16 ms·

The string type is broken

• Pitarou 13y ago
  Hat tip to Guido van Rossum for passing (nearly) all the tests in Python 3. Is the "ffl-ligature to uppercase" test really relevant? Isn't that fixed by appropriate use of string normalisation?
  • andrewcooke 13y ago
    [edit:] ah, ok, so on python 3 it depends how it's constructed. [originally i had a post here saying i couldn't get the noel to work on 3.3.2]
    • mercurial 13y ago
      Seems to work fine on 3.3.3 (Linux) Python 3.3.3 (default, Nov 23 2013, 09:49:26) [GCC 4.8.2] on linux Type "help", "copyright", "credits" or "license" for more information. >>> a = "noël" >>> len(a) 4 >>> a[::-1] 'lëon'
      • judofyr 13y ago
        This is the test case: https://eval.in/73766 https://eval.in/73766 print(len("noe\u0308l"))
        • mercurial 13y ago
          Ah, I see, the decomposed case indeed doesn't work as well.
    • masklinn 13y ago
      The test case is decomposed.
  • unwind 13y ago
    I also doubt the validity of the upper-casing, it feels like in an internationalization/localization context, converting a string to all upper case is not a valid thing to be doing. Not all languages (or even characters) have a well-defined upper-case versions of their glyphs. Even if they all did, I would expect the interpretation by a (human) reader to vary culturally.
    • judofyr 13y ago
      The Unicode standard includes uppercase rules. If you're already representing strings using Unicode codepoints, why not follow the whole Unicode standard? EDIT: And yes, different languages can have different uppercasing rules. There's still a standard: https://github.com/lang/unicode_utils/blob/master/data/CaseFolding.txt https://github.com/lang/unicode_utils/blob/master/data/CaseF...
      • unwind 13y ago
        Thanks, I was not aware of that. I guess "uppercase this string" goes from being a tiny loop to a big ... thing based on a lot of hardcoded knowledge, which in turn might indicate that it's not a very simple operation any more.
    • XorNot 13y ago
      The usual goal is to apply a consistent transform though, to smooth out interpretation differences - i.e. when looking for command input I either lowercase or uppercase things to smooth over the fact that "yes" "YES" "Yes" are all completely valid ways of saying the same thing with those characters. If there's only one way of expressing the thing - i.e. a single chinese character - then it would be valid to do nothing. It's just in english "y" and "Y" might change context, but as far as computer input is generally concerned they are the same thing.
      • TorKlingberg 13y ago
        For that use case it is better to compare case insensitively with "yes" instead of converting the input to lower case first.
  • riquito 13y ago
    The ffl ligature passes $ python3 Python 3.3.2+ (default, Oct 9 2013, 14:50:09) [GCC 4.8.1] on linux Type "help", "copyright", "credits" or "license" for more information. >>> "baffle".upper() 'BAFFLE' Strange that the article claims that no languages passes it. It seems from another post that perl passes it too
    • Pitarou 13y ago
      Embarrassing. I should have checked for myself. And it is strange. Maybe the author needs to check his locale settings?
• shioyama 13y ago
  Happy to see that ruby (2.0 at least) passes all the tests except the "baffle" one. Edit: sadly, it doesn't.
  • judofyr 13y ago
    "noe\u0308l".size # => 5 ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-darwin13.0.0]
    • shioyama 13y ago
      Ah, oops. I read the post too quickly, now I see the problem.
    • monkeyninja 13y ago
      "noe\u{0308}".size => 4 You code is wrong
      • judofyr 13y ago
        You forgot the "l": "noe\u{0308}" # => "noë"
  • mef 13y ago
    If you're using Rails, the ActiveSupport::Multibyte::Chars library (#mb_chars on any string) passes all these tests except the upcase of baffle: irb(main):001:0> RUBY_VERSION => "1.9.3" irb(main):002:0> Rails.version => "3.2.14" irb(main):003:0> # example 1 irb(main):004:0* example1 = "noe\u0308l".mb_chars => noël irb(main):005:0> example1.reverse => lëon irb(main):006:0> example1.compose.slice(0,3) => noë irb(main):007:0> example1.g_length #grapheme_length => 4 irb(main):008:0> example1.compose.length => 4 irb(main):009:0> # example 2 irb(main):010:0* example2 = "😸😾".mb_chars => 😸😾 irb(main):011:0> example2.length => 2 irb(main):012:0> example2.slice(1,1) => 😾 irb(main):013:0> example2.reverse => 😾😸 irb(main):014:0> # example 3 irb(main):015:0* example3 = "baffle".mb_chars => baffle irb(main):016:0> example3.upcase => BAfflE irb(main):017:0> # example 4 irb(main):018:0* example4 = "noël".mb_chars => noël irb(main):019:0> example4 == example1 => false irb(main):020:0> example4 == example1.compose => true
• judofyr 13y ago
  In many languages it's difficult fixing the string type without breaking existing code. In Ruby: String#upcase only handles ASCII (by spec), #length counts codepoints, #reverse reverses codepoints. You can use UnicodeUtils if you need "full" Unicode support: >> UnicodeUtils.upcase("baffle") => "BAFFLE" >> graphemes = UnicodeUtils.each_grapheme("noe\u0308l").to_a >> graphemes.reverse.join => "lëon" >> graphemes.size => 4 >> graphemes[0, 3] => "noë"
  • lelf 13y ago
    > String#upcase only handles ASCII (by spec) Bad for Ruby > You can use UnicodeUtils if you need "full" Unicode support: Oh, sure Betty:~ lelf$ ruby -r unicode_utils/u -e 'puts UnicodeUtils.each_grapheme("A‮͜CB‬D").to_a.reverse.join' D‬BC͜‮A So, "full" (it's not) Unicode support won't help you if you have little idea about what you're doing (like indexing stringه҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿҈̿s)
    • jhull 13y ago
      what are these characters printing here?
      • preek 13y ago
        It's an awesome little gadget - looks like one character, but is a really big messy bunch of bytes: "\xD9\x87\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\ x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD 2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\ xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xB F\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\ xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xC C\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\ xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x8 8\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\ x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD 2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\ xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xB F\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\ xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xCC\xBF\xD2\x88\xC C\xBF\n"
• tomp 13y ago
  The problem with text (that Unicode solves only partially) is that text representation, being a representation of human thought, in inherently ambiguous and imprecise. Some examples: (1) A == A but A != Α. The last letter is not uppercase "a", but uppercase "α". Most of the time, the difference is important, but sometimes humans want to ignore it (imagine you can't find an entry in a database since it contains Α that looks just like A). Google gives different autocomplete suggestions for A and Α. Is this outcome expected? is it desired? (2) The Turkish alphabet is mostly the same as the Latin alphabet, except for the letter "i", which exists in two variants: dotless ı and dotted i (as in Latin). For the sake of consistency, this distinction is kept in the upper case as well: dotless I (as in Latin) and dotted İ. We can see that not even the uppercase <==> lowercase transformation is defined for text independently of language. These are just two examples of problems with text processing that arise even before all the problems with Unicode (combining characters, ligatures, double-width characters, ...) and without considering all the conventions and exceptions that exist in richer (mostly Asian) alphabets.
  • taeric 13y ago
    I think your first assertion can be strengthened even further. It isn't like this is unique to letters that look the same. That is, sometimes WORD != WORD. Consider a few common words. Time? As in Time of day? As in how long you have? An interesting combination of the two? Day? As in a marker on the calendar? Just the time when the sun is out? Then we get into names. Imagine the joy of having to find someone named "Brad" that isn't famous. From a city named Atlanta, but not the one in GA. (If you really want some fun, consider the joy that is abbreviations. Dr?)
    • derleth 13y ago
      Except these are all well outside the ambit of what programmers usually think of as text processing, so they won't try to solve them using the same tools. More to the point, they sound hard, so people won't be so quick to claim they've solved them. On the other hand, case-insensitive string matching sounds easy, even if it's actually somewhat difficult due to the language dependencies mentioned above, so people will claim to have a general solution that fails the first time it's faced with i up-casing to İ instead of I, or the fact the German 'ß' up-cases to 'SS' as opposed to any single character. (Unicode does contain 'ẞ', a single-character capital 'ß', which occurs in the real world but is vanishingly rare. As far as modern German speakers are concerned, the capital form of 'ß' is 'SS'.) http://en.wikipedia.org/wiki/Capital_%E1%BA%9E http://en.wikipedia.org/wiki/Capital_%E1%BA%9E http://opentype.info/blog/2013/11/18/capital-sharp-s-design-review/ http://opentype.info/blog/2013/11/18/capital-sharp-s-design-... http://blogs.msdn.com/b/michkap/archive/2009/07/28/9850675.aspx http://blogs.msdn.com/b/michkap/archive/2009/07/28/9850675.a... http://www.personal.psu.edu/ejp10/blogs/gotunicode/2008/07/a-new-german-unicode-letter-ca.html http://www.personal.psu.edu/ejp10/blogs/gotunicode/2008/07/a...
• masklinn 13y ago
  I'm not sure I agree with the title, although I do agree with just about all of the content: * a string type is probably a good idea to bundle the subtleties of unicode, a plain array or list (whether it's of bytes or of codepoints) won't cut it: standard array operations are incorrect/invalid on unicode streams * the vast majority of string types are broken anyway, as even in the best case they're codepoint arrays (possibly with a smart implementation). The bad cases are just code unit arrays, which break before you even reach fine points of unicode manipulation And then, you've got the issue that a lot of unicode manipulation is locale-dependent, which most languages either ignore completely or fuck up (or half and half, for extra fun)
• lmm 13y ago
  I think the mistake here is seeing a string as an extension of an array or vector. What I would prefer is a string type that didn't support all the operations of vectors. The length of a string is not inherently a meaningful question (and for the cases where it is, what you want is something like a vector of grapheme clusters - which is a useful type to have, but not so useful that every string in your program should incur the overhead of creating such a thing); likewise reversing and splitting are operations that simply shouldn't be allowed for your "fast path, undecoded string" type.
  • rlpb 13y ago
    I'm with you here; but in that case, I'd like an ascii_string type, which most languages don't provide specifically. This type _would_ support string reversal, substring slices, and so on, but be limited to 7-bit ASCII only. I think there are many use cases that are purely internal, and don't need i8n. It's handy to be able to do things, including operations on strings, for internal things. Filename handling where you control the filename, the "keys" in languages which use strings for a dictionary type, and so forth.
    • jeltz 13y ago
      I think this might just confuse new programmers and the filename thing is especially dangerous since at some point you might want to support i18n there. I think it would be better to have two types of string: 1) unicode strings and 2) arrays of 8 byte data with some string like functions (essentially C strings). The second case is essentially binary data strings.
• davidhalter 13y ago
  I would argue that it's a unicode problem. `U+0308` shouldn't exist in the first place as a unicode character. That's why we have `U+00EB` ('LATIN SMALL LETTER E WITH DIAERESIS'), etc.
  • masklinn 13y ago
    Not all combination of base and combining characters exist in a precomposed form, since a base character can have an infinite number of combining characters tacked onto it. If anything should not exist, it's U+00EB, which is a convenience, compatibility and (space) optimisation codepoint.
  • ygra 13y ago
    Uhm, nope. Definitely not. All the precomposed letters only exist because of compatibility with legacy character sets. There are also some languages that routinely use more than one stacked diacritic on letters and encoding every possible precomposed variant would be at least a little bit silly.
  • zokier 13y ago
    I would argue the opposite. Combining characters are a general (and thus preferable) solution to diacritics, so precombined codepoints should not have been included in Unicode.
• drdaeman 13y ago
  That's because in a truly sane languages there should be a distinction between data type and its implementation. Then it would be not "string" type, that's broken, but an implementation of "string" type.
  • agravier 13y ago
    I agree, it seems like a much saner thing to do. Now that you make me think of that, I do not know many instances of this. I just could think of https://github.com/clojure-numerics/core.matrix https://github.com/clojure-numerics/core.matrix upon which I stumbled recently. Do you have other example of efforts to separate a type from its implementations?
    • lmm 13y ago
      Most collection libraries (e.g. the Java one) work like this - you have List as an interface and can use LinkedList or ArrayList or so on. I particularly like scala's approach to factory-like methods combined with this; Seq is an interface, as is List, with implementations like LinkedList. But you can do any of LinkedList(1, 2, 3), List(1, 2, 3), or Seq(1, 2, 3) - and get back a LinkedList, a List (which will be an implementation-selected implementation, possibly LinkedList), or a Seq (which again will be an implementation-selected implementation, possibly LinkedList).
    • riffraff 13y ago
      doesn't every statically typed imperative language do this, and recommend it?
      • drdaeman 13y ago
        Not to my knowledge. C++ and Java are statically typed and they, as far as I know, don't have distinction between string interface and implementation, just a standard string type. You can't make your own string implementation and make others (given that - would it exist - they use standard string interface) transparently accept them instead of language's standard string implementation. Even Haskell (with standard Prelude) doesn't have a readily available and widely accepted typeclass for strings. As String is just an alias to [Char], if library writer used that, they won't accept, say, Data.Text (I know, it's a bit distinct thing, but...)
• billpg 13y ago
  Do people really need to reverse strings in the real world? I don't think I've ever written code to do that outside of homework assignments and interviews.
  • markild 13y ago
    The same mechanism that is used for reversing a string can be very useful though. Think in the lines of python's: >>> 'abcd'[:-1] 'abc'
  • jmpe 13y ago
    Had such a case a few months back. Strings of single-byte characters are Endian-agnostic but multi-byte character encoding is affected by Endianness. To cope with it I read the sequence as single byte, then reversed, then changed the encoding to proper encoding and reversed again. The data came from a binary dump where I only needed a section that contained a few strings. I admit it's dirty but it was throwaway code for an isolated case. Edit: eh, guys, as I stated the string came from a binary dump. I didn't get to choose the encoding, it came from ROM in an embedded system with a different Endianness. I had to figure out a way to make it human readable.
    • justincormack 13y ago
      Use UTF8, no endian issues. Thats yet another reason why UTF16 and UTF32 are broken.
      • monkeyninja 13y ago
        language will not store unicode string internally with UTF8. Yes, we use it as input and output, but in memory, utf8 is terrible for random access characters. endian is only an issue (normally) for input and output, not really an issue for internal storage. especially when using UTF16 and UTF32 you know exactly the size of items.
        • jeltz 13y ago
          You cannot do random access at all in Unicode, not even UTF-32 (and absolutely not UTF-16), due to combining characters.
• deleted 13y ago
  [deleted]
• edent 13y ago
  ˙ƃuᴉuɐǝɯ ⅋ 'spɹoʍ 'sɥdʎlƃ 'sɹǝʇɔɐɹɐɥɔ uǝǝʍʇǝq 'ɹǝʌǝʍoɥ 'ǝɔuǝɹǝɟɟᴉp ɐ sᴉ ǝɹǝɥ┴ ˙ʇxǝʇ ɥʇᴉʍ punoɹɐ ƃuᴉsɹɐ oʇ sǝɯoɔ ʇᴉ uǝɥʍ sǝᴉʇᴉlᴉqᴉssod ƃuᴉʇsǝɹǝʇuᴉ ǝɯos sɹǝɟɟo ǝpoɔᴉu∩
  • antocv 13y ago
    Awesome way to exercise the brain.
    • afandian 13y ago
      Interesting. I had no problem reading that (except for 'arsing' which I thought I'd misread). The ability of the brain to pattern-match upside down is amazing.
      • ceras 13y ago
        Varies by person. I'm nearly 100% incapable of reading upside down text.
      • aroman 13y ago
        Fascinatingly, I read your comment first, then tried to read the upside down post — the only word I had trouble with was arsing. Sight reading is really fascinating.
  • vorg 13y ago
    Which looks cleaner, "丄" or "┴" ? I.e. "ǝɹǝɥ┴" or ǝɹǝɥ丄" ?
• cafard 13y ago
  Upvotes for the OP who posts "Disrupt 'Is Broken'".
• this_user 13y ago
  The string type isn't broken. If anything these "X is broken" posts are broken. Taking one special case, finding problems with that case and deducing that the whole concept must therefore be discarded is just silly. Strings work fine for the vast majority of use cases. No technology is free of flaws and engineering decisions are almost always based on weighting the pros and cons and choosing a solution that on balance works best. Strings are a useful feature and Unicode is a notoriously hard problem. Proposing to go back to arrays of characters makes things worse for most people in most cases and therefore is not a practical solution.
  • jckt 13y ago
    Exactly. Engineering =/= Maths.
  • mercurial 13y ago
    In my experience, the world is full of software which "work fine for the majority of use cases" until the point where you take the wrong code path and things go south.
    • jodrellblank 13y ago
      Much like human brains, and business processes.
  • lnanek2 13y ago
    That's OK, sounds like he is writing a new language, so screwing up on the strings implementation is par for the course. Languages and databases don't typically get correct string handling for many years later after they are born, if ever. Supporting all the unicode and other character set insanity takes years of work. Asking someone writing a language to get strings right is like asking a five year old to obtain a drivers license.
  • gutnor 13y ago
    Vast majority of use cases in the English-speaking world. In other countries like China, Japan, India, ... those edge cases are common enough to represent a significant portion of use cases and make X truly broken. The article is maybe a bit provocative, but you know what, that's exactly what is needed to raise awareness of mainly US-centric developers who would completely ignore the technical issues until they face a clone in China whose only innovative feature is not breaking on Chinese text.
• michaelfeathers 13y ago
  This is now my favorite example of a leaky abstraction.
• b-johansson 13y ago
  If you are actually manipulating strings rather than just storing and pushing them around I would suggest looking at ICU. Handling Unicode is difficult and it's easy to confuse encodings, code points and glyphs or make assumptions based on your own culture and language. ICU has support for a lot of the basic operations you would want to perform on strings as well as conversion to whatever format is suitable for your platform and environment.
• jbert 13y ago
  Perl seems to pass nearly all the tests (including uppercasing baffle): $ perl -E 'use utf8; binmode STDOUT, ":utf8"; say uc("baffle");' BAFFLE The only failure I can see is that it treats "no<combining diaresis>el" as 5 characters (so reports length as 5 and reversing places the accent on the wrong character). That's documented here: http://perldoc.perl.org/perluniintro.html#Handling-Unicode http://perldoc.perl.org/perluniintro.html#Handling-Unicode "Note that Perl considers grapheme clusters to be separate characters" All else seems to work though (including precomposed/decomoposed string equiality etc). The docco also says that perl's regex engine with Do The Right Thing with matching the entire grapheme cluster as a single char.
  • cursork 13y ago
    Perl is actually very good with Unicode. Note that a character is "The smallest component of written language that has semantic value" according to the Unicode glossary - I'd say Perl respects that meaning. As noted in the docs, graphemes can be handled with \X in regular expressions (although admittedly that's not pretty): my $length = 0; $length++ while $dec =~ /\X/g; Note that a grapheme is defined as "A minimally distinctive unit of writing in the context of a particular writing system" - i.e. context is required to determine what a grapheme actually is. A few others have pointed that out... Given the definitions from Unicode, Perl does a pretty good job (esp. when using Unicode::Normalize to normalize input). http://www.unicode.org/glossary/ http://www.unicode.org/glossary/
  • llimllib 13y ago
    Python 3 gets that one, but python 2.7 doesn't: $ python3 -c 'print("baffle".upper())' BAFFLE $ python -c 'print "baffle".upper()' BAfflE $ python -c 'print u"baffle".upper()' BAϬ„E
    • deathanatos 13y ago
      It's interesting that you get BAFFLE for the first one. I get the same result in both 3 and 2. Note first that the reason you get "BAϬ„E" is a bit of garbarge-in garbage-out. Strangely, the interpreter isn't rejecting that with the typical "SyntaxError: Non-ASCII character <char> in file" error; instead, it appears to be assuming ISO-8859-1, and then performing .upper(). You can fix that: python2 -c '# coding: utf-8 print u"baffle".upper()' (Note, of course, that the #coding needs to match your terminals encoding, which is likely UTF-8, but it isn't guaranteed.) That, for me, prints "BAfflE" in both Python 2 and 3 (adjusting for 3 by adding parens around print, and removing the u prefix on the literal.) I'm on Python 3.2, so perhaps 3.3 does better. (I'm behind on updates, but last I did update, Gentoo stable was still on 3.2.)
• monkeyninja 13y ago
  I don't understand the reason of using C++ char array to store unicode text....
• daGrevis 13y ago
  Logically equivalent doesn't mean equivalent for computers. While you can't define why reverse of “noël“ is “lëon“ by set of rules that computer can follow, computer just can't know.
  • sp332 13y ago
    That's why the article says, it's better to have a bare-bytes data structure, than a broken string type.
  • zokier 13y ago
    Umm. For that case you definitely can define a valid reversing algorithm. The key is using grapheme clusters as the indivisible base unit. Sure, there are probably some weird languages that will not reverse properly with such algorithm, but it would still be a significant improvement over the current situation.
• pilif 13y ago
  Python 3 gets so much of this right. It's one of the things I really loved about python 3 as it allows for correct string handling in most cases (see below). Note that this is only really true with Python 3.3 and later as in earlier versions stuff would start breaking for characters outside of the BMP (which is where JS is still stuck at, btw) unless you had a wide build which was using a lot of memory for strings (4 bytes per character) In general, internally using unicode and converting to and from bytes when doing i/o is the right way to go. But: Due to http://en.wikipedia.org/wiki/Han_unification http://en.wikipedia.org/wiki/Han_unification being locked into Unicode with a language might not be feasible for everybody - especially in Asian regions, Unicode isn't yet as widely spread and you still need to deal with regional encodings, mainly because even with the huge character set of Unicode, we still can't reliably write in every language. Ruby 1.9 and later helps here by having many, many string types (as many as it knows encodings), which can't be assigned to each other without conversion. This allows you to still have an internal character set for your application and doing encoding/decoding at i/o time, but you're not stuck with unicode if that's not feasible for your use-case. People hate this though because it seems to interfere with their otherwise perfectly fine workflow ("why can't I assign this "string" I got from a user to this string variable here??"), but it's actually preventing data corruption (once strings of multiple encodings are mixed up, it's often impossible to un-mix them, if they have the same characer width). I don't know how good the library support for the various Unicode encodings is in Ruby though. According to the article, there still is trouble with correctly doing case transformations and reversing them. Which brings me to another point: Some of the stuff you do with strings isn't just dependent on string encoding, but also locale. Uppercasing rules for example depend on locale, so you need to keep that into account too. And, of course, deal with cases when you don't know the locale the string was in (encoding is hard enough and most of the cases undetectable - but locales - next to impossible). I laugh at people who constantly tell me that this isn't hard and that "it's just strings".
  • exDM69 13y ago
    > Python 3 gets so much of this right. It's one of the things I really loved about python 3 as it allows for correct string handling in most cases (see below). One of the biggest things that I feel Python gets right with the string type is that strings are immutable. It makes a lot of things easier. It really makes sense to have a good string type for small strings, stored in unicode. Immutability makes everything simpler. The string type is not a good fit for handling large amounts of text. There are trade offs for efficiency that have to be made to create a handy string type. It really makes sense to have a separate "bytes" type or some kind of StringBuffer for doing big text operations.
• jszumski 13y ago
  Objective-C handles the "baffle" case just fine.
• rayiner 13y ago
  This is why the U.S. dominates the software world. Back when everyone was figuring out how to express their languages, we had the option to punt on complexity and just use ASCII.
  • Dewie 13y ago
    It seems rather that it is the other way around - the US dominated (and still does) the computer industry, and so ASCII, the English-centered character set, became the standard. ASCII is good enough (you might lose some accents on certain characters in certain words and such, but nothing much) for English but has no consideration for any other characters that might be used in other languages. If Turkey was the dominant country in IT, I don't see why they wouldn't do the same thing only for their own alphabet; include all the characters of their alphabet (latin alphabet plus a few more), plus some more common characters used in math etc.
    • frezik 13y ago
      The OP probably needed to clarify. English having a simple alphabet gave the US a leg up on personal computing compared to the KJC countries. It's only one contributing factor, though.
  • adamtj 13y ago
    ASCII doesn't make the U.S. special. ASCII is special because it's from the U.S. Lots of people speak languages that trivially fit in 8 bits with no real "figuring out" to do. Before Unicode, we all had our different codepages or encodings. Including the U.S. The U.S. is pretty central to computing. Because of that, and because ASCII only uses 7 bits, some other 8-bit cultures use it as a subset for their native 8-bit encodings. Even in the U.S, we use extensions to ASCII so we can represent text in languages that are close cousins to English. I doubt you actually use ASCII much. You've probably been using either ISO 8859-1 (aka Latin-1), which is a superset of ASCII, or Windows-1252, which is a superset of Latin-1. http://msdn.microsoft.com/en-us/library/cc194884.aspx http://msdn.microsoft.com/en-us/library/cc194884.aspx This mess of incompatible codepages and culture specific encodings is one of the main problems that Unicode was invented to solve. It also happens to help languages which need more than 8 bits.
• pilif 13y ago
  A nitpick from the article >This spells trouble for languages using UTF-16 encodings (Java, C#, JavaScript). if they were using UTF-16, this wouldn't be a problem as UTF-16 can be used to perfectly well encode code points outside of the BMP (at the cost of losing ability for O(1) access to specific code points of course. If you need to know what the n-th code point is, you have to scan the string until the n-th position). They are, however, using UCS-2 which can't. If you use a library that knows about UCS-2 to work on strings encoded in UTF-16, then you will get broken characters, your counts will be off and case transformations might fail. Most languages that claim Unicode support still only have UCS-2 libraries (Python 3 is a notable exception)
  • Renaud 13y ago
    Exactly, UTF-16 perfectly defines surrogate pairs for code points that do not fit into the 16 bit plane. A perfect implementation of UTF-16 should have no problem, unfortunately, most are broken when it comes to surrogate pairs. Many languages pre-date the introduction of UTF-16 and implemented 16 bit string encoding as UCS-2, and still do. Then there are oddities like VBA using UTF-16 internally, but converting all strings going through the Win32 API as 8-bit (relying on the current code page for character translation!)...
  • jeltz 13y ago
    > Most languages that claim Unicode support still only have UCS-2 libraries (Python 3 is a notable exception) Most non-JVM languages[1] actually use UTF-8 as the internal encoding so they should not suffer from this. Python 3 does not use UTF-16 either, it selects an encoding based on the contents of the string. http://www.python.org/dev/peps/pep-0393/ http://www.python.org/dev/peps/pep-0393/ 1. I think .NET too uses UCS-2 or UTF-16, but I am not a Windows developer.
    • pilif 13y ago
      .NET uses UCS-2 because the Windows API uses UCS-2 (so when you use Visual Studio out of the box, you will get UCS-2). ECMAScript (JS) uses UCS-2 because that's all there was when the spec was written. Other scripting languages I know for certain are - PHP doesn't care and treats strings as arrays of bytes. All the str functions operate on these byte arrays and thus happily destroy your strings if they are encoded as anything but the old 8-bit encodings. If you need to support utf-8, you have to use different library functions (mb_*) and a special syntax in their regex support (/u modifier). - Python < 3 treats strings as byte arrays or UCS-2 depending on whether you use the byte type or the Unicode type. As such, it has all the same issues as all other UCS-2 libraries - Ruby < 1.9 treats strings a byte arrays. There is some limited UTF-8 support, but it's in additional libraries. The internal API is treating strings as byte arrays. Ruby >= 1.9 lets you chose your internal encoding. Most people use utf-8, but you don't have to. - Perl I don't know enough about, but I hear it as an UTF-8 mode that is actually well-supported by the language itself and gets almost everything right. These are the more common scripting languages. Of the compiled languages, I know for certain about Go (utf-8; good library support), C (OS dependent, but the standard string API treats strings as byte arrays), C++ (dito) and Delphi (UCS-2 since 2010, byte arrays before that) I would say that there are so many exceptions to the UTF-8 rule that I wouldn't say "most" languages are using UTF-8.
• falsedan 13y ago
  Mostly this article says that most languages choose NFC for their default normalization form, and don't attempt to detect & convert strings to that form automatically.
• delinka 13y ago
  Now let's take the lower case of "BAFFLE" - should we get "baffle" or should the string class/function/wtfe attempt to recognize that a ligature can replace "ffl" and return to us "baffle"? More generally, should the string library ever attempt to replace letter with ligatures? Should this be yet another option? And as I type this, another issue manifests: the spelling correction can't even recognize baffle as a properly spelled word; it highlights the 'ba' and ignores the rest.
  • ygra 13y ago
    Uppercasing and lowercasing is inherently lossy. E.g. the German ß becomes SS when uppercased, yet there is no way to know whether SS should be lowercased to ss or ß again. That's a reason why those things should be used, if at all, only as display transformations. Same goes for ligatures, but even those actually shouldn't be applied automatically, depending on the language. E.g. in German ligatures cannot span syllables and few layout engines can detect that.
    • zokier 13y ago
      I feel like I should learn German only so that I would be able to comment on the ß issue every time a Unicode thread pops up. From my uninformed point of view it is not really clear if ß should really be handled as a separate character/grapheme, or just as a ligature in rendering phase and stored as 'ss'. Or even if current-day orthography should be held at such a sacrosanct position that it shouldn't be changed to save significant amount of collective effort.
      • TillE 13y ago
        > or just as a ligature in rendering phase and stored as 'ss'. Probably. > to save significant amount of collective effort I've seen this kind of suggestion a number of times on HN, and I find it highly amusing. When confronted with a difficult challenge in representing the world on a computer, apparently the answer is to instead change the world. OK, but then how are you going to handle hundreds of years of legacy texts?
• jheriko 13y ago
  this hits on one of my biggest problems with native android and ios development. the wcs/wchar functions are largely broken or unusable... it caused me a real headache from not knowing upfront. the idea of the string type is just fine though (or a character array) broken implementations don't invalidate it, they just invalidate the myth of '3rd party libraries must be good because hundreds of programmers worked on them for years' - which is exactly a myth. it doesn't just apply to strings but everything. (not brokeness, just that you shouldn't expect them to work beyond what you can measure, and certainly shouldn't expect that they are flawless or even good implementations)
• JulianMorrison 13y ago
  For Go: the for-range loop iterates 5 times, reversed (manually, using the resulting runes) is l̈eon, utf8.RuneCount is 5. The blog has just recently been talking about text normalization[1] via a library, but it isn't built into the core. [1] http://blog.golang.org/normalization http://blog.golang.org/normalization
• deleted 13y ago
  [deleted]
• mathias 13y ago
  The article briefly mentions JavaScript, which uses something similar to UTF-16/UCS-2: http://mathiasbynens.be/notes/javascript-encoding> http://mathiasbynens.be/notes/javascript-encoding> Here’s a slightly more in-depth blog post on the many issues this causes, and how to avoid them in JavaScript: http://mathiasbynens.be/notes/javascript-unicode http://mathiasbynens.be/notes/javascript-unicode Some of these problems are briefly mentioned in the above post, too.
• panzi 13y ago
  While JavaScript (in browsers) has no way to normalize precomposed/decomposed strings, it has standard methods to correctly compare them: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe... https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Collator https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe... E.g.: var decomp="noël"; var precomp="noël"; console.log(decomp.split("")); console.log(precomp.split("")); console.log(decomp.localeCompare(precomp)); Prints: ["n", "o", "e", "̈", "l"] ["n", "o", "ë", "l"] 0 Browser support for this varies, The Intl.Collator interface is currently only supported Chrome (maybe also in Opera? Idk). Note: In Chrome when comparing (e.g. sorting) a lot of strings String.prototype.localeCompare is much slower than using a pre-composed Intl.Collator instance (because internally localeCompare creates a new collator for each call). Using Intl.Collator rediced startup time of my http://greattuneplayer.jit.su/ http://greattuneplayer.jit.su/ immensely. node.js currently has no support for Intl.*. It probably will be a compile time option for 0.12.
• Aardwolf 13y ago
  So what do you propose? Not have a string type, and let everyone handle all these cases manually instead? That will not end well...
• Dewie 13y ago
  What do you guys think about String in Haskell, where it is a list of char? Should it have some other default implementation, or should it have been more, um, decoupled from its implementation (don't know the correct terminology)?
• klrr 13y ago
  I hope Haskell Prime solves this. In Haskell String is literally a list of characters. This causes some overhead and leads to bad performance. Of course we got Text and for binary data you can use ByteString, but it's a bit of pain compared to having a real string type by default.
• DannoHung 13y ago
  Is it possible that Unicode is actually a bunch of horseshit? If literally nobody gets the spec right, then maybe the spec is wrong.
  • gsg 13y ago
    Unfortunately, general purpose text is not a clean simple thing that you can model nicely. Unicode is a mess because the problem it tries to solve is messy. Even if you could somehow come up with something obviously better, getting any new standard adopted widely enough to be useful would be a formidable, if not insurmountable, challenge. It's less pain to keep using Unicode and try to deal with the worst of the damage.
• al2o3cr 13y ago
  If anybody hasn't seen it, Glitchr's twitter is a fantastic example of how bizarro things can get with "140 characters". https://twitter.com/glitchr_ https://twitter.com/glitchr_ Note: may freak out browsers with a flaky Unicode implementation. For instance, scrolling that stream on the iOS Twitter client can get very laggy.
• mbq 13y ago
  There is a one more issue -- the easier it is to manipulate strings in some language the greater chance that they will be used as an internal data structure for things that certainly aren't texts. And this almost always causes substantial performance loss and awful bugs that are either untraceable due to a dependence on subtle configuration details or form security holes. Or both.
• ademarre 13y ago
  I think a lot of programmers don't properly understand character encoding simply because their programming languages don't give them the proper treatment. We need more APIs that force developers to acknowledge character encodings, probably in the type system.
• AsymetricCom 13y ago
  Now, look over here! When I substitute this context with that, ka-pow! now it's an array of characters! Big deal. I don't understand what the point of this article is when it shows the shortcomings of half a dozen different string implementations in random languages. Yes, if you don't understand the language, then your assumptions about how it works may be wrong. Big surprise, that doesn't mean every string implementation needs to conform to your expectations...
  • kbenson 13y ago
    Unicode is a standard. It says how to act in these circumstances. Calling out incorrect unicode implementations is useful. You shouldn't have to worry about inconsistent behavior between different languages that purport to support unicode strings. That's the point of a standard.
    • AsymetricCom 13y ago
      So who is the authority about correct unicode implementations, exactly? And how to different languages with different use cases and power conform to such a standard? Why doesn't this authority extend over language implementations? Because they know what they are doing, and understand the domain, unlike the author of this article. Look, I'm all for open standards, but saying that standards are required to be adhered to at the programming language level is just ignorance of the real world. The point of a standard isn't to dictate how data is architectured internally, it's to facilitate interoperability of systems at their endpoints. If you want interoperability of programmers, than make your own conforming language and get programmers to adopt it the right way, by competing in the market of ideas. There is no idea here other than the writer's unjustified expectation that he should just know how every language handles Unicode because??? Because Unicode is a standard? No.. that doesn't make sense at all. Mixing contexts to make the point here means there is no ground for his argument to stand on.
      • kbenson 13y ago
        So who is the authority about correct unicode implementations, exactly? The Unicode Consortium[1] publishes standards. If a language advertises unicode support, I expect it to follow that standard. Look, I'm all for open standards, but saying that standards are required to be adhered to at the programming language level is just ignorance of the real world I'm not saying a language has to do anything, but if it's advertising support for a well defined feature, and does not deliver correctly on that, I will call them out on it, and support anyone else who does as well. Should we all just throw our hands up and say "Well, it's done now, no point in making a big deal of it?" I would rather apply pressure to get things fixed, or at least make it well known enough that future language designers give it the care and attention it's due. There is no idea here other than the writer's unjustified expectation that he should just know how every language handles Unicode because??? Because Unicode is a standard? No.. Are you under the impression that what the author is attempting is not well defined? The unicode standard has conformance clauses about how to interpret unicode strings[2]. That means that if a language advertises it has/supports unicode strings, and fails the tests we've just seen, it's not conformant with the unicode standard. That would make this useful because it's pointing out bugs. If a language does not advertise unicode support, but supports some unicode features, then this is useful because it's making sure people are aware of the limits of their language. All too often people refer to the native string implementation in their language as supporting unicode, when clearly there are problems. 1: http://www.unicode.org/ http://www.unicode.org/ 2: http://www.unicode.org/versions/Unicode6.2.0/ch03.pdf http://www.unicode.org/versions/Unicode6.2.0/ch03.pdf (see section 3.2)
• NkVczPkybiXICG 13y ago
  All of these examples work in Haskell's canonical text library, 'text'! It's the only language I know of that works.
  • FreeFull 13y ago
    The reversal of the decomposed noël doesn't produce the right result. Converting baffle to uppercase does do the right thing though, and the rest works as expected.
• brihat 13y ago
  This article is mostly written from a European language perspective. For Indian scripts, storing combining characters as a separate code points is the right thing to do. For example, कि (ki) is composed of क and ि When I'm writing this in an editor, say, I typed ku (कु) instead of ki (कि) and I press backspace, I indeed want to see क rather than deleting the whole "कि".
  • frenchy 13y ago
    Only some times I figure, because if you want to make the first letter green, you'd want that to apply to the whole कि.
• brihat 13y ago
  The author intentionally chooses decomposed form. Indeed all of them work with Python 3. Here: Python 3.3.2+ (default, Oct 9 2013, 14:50:09) [GCC 4.8.1] on linux Type "help", "copyright", "credits" or "license" for more information. >>> noel="noël" >>> noel[::-1] # reverse 'lëon' >>> noel[0:3] # first three characters 'noë' >>> len(noel) # length 4 The point is, defining what is a character based on how it is displayed is flawed. Just precompose the string ifg you want and carry on. Like I said in my other comment, making automatic conversion of decomposed -> precomposed wrecks havoc with Indian languages.
  • jfim 13y ago
    Works as expected too in Scala, although it might be because the terminal does normalization. scala> val noel = "Noël" noel: String = Noël scala> noel.reverse res0: String = lëoN scala> noel.take(3) res1: String = Noë scala> noel.length res2: Int = 4 scala> import java.text.Normalizer val nfdNoel = Normalizer.normalize(noel, Normalizer.Form.NFD) import java.text.Normalizer scala> nfdNoel: String = Noël scala> nfdNoel.length res3: Int = 5 scala> nfdNoel.reverse res4: String = l̈eoN scala> nfdNoel.take(3) res5: String = Noe The problem with an array of characters, as he mentions, is that it doesn't work properly in many use cases. If your array of characters stores 16 bit codepoints, it breaks with the 32 bit codepoints (Java got bit hard by that, where a char used to be a character prior to the introduction of surrogate pairs in Unicode); if it stores 32 bit codepoints, then it's pretty wasteful in most cases, which is exactly why you'd want a string type that handles storage of series of characters in an optimal fashion.
• deleted 13y ago
  [deleted]
  • alayne 13y ago
    Try the correct test input: noe\u0308l
    • deleted 13y ago
      [deleted]
• rverghes 13y ago
  Out of curiosity, why only have one string type? We don't do the same for numbers. Many languages don't have "number", they have int, float, long, etc. Instead of just String, maybe we should have ASCIIString, UTF8String, and UTF16String.
• gcr 13y ago
  For the record, Racket gets the "baffle" example right: racket@> (string-upcase "baffle") "BAFFLE" It also passes all of the author's other tests (except for the ones involving combining diacritics, but racket includes built-in functions for normalizing such strings so you can work with them)
• baddox 13y ago
  A big problem here is a lack of clear definitions for various concepts like "character," "reversed string," "upper case," etc. The author briefly recognizes this, but brushes it off with statements like "I generally expect that..." and "I assume most people would not be happy with the current result." I think these hand-wavings aren't helpful. Short of extensive surveying, which is bound to be controversial no matter what the result, talking about "general expectations" is a purely subjective notion, and not a good way to evaluate the actions of cold, soulless silicon that is just following orders. Like the author, I also consider myself a mostly reasonable person, yet is might come up with very different expectations. If I saw that "ffl" ligature, how would I know it's a ligature and not some single unrelated character in another language? You might respond "but it's clearly part of the word 'baffle' and should be capitalized thusly." But would you suggest that string libraries ship with word lists and perform contextual analysis to determine how to perform string operations? Surely that's a fool's errand, not to mention that it would inevitably produce unexpected results.
  • itsybitsycoder 13y ago
    "If I saw that "ffl" ligature, how would I know it's a ligature and not some single unrelated character in another language?" Because the name of that character is "Latin Small Ligature ffl". Knowing to capitalize ffl as FFL doesn't require a word list any more than knowing to capitalize "ffl" does.
• implicit 13y ago
  What we really should be doing is doing away with broken nomenclature. What does the "length" of a string even mean? A database will tell you it has to do with storage. A nontechnical person will say it's the number of symbols. A visual designer might say that it has to do with onscreen width when rasterized in a particular way. None of these people are obviously right or wrong. It's very useful to be able to count the number of glyphs in a string, or the number of unicode codepoints, or bytes, or pixels when rasterized in a particular way, but "length" isn't clear enough to unambiguously refer to any of them. Any meaning you try to ascribe to the "length" operation is going to be wrong to someone.
• revelation 13y ago
  I seem to have rather little use for the cases the author presents here. If I'm working with strings, they are either of the debug or internal variant, where even basic ASCII would suffice, or I get them from somewhere and don't touch them at all, just pass them around. But what I absolutely need in a language is to have a very very clear seperation between strings and byte arrays, or raw data, and ideally a way to transform between the two. C# gets this right with its byte and string types, the framework uses them correctly, and there is the wonderful Encoding namespace to interchange the two. Python 2.7 is the absolte worst, it's apparently impossible to get anything done with raw data and not run into some obscure 'ASCII codec can't handle octet 128' whatever exception (reminds you why we have strict typing: magic is fucking annoying).
• AndyKelley 13y ago
  I don't think the solution to this problem is to make our string classes more complicated. I think it's to make our languages and character sets less complicated. I can't believe that multiple codepoints being used to generate a single glyph made it into the Unicode spec. That breaks a bunch of extremely useful abstractions. I think it is reasonable to expect human languages to be made up of distinct glypths that do not interfere with each other. Any language that does not is too complicated to be worth supporting. Let it die.
• duncan_bayne 13y ago
  I'd have hoped Common Lisp would fare well here, but SBCL (1.1.11 on 64-bit Linux Mint 15) is pretty broken. My results: string: noël, reversed: l̈eon, first 3 chars: noe, length: 5 string: 😸😾, reversed: 😾😸, first 1 char: 😸, length: 2 string: baffle, upcase: BAfflE string: noël, equals precomposed: NIL Edited: GNU CLISP 2.49 produces identical results.
  • aerique 13y ago
    I was somewhat disappointed as well. I wrote some tests here: http://paste.lisp.org/display/140280 http://paste.lisp.org/display/140280 Perhaps playing around with different internal representations as pointed out by sedachv (https://news.ycombinator.com/item?id=6811407 https://news.ycombinator.com/item?id=6811407) would work but the initial, naive string usage doesn't work. While I expected the default usage to work correctly in Common Lisp.
• jeorgun 13y ago
  I think the specific case of ligatures isn't a failure in strings per se, but a failure in Unicode in that it includes them in the first place. What "fi".upper() (or whatever) should do is kind of ambiguous. The following doesn't really seem appropriate: "fi".upper().lower() #=> "fi" But obviously nor does "fi".upper() #=> "fi" In Turkish (which distinguishes between dotted and dotless 'i'), this issue exists already: "ı".upper().lower() #=> "i" This case couldn't (so far as I know) be fixed by any string library without breaking Unicode compatibility, so it seems slightly disingenuous to call it an issue with strings.
• jwmerrill 13y ago
  It looks like Factor passes all of these tests. Hat tip to Daniel Ehrenberg.
• ddebernardy 13y ago
  This is misinformation. OP's strings are just wrong... >> "\u0308" => "̈" >> "\u00eb" => "ë" >> "noe\u0308l" => "noël" >> "no\u00ebl" => "noël" His noël examples work just fine if you don't copy/paste the string he posts, and instead type them in like I just did. If anything, languages are reporting correct reverses and length, since he's really manipulating 5 characters rather than four.
  • enko 13y ago
    Congratulations, you've discovered unicode composition! 2.0.0p247 :045 > Unicode::compose("e\u0308").unpack('U').first.to_s(16) => "eb" 2.0.0p247 :046 > Unicode::compose("\u00eb").unpack('U').first.to_s(16) => "eb" 2.0.0p247 :047 > Unicode::decompose("e\u0308").unpack('U').first.to_s(16) => "65" 2.0.0p247 :048 > Unicode::decompose("\u00eb").unpack('U').first.to_s(16) => "65" I presume the ones you pasted in were changed by the browser. His examples are not wrong at all, indeed how can a string be "wrong"?
    • ddebernardy 13y ago
      His example is "wrong" in the sense that you cannot reasonably complain that "noe¨l" gets reversed to "l¨eon" and put the "¨" part on top of the "l" when it does — which seems entirely correct. Or for that matter, that the string's length is 5 when there are indeed 5 characters. As for being changed by the browser, the latter (or rather the OS) copied what there was, and the OS pasted it verbatim insofar as I can tell.
• wazoox 13y ago
  Tom Christiansen (of Perl fame) made a much, much thorough analysis of Unicode problems in his OSCON 2011 presentation: http://www.oscon.com/oscon2012/public/schedule/detail/24252 http://www.oscon.com/oscon2012/public/schedule/detail/24252 Here are the slides: http://training.perl.com/OSCON2011/gbu/gbu.pdf http://training.perl.com/OSCON2011/gbu/gbu.pdf The site seems down ATM, but Internet Archive has it: https://web.archive.org/web/20121224081332/http://98.245.80.27/tcpc/OSCON2011/gbu.html https://web.archive.org/web/20121224081332/http://98.245.80....
• vfclists 13y ago
  Honestly I think 'you' computer programmers love useless challenges too much. Why can't you adopt lessons from Q? If it isn't easy to get some languages working with Unicode properly then fix the languages and leave Unicode alone. Remove all the language characteristics that makes working with Unicode difficult. If Unicode will not go to the language then the language must go to Unicode, or opt out of the computer era, or die!! KISS!!