to
normalize characters, convert them to other encodings like shift-jis,
and other such things. Ruby 1.9 has started adding such support, while
ruby 1.8 lacks it. It can be hacked together with regular expressions
(e.g., the link Jimmy posted), or even as a real, compiled extension
[1], but merely saying that *you* the programmer can implement it
using ruby 1.8, is not the same thing as saying ruby 1.8 supports it
(just like I could build a python VM in ruby, but that doesn't mean
that the ruby interpreter runs python bytecode). Anyhow, I guess it's
just a difference of opinion. I don't mind being wrong (happens a
lot! ;) I just don't like being accused of spreading FUD about ruby,
which to my mind implies malice of forethought rather that simply
mistake.

[1] http://rubyforge.org/projects/char-encodings/
http://git.bitwi.se/ruby-character-encodings.git/

> > Secondly, as I said in my first post to this thread, the characters
> > trying to be matched are composite characters, which requires you to
> > match both bytes. You can try to using a unicode regexp, but then you
> > run into the problem you mention--the regexp engine expects the pre-
> > composed, one-byte form...
>
> > "ò".scan(/[\303\262]/u) # => []
> > "ò".scan(/[\xf2]/u) # => ["\303\262"]
>
> Wow, I never knew that second one could work. Unicode support is
> actually better than I thought! You learn something new every day.
>
> > ...which is why I said it's more robust to use something like the the
> > regexp that Jimmy linked to and I reposted, instead of a unicode
> > regexp.
>
> I'm not sure what makes that huge regexp more robust than a simple
> unicode regexp.
>
> Daniel

Well, I won't claim that you can't get a unicode regexp to match the
same. And I only saw that large regexp when it was posted here, so
I've not tested it to any great length. Interestingly, 1.9 uses this
regexp (originally from jcode.rb in stdlib) to classify a string as
containing utf-8: '[\xc0-\xdf][\x80-\xbf]|[\xe0-\xef][\x80-\xbf][\x80-
\xbf]'. My thought was that without knowing all of the minute
intricacies of unicode and how ruby strings and regexps work with
unicode values (which I don't, and assume the OP doesn't), I think the
huge regexp is more likely to Just Work in more cases than a home-
brewed unicode regexp. But like I said, that's just an initial
conclusion, I don't claim it's absolutely correct.

Regards,
Jordan

[Daniel DeLorme]

MonkeeSage wrote:
> I guess we were talking about different things then. I never meant to
> imply that the regexp engine can't match unicode characters

Since regular expressions are embedded in the very syntax of ruby just
as arrays and hashes, IMHO that qualifies as unicode support. So yeah,
it seems like we have a semantic disagreement. :-(

> I, like Charles (and I think most people), was referring to the
> ability to index into strings by characters, find their lengths in
> characters

That is certainly *one* way of supporting unicodde but by no means the
only way. My belief is that you can do most string manipulations in a
way that obviates the need for char indexing & char length, if only you
change your mindset from "operating on individual characters" to
"operating on the string as a whole". And since regex are a specialized
language for string manipulation, they're also a lot faster. It's a
little like imperative vs functional programming; if I told you about a
programming language that has no variable assignments you might think
it's completely broken, and yet that's how functional languages work.

> to compose and decompose composite characters, to
> normalize characters, convert them to other encodings like shift-jis,
> and other such things.

Converting encodings is a worthy goal but unrelated to unicode support.
As for character [de]composition that would be a very nice thing to have
if it was handled automatically (e.g. "a\314\200"=="\303\240") but if
the programmer has to worry about it then you might as well leave it to
a specialized library. Well, it's not like ruby lets us abstract away
composite characters either in 1.8 or 1.9... I never claimed unicode
support was 100%, just good enough for most needs.

> just a difference of opinion. I don't mind being wrong (happens a
> lot! ;) I just don't like being accused of spreading FUD about ruby,
> which to my mind implies malice of forethought rather that simply
> mistake.

Yes, that was too harsh on my part. My apologies.

Daniel

[Daniel DeLorme]

Daniel DeLorme wrote:
> Heavy compared to what? Once compiled, regex are orders of magnitude
> faster than jumping in and out of ruby interpreted code.

Sorry to beat a dead horse, but I just did an interesting little
experiment with 1.9:

>> str = "abcde"*1000
>> str.encoding
=> <Encoding:ASCII-8BIT>
>> Benchmark.measure{10.times{ 1000.times{|i|str[i]} }}.real
=> 0.010282039642334
>> str.force_encoding 'utf-8'
>> Benchmark.measure{10.times{ 1000.times{|i|str[i]} }}.real
=> 1.29934501647949
>> arr = str.scan(/./u)
>> Benchmark.measure{10.times{ 1000.times{|i|arr[i]} }}.real
=> 0.00343608856201172

indexing into UTF-8 strings is *expensive*

Daniel

[Charles Oliver Nutter]

..but correct. I'd rather have correct than broken.

- Charlie

[MonkeeSage]

On Dec 4, 7:58 pm, Daniel DeLorme <dan...@dan42.com> wrote:
> MonkeeSage wrote:
> > I guess we were talking about different things then. I never meant to
> > imply that the regexp engine can't match unicode characters
>
> Since regular expressions are embedded in the very syntax of ruby just
> as arrays and hashes, IMHO that qualifies as unicode support. So yeah,
> it seems like we have a semantic disagreement. :-(
>
> > I, like Charles (and I think most people), was referring to the
> > ability to index into strings by characters, find their lengths in
> > characters
>
> That is certainly *one* way of supporting unicodde but by no means the
> only way. My belief is that you can do most string manipulations in a
> way that obviates the need for char indexing & char length, if only you
> change your mindset from "operating on individual characters" to
> "operating on the string as a whole". And since regex are a specialized
> language for string manipulation, they're also a lot faster. It's a
> little like imperative vs functional programming; if I told you about a
> programming language that has no variable assignments you might think
> it's completely broken, and yet that's how functional languages work.

I think we'll just have to agree to disagree. But there is one
point...

main = do
let i_like = "I like "
putStrLn $ i_like ++ haskell
where haskell = "a functional language"

;)

> > to compose and decompose composite characters, to
> > normalize characters, convert them to other encodings like shift-jis,
> > and other such things.
>
> Converting encodings is a worthy goal but unrelated to unicode support.
> As for character [de]composition that would be a very nice thing to have
> if it was handled automatically (e.g. "a\314\200"=="\303\240") but if
> the programmer has to worry about it then you might as well leave it to
> a specialized library. Well, it's not like ruby lets us abstract away
> composite characters either in 1.8 or 1.9... I never claimed unicode
> support was 100%, just good enough for most needs.
>
> > just a difference of opinion. I don't mind being wrong (happens a
> > lot! ;) I just don't like being accused of spreading FUD about ruby,
> > which to my mind implies malice of forethought rather that simply
> > mistake.
>
> Yes, that was too harsh on my part. My apologies.

No worries. :) I apologize as well for responding by saying you were
lying about unicode support; I see that we just have a difference of
opinion and were talking past each another.

> Daniel

Regards,
Jordan

[marc]

Daniel DeLorme said...

> MonkeeSage wrote:
> > Ruby 1.8 doesn't have unicode support (1.9 is starting to get it).
>
> I enrages me to see this kind of FUD. Through regular expressions, ruby
> 1.8 has 80-90% complete utf8 support. And oniguruma makes utf8 support
> well-near 100% complete.
>
>

> > Everything in ruby is a bytestring.
>
> YES! And that's exactyly how it should be. Who is it that spread the
> flawed idea that strings are fundamentally made of characters?

Are you being ironic?

> I'd like
> to slap him around a little. Fundamentally, ever since the word "string"
> was applied to computing, strings were made of 8-BIT CHARS, not n-bit
> characters. If only the creators of C has called that datatype "byte"
> instead of "char" it would have saved us so many misunderstandings.

And look at the trouble we're having ditching the waterfall method, all
because someone misread a paper in the 1700s or thereabouts.

You might want to spar with Tim Bray from Sun who presented at RubyConf
2006, where his slides state:

"99.99999% of the time, programmers want to deal with characters not
bytes. I know of one exception: running a state machine on UTF8-encoded
text. This is done by the Expat XML parser."

"In 2006, programmers around the world expect that, in modern languages,
strings are Unicode and string APIs provide Unicode semantics correctly
& efficiently, by default. Otherwise, they perceive this as an offense
against their language and their culture. Humanities/computing academics
often need to work outside Unicode. Few others do."

He reviews his chat here:

http://www.tbray.org/ongoing/When/200x/2006/10/22/Unicode-and-Ruby

and the slides are here:

http://www.tbray.org/talks/rubyconf2006.pdf

--
Cheers,
Marc

[Daniel DeLorme]

marc wrote:
> Daniel DeLorme said...
>> MonkeeSage wrote:
>>> Everything in ruby is a bytestring.
>> YES! And that's exactyly how it should be. Who is it that spread the
>> flawed idea that strings are fundamentally made of characters?
>
> Are you being ironic?

Not at all. By "fundamentally" I mean the fundamental, lowest level of
representation. If strings were fundamentally made of characters then we
wouldn't be able to access individual bytes because that's a lower level
than the fundamental level, which is by definition impossible.

If you are using UCS2 it makes sense to consider strings as arrays of
characters because that's what they are. But UTF8 strings do not follow
the characteristics of arrays at all. Each access into the "array" is
O(n) rather than O(1). So IMHO treating it as an array of characters is
a *very* leaky abstraction.

I agree that 99.9% of the time you want to deal with characters, and I
believe that in 99% of those cases you would be better served with regex
than this pretend "array" disguise.

Daniel

[MonkeeSage]

Here is a micro-benchmark on three common string operations (split,
index, length), using bytestrings and unicode regexp, verses native
utf-8 strings in 1.9.0 (release).

$ ruby19 -v
ruby 1.9.0 (2007-10-15 patchlevel 0) [i686-linux]

$ echo && cat bench.rb
#!/usr/bin/ruby19
# -*- coding: ascii -*-

require "benchmark"
require "test/unit/assertions"
include Test::Unit::Assertions

$KCODE = "u"

$target = "!日本語!" * 100
$unichr = "本".force_encoding('utf-8')
$regchr = /[本]/u

def uni_split
$target.split($unichr)
end
def reg_split
$target.split($regchr)
end

def uni_index
$target.index($unichr)
end
def reg_index
$target =~ $regchr
end

def uni_chars
$target.length
end
def reg_chars
$target.unpack("U*").length
# this is *alot* slower
# $target.scan(/./u).length
end

$target.force_encoding("ascii")
a = reg_split
$target.force_encoding("utf-8")
b = uni_split
assert_equal(a.length, b.length)

$target.force_encoding("ascii")
a = reg_index
$target.force_encoding("utf-8")
b = uni_index
assert_equal(a-2, b)

$target.force_encoding("ascii")
a = reg_chars
$target.force_encoding("utf-8")
b = uni_chars
assert_equal(a, b)

n = 10_000
Benchmark.bm(12) { | x |
$target.force_encoding("ascii")
x.report("reg_split") { n.times { reg_split } }
$target.force_encoding("utf-8")
x.report("uni_split") { n.times { uni_split } }
puts
$target.force_encoding("ascii")
x.report("reg_index") { n.times { reg_index } }
$target.force_encoding("utf-8")
x.report("uni_index") { n.times { uni_index } }
puts
$target.force_encoding("ascii")
x.report("reg_chars") { n.times { reg_chars } }
$target.force_encoding("utf-8")
x.report("uni_chars") { n.times { uni_chars } }
}

====

With caches initialized, an 5 prior runs, I got these numbers:

$ ruby19 bench.rb
user system total real
reg_split 2.550000 0.010000 2.560000 ( 2.799292)
uni_split 1.820000 0.020000 1.840000 ( 2.026265)

reg_index 0.040000 0.000000 0.040000 ( 0.097672)
uni_index 0.150000 0.000000 0.150000 ( 0.202700)

reg_chars 0.790000 0.010000 0.800000 ( 0.919995)
uni_chars 0.130000 0.000000 0.130000 ( 0.193307)

====

So String#=~ with a bytestring and unicode regexp is faster than
String#index by a fator or ~0.5. In the other two cases, the opposite
is true.

Ps. BTW, in case there is any confusion, bytestrings aren't going
away; you can, as you see above, specify a magic encoding comment to
ensure that you have bytestrings by default. You can also explicitly
decode from utf-8 back to ascii. and you can get a byte enumerator (or
array from calling to_a on the enumerator) from String#bytes, and an
iterator from #each_byte, irregardless of the encoding.

Regards,
Jordan

[Daniel DeLorme]

MonkeeSage wrote:
> Here is a micro-benchmark on three common string operations (split,
> index, length), using bytestrings and unicode regexp, verses native
> utf-8 strings in 1.9.0 (release).

That's nice, but split and index do not operate using integer indexing
into the string, so they are rather irrelevant to the topic at hand.
They produce the same results in ruby1.8, i.e. uni_split==reg_split and
uni_index==reg_index.

I also stated that the point of regex manipulation is to *obviate* the
need for methods like index and length. So a more accurate benchmark
might be something like:
reg_chars N/A N/A N/A ( N/A )

uni_chars 0.130000 0.000000 0.130000 ( 0.193307)

;-)

> Ps. BTW, in case there is any confusion, bytestrings aren't going
> away; you can, as you see above, specify a magic encoding comment to
> ensure that you have bytestrings by default.

Yes, it's still possible to access bytes but it's not possible to run a
utf8 regex on a bytestring if it contains extended characters:

$ ruby1.9 -ve '"abc" =~ /b/u'
ruby 1.9.0 (2007-12-03 patchlevel 0) [i686-linux]
$ ruby1.9 -ve '"日本語" =~ /本/u'
ruby 1.9.0 (2007-12-03 patchlevel 0) [i686-linux]
-e:1:in `<main>': character encodings differ (ArgumentError)

And that kinda kills my whole approach.

Daniel

[MonkeeSage]

On Dec 5, 8:31 pm, Daniel DeLorme <dan...@dan42.com> wrote:
> MonkeeSage wrote:
> > Here is a micro-benchmark on three common string operations (split,
> > index, length), using bytestrings and unicode regexp, verses native
> > utf-8 strings in 1.9.0 (release).
>
> That's nice, but split and index do not operate using integer indexing
> into the string, so they are rather irrelevant to the topic at hand.

Heh, if the topic at hand is only that indexing into a string is
slower with native utf-8 strings (don't disagree), then I guess it's
irrelevant. ;) Regarding the idea that you can do everything just as
efficiently with regexps that you can do with native utf-8
encoding...it seems relevant. In other words, it goes to show a
general behavior that is benefited by a native implementation (the
same reason we're using native hashes rather than building our own
implementations out of arrays of pairs).

> They produce the same results in ruby1.8, i.e. uni_split==reg_split and
> uni_index==reg_index.

Yes. My point was to show how a native implementation of unicode
strings effects performance compared to using regular expressions on
bytestrings. The behavior should be the same (hence the asserts).

> I also stated that the point of regex manipulation is to *obviate* the
> need for methods like index and length. So a more accurate benchmark
> might be something like:
> reg_chars N/A N/A N/A ( N/A )
> uni_chars 0.130000 0.000000 0.130000 ( 0.193307)
> ;-)

Someone just posted a question today about how to printf("%20s ...",
a, ...) when "a" contains unicode (it screws up the alignment since
printf only counts byte width, not character width). There is no
*elegant* solution in 1.8., regexps or otherwise. There are haskish
solutions (I provided one in that thread)...but the need was still
there. Another example is GtkTextView widgets from ruby-gtk2. They
deal with utf-8 in their C backend. So all the cursor functions that
deal with characters mean utf-8 characters, not bytestrings. So
without kludges, stuff doesn't always work right.

> > Ps. BTW, in case there is any confusion, bytestrings aren't going
> > away; you can, as you see above, specify a magic encoding comment to
> > ensure that you have bytestrings by default.
>
> Yes, it's still possible to access bytes but it's not possible to run a
> utf8 regex on a bytestring if it contains extended characters:
>
> $ ruby1.9 -ve '"abc" =~ /b/u'
> ruby 1.9.0 (2007-12-03 patchlevel 0) [i686-linux]
> $ ruby1.9 -ve '"日本語" =~ /本/u'
> ruby 1.9.0 (2007-12-03 patchlevel 0) [i686-linux]
> -e:1:in `<main>': character encodings differ (ArgumentError)
>
> And that kinda kills my whole approach.

You can't use mixed encodings (not just in regexps, not anywhere).
You'd have to use a proposed-but-not-implemented-in-1.9.0-release,
command line switch to set your encoding to ascii (or whatever), or
else use a magic comment [1] like I did above. That or explicitly
encode both objects in the same encoding.

> Daniel

Regards,
Jordan

[1] http://www.ruby-forum.com/topic/127831

[Daniel DeLorme]

MonkeeSage wrote:
> Heh, if the topic at hand is only that indexing into a string is
> slower with native utf-8 strings (don't disagree), then I guess it's
> irrelevant. ;) Regarding the idea that you can do everything just as
> efficiently with regexps that you can do with native utf-8
> encoding...it seems relevant.

How so? These methods work just as well in ruby1.8 which does *not* have
native utf8 encoding embedded in the strings. Of course, comparing a
string with a string is more efficient than comparing a string with a
regexp, but that is irrelevant of whether the string has "native" utf8
encoding or not:

$ ruby1.8 -rbenchmark -KU
puts Benchmark.measure{100000.times{ "日本語".index("本") }}.real
puts Benchmark.measure{100000.times{ "日本語".index(/[本]/) }}.real
puts Benchmark.measure{100000.times{ "日本語".index(/[本]/u) }}.real
^D
0.225839138031006
0.304145097732544
0.313494920730591

$ ruby1.9 -rbenchmark -KU
puts Benchmark.measure{100000.times{ "日本語".index("本") }}.real
puts Benchmark.measure{100000.times{ "日本語".index(/[本]/) }}.real
puts Benchmark.measure{100000.times{ "日本語".index(/[本]/u) }}.real
^D
0.183344841003418
0.255104064941406
0.263553857803345

1.9 is more performant (one would hope so!) but the performance ratio
between string comparison and regex comparison does not seem affected by
the encoding at all.

> Someone just posted a question today about how to printf("%20s ...",
> a, ...) when "a" contains unicode (it screws up the alignment since
> printf only counts byte width, not character width). There is no
> *elegant* solution in 1.8., regexps or otherwise.

It's not perfect in 1.9 either. "%20s" % "日本語" results in a string of
20 characters... that uses 23 columns of terminal space because the font
for Japanese uses double width. In other words neither bytes nor
characters have an intrinsic "width" :-/

Daniel

[MonkeeSage]

Ok, I wasn't being clear. What I was trying to say is, yes the methods
perform the same on bytestrings -- whether using regex or standard
string operations. The problem is in their behavior, not performance
considered in the abstract. In 1.9, using ascii default encoding, this
bytestring acts just like 1.8:

"日本語".index("本") #=> 3

That's fine! Faster than a regexp, no problems. That is, unless I want
to know where the character match is (for whatever reason -- take work-
necessitated interoperability with some software that required it).
For that I'd have to do something hackish and likely fragile. It's
possible, but not desirable; however, being able to do this gains
performance and ruby already does all the work for you:

"日本語".force_encoding("utf-8").index("本".force_encoding("utf-8")) #=> 1

But it's obviously not better to type! But that's because I'm using
ascii default encoding. There is, as I understand it, going to be a
way to specify default encoding from the command-line, and probably
from within ruby, rather than just the magic comments and
String#force_encoding; so this extra typing is incidental and will go
away. Actually, it goes away right now if you use utf-8 default and
use the byte api to get at the underlying bytestrings.

> > Someone just posted a question today about how to printf("%20s ...",
> > a, ...) when "a" contains unicode (it screws up the alignment since
> > printf only counts byte width, not character width). There is no
> > *elegant* solution in 1.8., regexps or otherwise.
>
> It's not perfect in 1.9 either. "%20s" % "日本語" results in a string of
> 20 characters... that uses 23 columns of terminal space because the font
> for Japanese uses double width. In other words neither bytes nor
> characters have an intrinsic "width" :-/
>
> Daniel

It works as expected in 1.9, you just have to set the right encoding:

printf("%20s\n".force_encoding("utf-8"),
"ni\xc3\xb1o".force_encoding("utf-8"))
#=> niño

printf("%20s\n", "nino")
#=> niño

Any case, I just don't think there is any reason to dislike the new
string api. It adds another tool to the toolbox. It doesn't make sense
to use it always, everywhere (like trying to make data that naturally
has the shape of an array, fit into a hash); but I see no reason to
try and cobble it together ourselves either (like building a hash api
from arrays ourselves). And with that, I'm going to sleep. Have to
think more on it tomorrow.

Peace,
Jordan

[Jimmy Kofler]

> Re: Unicode in Regex
> Posted by Jordan Callicoat (monkeesage) on 03.12.2007 02:50

>
> This seems to work...
>
> $KCODE = "UTF8"

> p /^[a-zA-Z\xC0-\xD6\xD9-\xF6\xF9-\xFF\.\'\-\ ]*?/u =~ "J�sp...it works"
> # => 0
> ...

> However, it looks to me like it would be more robust to use a slightly
> modified version of UTF8REGEX (found in the link Jimmy posted
> above)...
>
> UTF8REGEX = /\A(?:
> [a-zA-Z\.\-\'\ ]
> | [\xC2-\xDF][\x80-\xBF]
> | \xE0[\xA0-\xBF][\x80-\xBF]
> | [\xE1-\xEC\xEE\xEF][\x80-\xBF]{2}
> | \xED[\x80-\x9F][\x80-\xBF]
> | \xF0[\x90-\xBF][\x80-\xBF]{2}
> | [\xF1-\xF3][\x80-\xBF]{3}
> | \xF4[\x80-\x8F][\x80-\xBF]{2}
> )*\z/mnx

Just to avoid confusion over the meaning of 'UTF8' in UTF8REGEX: the n
option sets the encoding of UTF8REGEX to none!

Cheers,

j. k.