[zorkw4rg]

I'm not so sure other languages do that any better (nodejs doesn't even support non-unicode filenames at all for instance). Modern python does a pretty good job at supporting unicode, very far away from being a "Mess" that's just very much not true at all. People always like to hate on python but then other languages supposedly designed by actually capable people do mess up other stuff all the time. Look at how the great Haskell represents strings for instance and what a clusterfuck[1] that is.

[1] https://mmhaskell.com/blog/2017/5/15/untangling-haskells-str...

[masklinn]

Rust is probably one of the languages which does this crap best, and that's thanks to static typing and deciding to not decide:

1. it has proper, validated unicode strings (though the stdlib is not grapheme-aware so manipulating these strings is not ideal)

2. it has proper bytes, entirely separate from strings

3. it has "the OS layer is a giant pile of shit" OsString, because file paths might be random bag of bytes (UNIX) or random bags of 16-bit values (and possibly some other hare-brained scheme on other platforms but I don't believe rust supports other osstrings currently)

4. and it has nul-terminated bag o'bytes CString

For the latter two, conversion to a "proper" language string is explicitly known to be lossy, and the developer has to decide what to do in that case for their application.

[jcranmer]

> 1. it has proper, validated unicode strings (though the stdlib is not grapheme-aware so manipulating these strings is not ideal)

Grapheme clusters are overrated in their importance for processing. The list of times you want to iterate over grapheme clusters:

1. You want to figure out where to position the cursor when you hit left or right.

2. You want to reverse a string. (When was the last time you wanted to do that?)

The list of times when you want to iterate over Unicode codepoints:

1. When you're implementing collation, grapheme cluster searching, case modification, normalization, line breaking, word breaking, or any other Unicode algorithm.

2. When you're trying to break text into separate RFC 2047 encoded-words.

3. When you're trying to display the fonts for a Unicode string.

4. When you're trying to convert between charsets.

Cases where neither is appropriate:

1. When you want to break text to separate lines on the screen.

2. When you want to implement basic hashing/equality checks.

(I'm not sure where "cut the string down to 5 characters because we're out of display room" falls in this list. I suspect the actual answer is "wrong question, think about the problem differently").

Grapheme clusters is relatively expensive to compute, and its utility is very circumscribed. Iterating over Unicode codepoints is much more useful and foundational and yet still very cheap.

[zbentley]

> Grapheme clusters are overrated in their importance for processing. The list of times you want to iterate over grapheme clusters:

> 1. You want to figure out where to position the cursor when you hit left or right.

> 2. You want to reverse a string. (When was the last time you wanted to do that?)

You missed the big one:

3. You want to determine the logical (and often visual) length of a string.

Sure, there are some languages where logical-length is less meaningful as a concept, but there are many, many languages in which it's a useful concept, and can only be easily derived by iterating grapheme clusters.

[anonymfus]

Visual length of a string is measured in pixels and millimetres, not characters. In a font/graphics library, not in a text processing one.

[zbentley]

Sorry, visual length as in visual number of "character-equivalent for purposes of word length" things. Those things are close to, but not exactly the same as, grapheme clusters, so the latter can often be used as an imperfect (but much more useful than unicode points or bytes) proxy for the former.

There's no perfect representation of number-of-character-equivalents that doesn't require understanding of the language being handled (and it's meaningless in some languages as I said), but there are many written languages in which knowing the length in those terms is both extremely useful and extremely hard to do without grapheme cluster identification.

[Groxx]

>character-equivalent for purposes of word length

Serious question: why would you want to do this?

I know it's fashionable to limit usernames to X characters... but why? The main reason I've seen has been to limit the rendered length so there are some mostly-reliable UI patterns that don't need to worry about overflows or multiple lines. At least until someone names themselves:

Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ Ｗ

Which is 20 characters, no spaces, and will break loads of things.

(I'm intentionally ignoring "db column size" because that depends on your encoding, so it's unrelated to graphemes)

[masklinn]

So?

Rust's stdlib provides iteration on code units and code points. The use cases where these are useful are covered.

It does not provide iteration on grapheme clusters, the use cases where this is useful are not covered (and require an external dependency).

At no point am I requesting replacing codepoints-wise iteration by clusters-wise iteration.

[Manishearth]

I think a more accurate characterization is that neither code points nor grapheme clusters are usually what you want, but when you're naively processing text it's usually better to go with grapheme clusters so you don't mess up _as_ badly :)

There are definitely some operations that make sense on code points: but if you go through your list, (1), (2), (4) is something you'll rarely implement yourself (you just need a library), (3) is ... kinda rare? The most common valid use case for dealing with code points is parsing, where the grammar is defined in ascii or in terms of code points (which is relatively common).

Treating strings as either code points or graphemes basically enshrines the assumptions that segmentation operations make sense on strings at all -- they only do in specific contexts.

Most string operations you can think of come from incorrect assumptions about text. Like you said, the answer to most questions of the form "how do I X a string" is "wrong question" (reversing a string is my favorite example of this).

The only string operation that universally makes sense is concatenation (when dealing with "valid" strings, i.e. strings that actually make sense and don't do silly things like starting with a stray modifier character). Replacement makes some sense but you have to define "replacement" better based on your context. Taking substrings makes sense but typically only if you already have some metric of validity for the substring -- either that the substring was an ingredient of a prior concatenation, or that you have a defined text format like HTML that lets you parse out substrings. (This is why i actually kinda agree with Rust's decision to use bytes rather than code points for indexing strings -- if you're doing it right you should have obtained the offset from an operation on the string anyway, so it doesn't matter how you index it, so pick the fast one)

Most string operations go downhill from here where there's usually a right thing to do for that operation but it's highly context dependent.

Even hashing and equality are context-dependent, sometimes comparing bytes is enough, but other times you want to NFC or something and it gets messy quickly :)

In the midst of all this, grapheme clusters + NFC (what Swift does) are abstractions that let you naively deal with strings and mess up less. Your algorithm will still be wrong, but its incorrectness will cause fewer problems.

But yeah, you're absolutely right that grapheme clusters are pretty niche for when they're the correct tool to reach for. I'd just like to add that they're often the less blatantly incorrect tool to reach for :)

> (I'm not sure where "cut the string down to 5 characters because we're out of display room" falls in this list. I suspect the actual answer is "wrong question, think about the problem differently").

This is true, and not thinking about the problem differently is what caused the iOS Arabic text crash last year.

For many if not most scripts fewer code points is not a guarantee of shorter size -- you can even get this in Latin if you have a font with some wild kerning -- it's just that this is much easier to trigger in Arabic since you have some letters that have tiny medial forms but big final forms.

[tialaramex]

There's a very sound argument to be made for the opposite conclusion, that if we care about a problem we should make it necessary to solve the problem correctly or else stuff very obviously breaks, not have broken systems seem like they kinda work until they're used in anger.

Outside of MySQL (which unaccountably had a weird MySQL-only character encoding which only covered the BMP and named it "utf8" then when you tried to shove actual UTF-8 strings into it, they'd get silently truncated because YOLO MySQL) UTF-8 implementations tended to handle the other planes much better than UTF-16 implementations, many of which were in practice UCS-2 and then some thin excuses. Why? Because if you didn't handle multiple code units in UTF-8 nothing worked, you couldn't even write some English words like café properly. For years pretending your UCS-2 code was UTF-16 would only be noticed by people using obscure writing systems or academics.

I am also reminded of approaches to i18n for software primarily developed and tested mainly by monolingual English speakers. Obviously these users won't know if a localised variant they're examining is correctly translated, but they can be given a fake "locale" in which translated text is visibly different in some consistent way, e.g. it has been "flipped" upside down by abusing symbols that look kind of like the Latin alphabet upside down, or Pig Latin is used "Openway Ocumentday". The idea here again is that problems are obvious rather than corner cases, if the translations are broken or missing it'll say "Open Document" in the test locale which is "wrong" and you don't need to wait for a specialist German-speaking tester to point that out.

[Manishearth]

> There's a very sound argument to be made for the opposite conclusion, that if we care about a problem we should make it necessary to solve the problem correctly or else stuff very obviously breaks, not have broken systems seem like they kinda work until they're used in anger.

Oh, definitely :)

I'm rationalizing the focus on grapheme clusters, if I had my way "what is a string" would be a mandatory unit of programming language education and reasoning about this would be more strongly enforced by programming languages.

[CyberShadow]

> 1. it has proper, validated unicode strings (though the stdlib is not grapheme-aware so manipulating these strings is not ideal)

Sigh, I hoped newer languages would avoid D's mistake. Auto-decoding is slow, unnecessary in most cases, and still only gives you partial correctness, depending on what you're trying to do. It also means that even the simplest string operations may fail, which has consequences on the complexity of the API.

[masklinn]

I have no idea what you're talking about. Rust rarely does auto- anything, and certainly does not decode (or transcode) strings without an explicit request by the developer: Rust strings are not inherently iterable. As developer, you specifically request an iterable on code units or code points (or grapheme clusters or words through https://unicode-rs.github.io/unicode-segmentation)

[CyberShadow]

I see, thanks for the clarification - looks like I mis-extrapolated from your comment.

[nikic]

That sounds more like an implementation issue than a design issue. If you are using UTF-8 actual decoding into Unicode code points is not necessary for most operations and Rust will not do that.

It also does not imply that string operations may fail. String construction from raw bytes may fail, but otherwise the use of UTF-8 strings should not introduce additional failure conditions.

[CyberShadow]

> I'm not so sure other languages do that any better

I can only speak of D since I'm familiar with it.

In D, strings are arrays of chars. The standard library assumes that they contain valid UTF-8 code points and together form valid UTF-8, but it's ultimately your responsibility to ensure that. This assumption allows the standard library to present strings as ranges of Unicode code points (i.e. whole characters spanning multiple bytes).

To enforce this assumption, when raw data is interpreted as D strings it is usually checked if it's valid UTF-8. For example, readText() takes a filename, reads its contents, and checks that it is valid UTF-8 before returning it. assumeUTF() will take an array of bytes and return it as-is, but will throw in a check when the program is built in debug mode. Finally, string.representation (nothing more than a cast under the hood) gives you the raw bytes, and .byChar etc. allow iteration over code units rather than code points, if you really want to avoid auto-decoding and process a string byte-wise.

There are also types for UTF-16 and UTF-32 strings and code units, which work as the above. For other encodings, there's std.encoding which provides conversion to and from some common ones.

My only grip with how D deals with Unicode is that its standard library insists on decoding UTF-8 into code points when processing strings as ranges (and many string processing functions in other languages are written as generic range algorithms in D). Often enough, it's unnecessary, slow, and makes processing non-UTF text a chore, but it's not too hard to avoid. Other than this, I think D's approach to Unicode is better among the other languages I've seen.

[ChrisRackauckas]

Some other languages handle Unicode just fine. Rust and Julia are fine. IMO you need to build unicode understanding into string handling from the start for it to happen. Every function and detail needs to make UTF-8 sense, not just some some unicode handling library.

[marcosdumay]

Haskell get things much better than Python.

For example, if you use `readFile` from Data.Text, you'll use utf-8 names and read utf-8 content. If you use `readFile` from Data.ByteString, you'll use utf-8 names and read utf-8 content. You just import whatever you want at the local namespace and use it.

If you define a conversion procedure, you can make code that accepts either text or bytes, and return either one too, automatically. The tools for working with text have equivalents for working with bytes too, whenever that makes sense. Combining text with bytes is a type error, but there are so many shortcuts for going from one to the other that one barely notices them (unless you are concerned about performance, then you will notice).

That small article is basically all that you have to read to be productive dealing with text and bytes differences.

[joshuamorton]

Pretty much everything you've described is possible in Python. The open function can return bytes or utf8, depending on what you ask for, and converting between the two is simply a call to .decode or .encode.

Combing text with bytes is a type error.

There, you're ready for text in python3.

[ris]

This is one of the things that makes it hard for me to let go of Python, even though my programming style is evolving more towards functional languages: I've become very spoiled and take for granted a lot of the peripheral sanity and general well-behavedness that Python has, certainly in the unix environment.

Every other language or language implementation that I encounter seems to end up having an "oh god no" surprise or three hiding not-very-deep beneath the surface. Let's not even talk about ruby.

[hodgesrm]

Java is pretty good at character processing and has been since the inception of the language. Adopting Unicode from the start helped enormously, along with clearly separating String from byte[] in the type system. Finally the fact you have static typing makes it a lot easier to avoid 'what the heck do I have here' problems with byte vs. str that still pop up even in Python3.

That said Python3 is vastly better than Python2. Basic operations like reading/writing to files and serialization to JSON for the most part just work without having to worry about encodings or manipulate anything other than str objects. I'm sure there are lots of cases where that's not true but for my work at least string handling is no longer a major issue in writing correct programs. The defaults largely seem to work.

[ghusbands]

Java's string handling is also broken by default in a few ways, due to it historically using UCS-2 internally and hence still allowing surrogate pairs to get split up, giving broken unicode strings.

[hodgesrm]

I have not personally encountered this problem but it's definitely there. The other problem historically is that Java didn't explicitly require clients to specify encodings explicitly when moving between strings and bytes. That's been cleaned up quite a bit in recent releases of the JDK.

All things considered Java character handling was an enormous improvement over the languages that preceded it and still better than implementations in many other languages. (I wish the same could be said of date handling.)

[pvarangot]

What's the deal with Haskell strings? It's not a mess, it's basically enforcing the same "unicode sandwich" approach Python recommends by using the type checker. Of course to do that you need one type for when the string is in the different possible different layers of the sandwich.

There's added types for lazy vs. non-lazy but that's for performance optimization, and don't get me started on how Python "get messy" when you want to do performance optimization because it usually kicks you out of the language.

[bunderbunder]

> What's the deal with Haskell strings?

I think the linked article laid the case fairly well. Basically, Haskell has a bunch of string types you need to understand and fret about, and the one named "String" is the one you almost never want, but it's also the only one with decent ergonomics unless you know to install a compiler extension.

I think it's a fair criticism. The "Lots of different string types" thing isn't (IMO) such a big deal coming from a language of Haskell's vintage. Given what Python's "decade-plus spent with a giant breaking change right in the middle of the platform hanging over our heads" wild ride has been like, I can't blame anyone for not wanting to replicate the adventure.

But, for newcomers, the whole thing where you need to know to

  {-# LANGUAGE Support, Twenty, First, Century #-}

is a pretty big stumbling block.

[pvarangot]

I think that "deal" is just complains coming from someone that doesn't yet understand the engineering tradeoffs between strong static and weak type systems. That the nice functions for String come in the Prologue and that you need to implement or use other libraries for the functions for byte sequences or other stuff is not an excuse or a problem of the language as a tool.