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digitalmars.D - A grave Prayer

reply Georg Wrede <georg.wrede nospam.org> writes:
We've wasted truckloads of ink lately on the UTF issue.

Seems we're tangled in this like the new machine room boy who was later 
found dead. He got so wound up with cat-5 cables he got asphyxiated.


The prayer:

Please remove the *char*, *wchar* and *dchar* basic data types from the 
documentation!

Please remove ""c, ""w and ""d from the documentation!


The illusion they make is more than 70% responsible for the recent 
wasteage of ink here. Further, they will cloud the minds of any new D 
user -- without anybody even noticing.

For example, there is no such thing as an 8 bit utf char. It simply does 
not exist. The mere hint of such in the documentation has to be the 
result of a slipup of the mind.

---

There are other things to fix regarding strings, utf, and such, but it 
will take some time before we develop a collective understanding about 
them.

But the documentation should be changed RIGHT NOW, so as to not cause 
further misunderstanding among ourselves, and to not introduce this to 
all new readers.

Anybody who reads these archives a year from now, can't help feeling we 
are a bunch of pathological cases harboring an incredible psychosis -- 
about something that is basically trivial.

---

ps, this is not a rhetorical joke, I'm really asking for the removals.
Nov 23 2005
parent reply Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Georg Wrede wrote:
 We've wasted truckloads of ink lately on the UTF issue.
 
 Seems we're tangled in this like the new machine room boy who was later 
 found dead. He got so wound up with cat-5 cables he got asphyxiated.
 
 
 The prayer:
 
 Please remove the *char*, *wchar* and *dchar* basic data types from the 
 documentation!

What atleast should be changed is the suggestion that the C char is replacable by the D char, and a slight change in definition: char: UTF-8 code unit wchar: UTF-16 code unit dchar: UTF-32 code unit and/or unicode character
 
 Please remove ""c, ""w and ""d from the documentation!

So you suggest that users should use an explicit cast instead? /Oskar
Nov 23 2005
parent reply Georg Wrede <georg.wrede nospam.org> writes:
Oskar Linde wrote:
 Georg Wrede wrote:
 
 We've wasted truckloads of ink lately on the UTF issue.

 The prayer:

 Please remove the *char*, *wchar* and *dchar* basic data types from 
 the documentation!

What atleast should be changed is the suggestion that the C char is replacable by the D char, and a slight change in definition: char: UTF-8 code unit wchar: UTF-16 code unit dchar: UTF-32 code unit and/or unicode character

A UTF-8 code unit can not be stored in char. Therefore UTF can't be mentioned at all in this context. By the same token, and because of symmetry, the wchar and dchar things should vanish. Disappear. Get nuked. The language manual (as opposed to the Phobos docs), should not once use the word UTF anywhere. Except possibly stating that a conformant compiler has to accept source code files that are stored in UTF. --- If a programmer decides to do UTF mangling, then he should store the intermediate results in ubytes, ushorts and uints. This way he can avoid getting tangled and tripped up before or later. And this way he keeps remembering that it's on his responsibility to get things right.
 Please remove ""c, ""w and ""d from the documentation!

So you suggest that users should use an explicit cast instead?

No. How, or in what form the string literals get internally stored, is the compiler vendor's own private matter. And definitely not part of a language specification. The string literal decorations only create a huge amount of distraction, sending every programmer on a wild goose chase, possibly several times, before they either finds someone who explains things, or they switch away from D. Behind the scenes, a smart compiler manufacturer probably stores all string literals as UTF-8. Nice. Or as some other representation that's convenient for him, be it UTF-whatever, or even a native encoding. In any case, the compiler knows what this representation is. When the string gets used (gets assigned to a variable, or put in a structure, or printed to screen), then the compiler should implicitly cast (as in toUTFxxx and not the current "cast") the string to what's expected. We can have "string types", like [c/w/d]char[], but not standalone UTF chars. When the string literal gets assigned to any of these, then it should get converted. Actually, a smart compiler would already store the string literal in the width the string will get used, it's got the info right there in the same source file. And in case the programmer is real dumb and assigns the same literal to more than one UTF width, it could be stored in all of those separately. -- But the brain cells of the compiler writer should be put to more productive issues than this. Probably the easiest would be to just decide that UTF-8 is it. And use that while something else is not demanded. Or UTF-whatever else, depending on the platform. But the D programmer should never have to cast a string literal. The D programmer should not necessarily even know that representation. The only situation he would need to know it is if his program goes directly to the executable memory image snooping for the literal. I'm not sure that should be legal.
Nov 23 2005
next sibling parent reply "Regan Heath" <regan netwin.co.nz> writes:
On Wed, 23 Nov 2005 21:16:03 +0200, Georg Wrede <georg.wrede nospam.org>  
wrote:
 Oskar Linde wrote:
 Georg Wrede wrote:

 We've wasted truckloads of ink lately on the UTF issue.

 The prayer:

 Please remove the *char*, *wchar* and *dchar* basic data types from  
 the documentation!

replacable by the D char, and a slight change in definition: char: UTF-8 code unit wchar: UTF-16 code unit dchar: UTF-32 code unit and/or unicode character

A UTF-8 code unit can not be stored in char. Therefore UTF can't be mentioned at all in this context.

I suspect we're having terminology issues again. http://en.wikipedia.org/wiki/Unicode "each code point may be represented by a variable number of code values." "code point" == "character" "code value" == part of a (or in some cases a complete) character I think Oscar's is correct (because I believe "code unit" == "code value") and char does contain a UTF-8 code value/unit. However, Georg is also correct (because I suspect he meant) that a char can not contain all Unicode(*) code points. It can contain some, those with values less than 255 but not others. (*) Note I did not say UTF-8 here, I believe it's incorrect to do so. code points are universal across all the UTF encodings, they are simply represented by different code values/units depending on the encoding used. Regan
Nov 23 2005
next sibling parent Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Regan Heath wrote:
 On Wed, 23 Nov 2005 21:16:03 +0200, Georg Wrede 
 <georg.wrede nospam.org>  wrote:
 
 Oskar Linde wrote:

 Georg Wrede wrote:

 We've wasted truckloads of ink lately on the UTF issue.

 The prayer:

 Please remove the *char*, *wchar* and *dchar* basic data types from  
 the documentation!

What atleast should be changed is the suggestion that the C char is replacable by the D char, and a slight change in definition: char: UTF-8 code unit wchar: UTF-16 code unit dchar: UTF-32 code unit and/or unicode character

A UTF-8 code unit can not be stored in char. Therefore UTF can't be mentioned at all in this context.

I suspect we're having terminology issues again. http://en.wikipedia.org/wiki/Unicode "each code point may be represented by a variable number of code values." "code point" == "character" "code value" == part of a (or in some cases a complete) character I think Oscar's is correct (because I believe "code unit" == "code value") and char does contain a UTF-8 code value/unit. However, Georg is also correct (because I suspect he meant) that a char can not contain all Unicode(*) code points. It can contain some, those with values less than 255 but not others.

I think you are correct in your analysis Regan. I was actually referring to your definitions in: news://news.digitalmars.com:119/ops0bhkaaa23k2f5 nrage.netwin.co.nz digitalmars.D/30029 and trying to be very careful to use the agreed terminology: character: (Unicode character/symbol) code unit: (part of the actual encoding) I feel that I may have been a bit dense in my second reply to Georg. Apologies. Regards, Oskar
Nov 23 2005
prev sibling next sibling parent reply Bruno Medeiros <daiphoenixNO SPAMlycos.com> writes:
Regan Heath wrote:
 On Wed, 23 Nov 2005 21:16:03 +0200, Georg Wrede 
 <georg.wrede nospam.org>  wrote:
 
 Oskar Linde wrote:

 Georg Wrede wrote:

 We've wasted truckloads of ink lately on the UTF issue.

 The prayer:

 Please remove the *char*, *wchar* and *dchar* basic data types from  
 the documentation!

What atleast should be changed is the suggestion that the C char is replacable by the D char, and a slight change in definition: char: UTF-8 code unit wchar: UTF-16 code unit dchar: UTF-32 code unit and/or unicode character

A UTF-8 code unit can not be stored in char. Therefore UTF can't be mentioned at all in this context.

I suspect we're having terminology issues again. http://en.wikipedia.org/wiki/Unicode "each code point may be represented by a variable number of code values." "code point" == "character" "code value" == part of a (or in some cases a complete) character I think Oscar's is correct (because I believe "code unit" == "code value") and char does contain a UTF-8 code value/unit.

 However, Georg is also correct (because I suspect he meant) that a char  
 can not contain all Unicode(*) code points. It can contain some, those  
 with values less than 255 but not others.

takes two bytes of storage. "A character whose code point is below U+0080 is encoded with a single byte that contains its code point: these correspond exactly to the 128 characters of 7-bit ASCII." http://en.wikipedia.org/wiki/UTF-8 "a) Use UTF-8. This preserves ASCII, but not Latin-1, because the characters >127 are different from Latin-1. UTF-8 uses the bytes in the ASCII only for ASCII characters. " http://www.unicode.org/faq/utf_bom.html I've actually only found this today when trying to writefln(''); -- Bruno Medeiros - CS/E student "Certain aspects of D are a pathway to many abilities some consider to be... unnatural."
Nov 23 2005
next sibling parent "Regan Heath" <regan netwin.co.nz> writes:
On Wed, 23 Nov 2005 20:50:16 +0000, Bruno Medeiros  
<daiphoenixNO SPAMlycos.com> wrote:
 Regan Heath wrote:
 However, Georg is also correct (because I suspect he meant) that a  
 char  can not contain all Unicode(*) code points. It can contain some,  
 those  with values less than 255 but not others.

Wrong actually, it can only contain codepoints below 128. Above that it takes two bytes of storage.

Thanks for the correction. I wasn't really sure. Regan
Nov 23 2005
prev sibling parent reply =?UTF-8?B?SmFyaS1NYXR0aSBNw6RrZWzDpA==?= <jmjmak invalid_utu.fi> writes:
Bruno Medeiros wrote:
 "a) Use UTF-8. This preserves ASCII, but not Latin-1, because the 
 characters >127 are different from Latin-1. UTF-8 uses the bytes in the 
 ASCII only for ASCII characters. "
 http://www.unicode.org/faq/utf_bom.html
 
 I've actually only found this today when trying to writefln('ç');

That's odd. I tried this on Linux (dmd .139): writefln('ༀ'); // -> no error! char a = 'ༀ'; // -> error! It seems that DMD allows all Unicode-character values as character literals (IMO this is correct behavior). One problem is that while you cannot assign the om-symbol 'ༀ' to a char (this is also correct - 3840>127), you can do this: char a = 'ä'; // -> no error! writefln(a); // outputs: Error: 4invalid UTF-8 sequence (oops!)
Nov 23 2005
parent reply Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Jari-Matti Mäkelä wrote:
 Bruno Medeiros wrote:
 
 "a) Use UTF-8. This preserves ASCII, but not Latin-1, because the 
 characters >127 are different from Latin-1. UTF-8 uses the bytes in 
 the ASCII only for ASCII characters. "
 http://www.unicode.org/faq/utf_bom.html

 I've actually only found this today when trying to writefln('ç');

That's odd. I tried this on Linux (dmd .139): writefln('ༀ'); // -> no error! char a = 'ༀ'; // -> error! It seems that DMD allows all Unicode-character values as character literals (IMO this is correct behavior). One problem is that while you cannot assign the om-symbol 'ༀ' to a char (this is also correct - 3840>127), you can do this: char a = 'ä'; // -> no error! writefln(a); // outputs: Error: 4invalid UTF-8 sequence (oops!)

I think Bruno may have been using a non-unicode format like Latin-1 for his sources. 'ç' would then appear as garbage to the compiler. /Oskar
Nov 23 2005
parent reply =?UTF-8?B?SmFyaS1NYXR0aSBNw6RrZWzDpA==?= <jmjmak invalid_utu.fi> writes:
Oskar Linde wrote:
 Jari-Matti Mäkelä wrote:
 
 Bruno Medeiros wrote:

 "a) Use UTF-8. This preserves ASCII, but not Latin-1, because the 
 characters >127 are different from Latin-1. UTF-8 uses the bytes in 
 the ASCII only for ASCII characters. "
 http://www.unicode.org/faq/utf_bom.html

 I've actually only found this today when trying to writefln('ç');

That's odd. I tried this on Linux (dmd .139): writefln('ༀ'); // -> no error! char a = 'ༀ'; // -> error! It seems that DMD allows all Unicode-character values as character literals (IMO this is correct behavior). One problem is that while you cannot assign the om-symbol 'ༀ' to a char (this is also correct - 3840>127), you can do this: char a = 'ä'; // -> no error! writefln(a); // outputs: Error: 4invalid UTF-8 sequence (oops!)

I think Bruno may have been using a non-unicode format like Latin-1 for his sources. 'ç' would then appear as garbage to the compiler.

Yes, that might be true if he's using Windows. On Linux the compiler input must be valid Unicode. Maybe it's hard to create Unicode-compliant programs on Windows since even Sun Java has some problems with Unicode class names on Windows XP. -- My point here was that since char[] is a fully valid UTF-8 string and the index/slice-operators are intelligent enough to work on the Unicode-symbol level [code 1], we should be able to store Unicode symbols to a char-variable as well. You see, an UTF-8 symbol requires 8-32 bits of storage space, so it would be perfectly possible to implement an UTF-8 symbol (char) using standard 32-bit integers or 1-4 x 8-bit bytes. The current implementation seems to be always using 1 x 8-bit byte for the char-type and n x 8-bit bytes for char[] - strings. The strings work well but it's impossible to store a single UTF-8 character now. [code 1]: char[] a = "∇∆∈∋"; writefln(a[2]); //outputs: ∈ (a stupid implementation would output 0x87)
Nov 23 2005
next sibling parent Carlos Santander <csantander619 gmail.com> writes:
Jari-Matti Mäkelä escribió:
 
 Yes, that might be true if he's using Windows. On Linux the compiler 
 input must be valid Unicode. Maybe it's hard to create Unicode-compliant 

The compiler input must also be valid Unicode on Windows. Just try to feed it with some invalid characters and you'll see how it'll complain.
 programs on Windows since even Sun Java has some problems with Unicode 
 class names on Windows XP.
 
 -- 
 
 My point here was that since char[] is a fully valid UTF-8 string and 
 the index/slice-operators are intelligent enough to work on the 
 Unicode-symbol level [code 1], we should be able to store Unicode 
 symbols to a char-variable as well. You see, an UTF-8 symbol requires 
 8-32 bits of storage space, so it would be perfectly possible to 
 implement an UTF-8 symbol (char) using standard 32-bit integers or 1-4 x 
 8-bit bytes.
 
 The current implementation seems to be always using 1 x 8-bit byte for 
 the char-type and n x 8-bit bytes for char[] - strings. The strings work 
 well but it's impossible to store a single UTF-8 character now.
 
 [code 1]:
 
   char[] a = "∇∆∈∋";
   writefln(a[2]);  //outputs: ∈ (a stupid implementation would output 0x87)

-- Carlos Santander Bernal
Nov 23 2005
prev sibling parent reply Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Jari-Matti Mäkelä wrote:
 
 My point here was that since char[] is a fully valid UTF-8 string and 
 the index/slice-operators are intelligent enough to work on the 
 Unicode-symbol level [code 1], we should be able to store Unicode 
 symbols to a char-variable as well. 

No this is wrong. The index/slice operations have no idea about Unicode/UTF.
 You see, an UTF-8 symbol requires 
 8-32 bits of storage space, so it would be perfectly possible to 
 implement an UTF-8 symbol (char) using standard 32-bit integers or 1-4 x 
 8-bit bytes.
 
 The current implementation seems to be always using 1 x 8-bit byte for 
 the char-type and n x 8-bit bytes for char[] - strings. The strings work 
 well but it's impossible to store a single UTF-8 character now.

There is no such thing as a "UTF-8 character" or "UTF-8 symbol"... "Unicode character" or "UTF-8 code unit" UTF is merely the encoding. Unicode is the character set.
 [code 1]:
 
   char[] a = "∇∆∈∋";
   writefln(a[2]);  //outputs: ∈ (a stupid implementation would output 0x87)

You really had me confused there for a moment (I had to test this). Fortunately you are wrong. On what platform with what source code encoding have you tested this? The following is on DMD 0.139 linux: import std.stdio; void main() { char[] a = "åäö"; writef(a[1]); } Will print Error: 4invalid UTF-8 sequence Which is correct. (The error message might be slightly confusing though) import std.stdio; void main() { char[] a = "åäö"; writef(a[2..4]); } will print "ä" Which is correct. /Oskar
Nov 23 2005
next sibling parent reply =?UTF-8?B?SmFyaS1NYXR0aSBNw6RrZWzDpA==?= <jmjmak invalid_utu.fi> writes:
Oskar Linde wrote:
 Jari-Matti Mäkelä wrote:
 
 My point here was that since char[] is a fully valid UTF-8 string and 
 the index/slice-operators are intelligent enough to work on the 
 Unicode-symbol level [code 1], we should be able to store Unicode 
 symbols to a char-variable as well. 

No this is wrong. The index/slice operations have no idea about Unicode/UTF.

Unicode-aware. Anyway, these operations and a the char-type should know about Unicode.
 You see, an UTF-8 symbol requires 8-32 bits of storage space, so it 
 would be perfectly possible to implement an UTF-8 symbol (char) using 
 standard 32-bit integers or 1-4 x 8-bit bytes.

 The current implementation seems to be always using 1 x 8-bit byte for 
 the char-type and n x 8-bit bytes for char[] - strings. The strings 
 work well but it's impossible to store a single UTF-8 character now.

There is no such thing as a "UTF-8 character" or "UTF-8 symbol"... "Unicode character" or "UTF-8 code unit"

Ok, "UTF-8 symbol" -> "the UTF-8 encoded bytestream of an Unicode symbol"
 [code 1]:

   char[] a = "∇∆∈∋";
   writefln(a[2]);  //outputs: ∈ (a stupid implementation would output 
 0x87)

You really had me confused there for a moment (I had to test this). Fortunately you are wrong. On what platform with what source code encoding have you tested this? The following is on DMD 0.139 linux:

Sorry again, didn't test this. This ought to work, but it doesn't.
 import std.stdio;
 
 void main() {
   char[] a = "åäö";
   writef(a[2..4]);
 }
 
 will print "ä"
 Which is correct.

Actually it isn't correct behavior. There's no real need to change the string on a byte-level. Think now, you don't have to change individual bits on a ASCII-string either. In 7-bit ASCII the base unit is a 7-bit byte, in ISO-8859-x it is a 8-bit byte and in UTF-8 it is 8-32 bits. The smallest unit you need is the base unit.
Nov 24 2005
parent Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Jari-Matti Mäkelä wrote:
 Oskar Linde wrote:
 
 There is no such thing as a "UTF-8 character" or "UTF-8 symbol"... 
 "Unicode character" or "UTF-8 code unit"

Ok, "UTF-8 symbol" -> "the UTF-8 encoded bytestream of an Unicode symbol"

According to terminology, it is "UTF-8 code unit" or "UTF-8 code value".
 [code 1]:

   char[] a = "∇∆∈∋";
   writefln(a[2]);  //outputs: ∈ (a stupid implementation would output 
 0x87)

You really had me confused there for a moment (I had to test this). Fortunately you are wrong. On what platform with what source code encoding have you tested this? The following is on DMD 0.139 linux:

Sorry again, didn't test this. This ought to work, but it doesn't.
 import std.stdio;

 void main() {
   char[] a = "åäö";
   writef(a[2..4]);
 }

 will print "ä"
 Which is correct.

Actually it isn't correct behavior. There's no real need to change the string on a byte-level. Think now, you don't have to change individual bits on a ASCII-string either. In 7-bit ASCII the base unit is a 7-bit byte, in ISO-8859-x it is a 8-bit byte and in UTF-8 it is 8-32 bits. The smallest unit you need is the base unit.

Its rather a matter of efficiency. Character indexing on a utf-8 array is O(n) (You can of course make it better, but with more complexity and higher memory requirements), while code unit indexing is O(1). You actually very seldom need character indexing. Almost everything can be done on a code unit level. /Oskar
Nov 24 2005
prev sibling parent reply Georg Wrede <georg.wrede nospam.org> writes:
Oskar Linde wrote:
 
 void main() {
   char[] a = "åäö";
   writef(a[2..4]);
 }
 
 will print "ä"
 Which is correct.

Hmmmmmmmmm. "Correct" is currently under intense debate here.
Nov 24 2005
parent reply =?UTF-8?B?SmFyaS1NYXR0aSBNw6RrZWzDpA==?= <jmjmak invalid_utu.fi> writes:
Georg Wrede wrote:
 Oskar Linde wrote:
 
 void main() {
   char[] a = "åäö";
   writef(a[2..4]);
 }

 will print "ä"
 Which is correct.

Hmmmmmmmmm. "Correct" is currently under intense debate here.

Yes, the biggest problem here is that some people don't like the O(n) complexity of the 'correct' UTF-8 indexing. I'm not a string handling expert but I don't like the current implementation: char[] a = "åäö"; writefln(a.length); // outputs: 6 char[] a = "tässä tekstiä"; std.string.insert(a, 6, "vähän"); writefln(a); // outputs: tässä tekstiä
Nov 24 2005
parent Georg Wrede <georg.wrede nospam.org> writes:
Jari-Matti Mäkelä wrote:
 Yes, the biggest problem here is that some people don't like the O(n) 
 complexity of the 'correct' UTF-8 indexing.

Of course O(n) is worse than O(k). Then again, that may not be such a problem with actual applications, since the total time used to this usually is (almost) negligible compared to the total runtime activity of the application. And, if beta testing shows that the program is not "fast enough" with production data, then it is easy to profile a D program. If it turns out that precisely this causes the slowness, then one might use, say, UTF16 in those situations. No biggie. Or UTF32. It's actually a shame that we haven't tried all of this stuff already. The wc.d example might be a good candidate to try the three UTF encodings and time the results. And other examples would be quite easy to write. (Ha, a chance for newbies to become "D gurus": publish your results here!)
Nov 24 2005
prev sibling parent reply Georg Wrede <georg.wrede nospam.org> writes:
Regan Heath wrote:
 On Wed, 23 Nov 2005 21:16:03 +0200, Georg Wrede 
 <georg.wrede nospam.org>  wrote:
 
 A UTF-8 code unit can not be stored in char. Therefore UTF can't be  
 mentioned at all in this context.

I suspect we're having terminology issues again. Regan

Thanks! Of course! So "A UTF-8 code point".
Nov 23 2005
parent reply Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Georg Wrede wrote:
 Regan Heath wrote:
 
 On Wed, 23 Nov 2005 21:16:03 +0200, Georg Wrede 
 <georg.wrede nospam.org>  wrote:

 A UTF-8 code unit can not be stored in char. Therefore UTF can't be  
 mentioned at all in this context.

I suspect we're having terminology issues again. Regan

Thanks! Of course! So "A UTF-8 code point".

No... Apparently code point is a point in the unicode space. I.e. a character. The guys that came up with that should be shot though. ;) http://www.unicode.org/glossary/ There are no UTF-8 code points by terminology. Only UTF-8 code unit == UTF-8 code value Unicode code point == Unicode character == Unicode symbol :) /Oskar
Nov 23 2005
parent Georg Wrede <georg.wrede nospam.org> writes:
Oskar Linde wrote:
 Georg Wrede wrote:
 
 Regan Heath wrote:

 On Wed, 23 Nov 2005 21:16:03 +0200, Georg Wrede 
 <georg.wrede nospam.org>  wrote:

 A UTF-8 code unit can not be stored in char. Therefore UTF can't be  
 mentioned at all in this context.

I suspect we're having terminology issues again. Regan

Thanks! Of course! So "A UTF-8 code point".

No... Apparently code point is a point in the unicode space. I.e. a character. The guys that came up with that should be shot though. ;) http://www.unicode.org/glossary/ There are no UTF-8 code points by terminology. Only UTF-8 code unit == UTF-8 code value Unicode code point == Unicode character == Unicode symbol :) /Oskar

Aaaarrrghhhhh! :-P
Nov 23 2005
prev sibling parent reply Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Georg Wrede wrote:
 Oskar Linde wrote:
 
 Georg Wrede wrote:

 We've wasted truckloads of ink lately on the UTF issue.

 The prayer:

 Please remove the *char*, *wchar* and *dchar* basic data types from 
 the documentation!

What atleast should be changed is the suggestion that the C char is replacable by the D char, and a slight change in definition: char: UTF-8 code unit wchar: UTF-16 code unit dchar: UTF-32 code unit and/or unicode character

A UTF-8 code unit can not be stored in char. [...]

Can it not? I thought I had been doing this all the time... Why? (I know most Unicode code points aka characters can not be stored in a char)
 [...] Therefore UTF can't be
 mentioned at all in this context.

 By the same token, and because of symmetry, the wchar and dchar things 
 should vanish. Disappear. Get nuked.

A dchar can represent any Unicode character. Is that not enough reason to keep it?
 The language manual (as opposed to the Phobos docs), should not once use 
 the word UTF anywhere. Except possibly stating that a conformant 
 compiler has to accept source code files that are stored in UTF.

Why? It is often important to know the encoding of a string. (When dealing with system calls, c-library calls etc.) Doesn't D do the right thing to define Unicode as the character set and UTF-* as the supported encodings?
 
 ---
 
 If a programmer decides to do UTF mangling, then he should store the 
 intermediate results in ubytes, ushorts and uints. This way he can avoid 
 getting tangled and tripped up before or later.

Those are more or less equivalent to char, wchar, dchar. The difference is more a matter of convention. (and string/character literal handling) Doesn't the confusion rather lie in the name? (char may imply character rather than code unit. I agree that this is unfortunate.)
 And this way he keeps remembering that it's on his responsibility to get 
 things right.
 
 Please remove ""c, ""w and ""d from the documentation!

So you suggest that users should use an explicit cast instead?

No.

I think this may have been the reason for the implementation of the suffixes: print(char[] x) { printf("1\n"); } print(wchar[] x) { printf("2\n"); } void main() { print("hello"); } A remedy is very close to the current implementation. The following change in behaviour: string literals are always char[], but may be implicitly cast to wchar[] and dchar[]. print(char[] x) would therefore be a closer match. (All casts of literals are of course done at compile time.) Currently in D: string literals are __uncommitted char[] and may be implicitly cast to char[], wchar[] and dchar[]. No cast takes preference. D may be too agnostic about preferred encoding...
 How, or in what form the string literals get internally stored, is the 
 compiler vendor's own private matter. And definitely not part of a 
 language specification.

The form string literals are stored in affects the performance in many cases. Why remove this control from the programmer? Rereading your post, tryig to understand what you ask for leads me to assume that by your suggestion, a poor, but conforming, compiler may include a hidden call to a conversion function and a hidden memory allocation in this function call: foo("hello");
 The string literal decorations only create a huge amount of distraction, 
 sending every programmer on a wild goose chase, possibly several times, 
 before they either finds someone who explains things, or they switch 
 away from D.

I can not understand this confusion. It is currently very well specified how a character literal gets stored (and you get to pick between 3 different encodings). The problem lies in the "" form, where you have not specified the encoding. The compiler will try to infer the encoding depending on context. This is a weakness i think should be fixed by: - "" is char[], but may be implicitly cast to dchar[] and wchar[]
 Behind the scenes, a smart compiler manufacturer probably stores all 
 string literals as UTF-8. Nice. Or as some other representation that's 
 convenient for him, be it UTF-whatever, or even a native encoding. In 
 any case, the compiler knows what this representation is.
 
 When the string gets used (gets assigned to a variable, or put in a 
 structure, or printed to screen), then the compiler should implicitly 
 cast (as in toUTFxxx and not the current "cast") the string to what's 
 expected.

I start to understand you now... (first time reading)
 We can have "string types", like [c/w/d]char[], but not standalone UTF 
 chars. When the string literal gets assigned to any of these, then it 
 should get converted.
 
 Actually, a smart compiler would already store the string literal in the 
 width the string will get used, it's got the info right there in the 
 same source file. [...]

But this is exactly what D does! Only in a well defined way. Not by hiding it as an implementation detail.
 [...] And in case the programmer is real dumb and assigns 
 the same literal to more than one UTF width, it could be stored in all 
 of those separately. -- But the brain cells of the compiler writer 
 should be put to more productive issues than this.

How do you assign _one_ literal to more than one variable?
 The D programmer should not necessarily even know that representation. 
 The only situation he would need to know it is if his program goes 
 directly to the executable memory image snooping for the literal. I'm 
 not sure that should be legal.

What is the wrong with a well defined representation? Regards, /Oskar
Nov 23 2005
next sibling parent reply "Kris" <fu bar.com> writes:
"Oskar Linde" <oskar.lindeREM OVEgmail.com> wrote
[snip]
 A remedy is very close to the current implementation. The following change 
 in behaviour: string literals are always char[], but may be implicitly 
 cast to wchar[] and dchar[]. print(char[] x) would therefore be a closer 
 match.
 (All casts of literals are of course done at compile time.)

 Currently in D: string literals are __uncommitted char[] and may be 
 implicitly cast to char[], wchar[] and dchar[]. No cast takes preference.

Yes, very close. Rather than be uncommited they should default to char[]. A suffix can be used to direct as appropriate. This makes the behaviour more consistent in two (known) ways. There's the additional question as to whether the literal content should be used to imply the type (like literal chars and numerics do), but that's a different topic and probably not as important.
Nov 23 2005
parent reply Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Kris wrote:

 There's the additional question as to whether the literal content should be 
 used to imply the type (like literal chars and numerics do), but that's a 
 different topic and probably not as important. 

How would the content imply the type? All Unicode strings are representable equally by char[], wchar[] and dchar[]. Do you mean that the most optimal (memory wise) encoding is used? Or do you mean that file encoding could imply type? (This means that transcoding the source code could change program behaviour.) Char literals and numerals imply type because of limited representability. This is not the case with strings. /Oskar
Nov 23 2005
parent reply "Kris" <fu bar.com> writes:
"Oskar Linde" <oskar.lindeREM OVEgmail.com> wrote
 Kris wrote:

 There's the additional question as to whether the literal content should 
 be used to imply the type (like literal chars and numerics do), but 
 that's a different topic and probably not as important.

How would the content imply the type? All Unicode strings are representable equally by char[], wchar[] and dchar[]. Do you mean that the most optimal (memory wise) encoding is used? Or do you mean that file encoding could imply type? (This means that transcoding the source code could change program behaviour.)

I meant in terms of implying the "default" type. We're suggesting that default be char[], but if the literal contained unicode chars then the default might be something else. This is the method used to assign type to a char literal, but Walter has noted it might be confusing to do something similar with string literals. As indicated, I don't think this aspect is of much importance compared to the issues associated with an uncommited literal type ~ that uncommited aspect needs to be fixed, IMO.
Nov 23 2005
parent reply "Regan Heath" <regan netwin.co.nz> writes:
On Wed, 23 Nov 2005 13:18:49 -0800, Kris <fu bar.com> wrote:
 "Oskar Linde" <oskar.lindeREM OVEgmail.com> wrote
 Kris wrote:

 There's the additional question as to whether the literal content  
 should
 be used to imply the type (like literal chars and numerics do), but
 that's a different topic and probably not as important.

How would the content imply the type? All Unicode strings are representable equally by char[], wchar[] and dchar[]. Do you mean that the most optimal (memory wise) encoding is used? Or do you mean that file encoding could imply type? (This means that transcoding the source code could change program behaviour.)

I meant in terms of implying the "default" type. We're suggesting that default be char[], but if the literal contained unicode chars then the default might be something else. This is the method used to assign type to a char literal, but Walter has noted it might be confusing to do something similar with string literals.

Did you see my reply to you in this other thread .. wait a minute .. where's it gone .. no wonder you didn't reply, it seems my post was never made. Let me try again: digitalmars.D.learn/2216 What do you two think of what I have there?
 As indicated, I don't think this aspect is of much importance compared to
 the issues associated with an uncommited literal type ~ that uncommited
 aspect needs to be fixed, IMO.

I agree. While there exists a slight risk in doing so, it's no different to the risk involved with the current handling of integer literals. This change would essentailly make string literal handling consistent with integer literal handling. Regan
Nov 23 2005
next sibling parent "Kris" <fu bar.com> writes:
"Regan Heath" <regan netwin.co.nz> wrote
[snip]
 As indicated, I don't think this aspect is of much importance compared to
 the issues associated with an uncommited literal type ~ that uncommited
 aspect needs to be fixed, IMO.

I agree. While there exists a slight risk in doing so, it's no different to the risk involved with the current handling of integer literals. This change would essentailly make string literal handling consistent with integer literal handling.

Consistent with auto string-literals too.
Nov 23 2005
prev sibling parent reply Oskar Linde <oskar.lindeREM OVEgmail.com> writes:
Regan Heath wrote:
 On Wed, 23 Nov 2005 13:18:49 -0800, Kris <fu bar.com> wrote:
 
 "Oskar Linde" <oskar.lindeREM OVEgmail.com> wrote

 Kris wrote:

 There's the additional question as to whether the literal content  
 should
 be used to imply the type (like literal chars and numerics do), but
 that's a different topic and probably not as important.

How would the content imply the type? All Unicode strings are representable equally by char[], wchar[] and dchar[]. Do you mean that the most optimal (memory wise) encoding is used? Or do you mean that file encoding could imply type? (This means that transcoding the source code could change program behaviour.)

I meant in terms of implying the "default" type. We're suggesting that default be char[], but if the literal contained unicode chars then the default might be something else. This is the method used to assign type to a char literal, but Walter has noted it might be confusing to do something similar with string literals.


I think I see what you mean. By unicode char, you actually mean unicode character with code point > 127 (i.e. not representable in ASCII).
 Did you see my reply to you in this other thread .. wait a minute ..  
 where's it gone .. no wonder you didn't reply, it seems my post was 
 never  made. Let me try again:
 digitalmars.D.learn/2216
 
 What do you two think of what I have there?
 
 As indicated, I don't think this aspect is of much importance compared to
 the issues associated with an uncommited literal type ~ that uncommited
 aspect needs to be fixed, IMO.

I agree. While there exists a slight risk in doing so, it's no different to the risk involved with the current handling of integer literals. This change would essentailly make string literal handling consistent with integer literal handling.

Reasoning: The only risk always defaulting to char[] is in efficiency? Like the following scenario: A user writes string literals, in say chineese, without a suffix, making those strings char[] by default. Those literals are fed to functions having multiple implementations, optimised for char[], wchar[] and dchar[]. Since the optimal encoding for chineese is UTF-16 (guessing here), the users code will be suboptimal. You are hypothesizing that a heuristic could be used to pick a encoding depending on content. The heuristic you are considering seems to be: If the string contains characters not representable by a single UTF-16 code unit, make the string dchar[]. Else, if the string contains characters not representable by a single UTF-8 code unit, make the string wchar[]. Else, the string becomes char[]. Hmm... By having such a rule, you would also guarantee that: a) all indexing of string literals give valid unicode characters b) all slicing of string literals give valid unicode strings c) counting characters in a Unicode aware editor gives you the correct index Without such a rule, the following might give surprising results for "nave users"[0..5] a), b) and c) above seem to me to be quite strong arguments. I have almost convinced myself that there might be a good reason to have string literal types depend on content... :) /Oskar
Nov 23 2005
parent Georg Wrede <georg.wrede nospam.org> writes:
Oskar Linde wrote:
 Regan Heath wrote:
 On Wed, 23 Nov 2005 13:18:49 -0800, Kris <fu bar.com> wrote:
 "Oskar Linde" <oskar.lindeREM OVEgmail.com> wrote
 Kris wrote:
 
 There's the additional question as to whether the literal
 content should be used to imply the type (like literal chars
 and numerics do), but that's a different topic and probably
 not as important.

How would the content imply the type? All Unicode strings are representable equally by char[], wchar[] and dchar[]. Do you mean that the most optimal (memory wise) encoding is used? Or do you mean that file encoding could imply type? (This means that transcoding the source code could change program behaviour.)

I meant in terms of implying the "default" type. We're suggesting that default be char[], but if the literal contained unicode chars then the default might be something else. This is the method used to assign type to a char literal, but Walter has noted it might be confusing to do something similar with string literals.


I think I see what you mean. By unicode char, you actually mean unicode character with code point > 127 (i.e. not representable in ASCII).

I'd be willing to say that (see my other post in this thread, a couple of hours ago), the difference in execution time between having the string literal decoded from "suboptimal" to the needed type is negligible. And deciding based on content just makes things complicated. Both the deciding, the storing, and the retrieving. From that follows, that the time for Walter to do the code for that, is wasted. Much better to just store the literal in (whatever we, or actually Walter decide) just some type, and be done with it. At usage time it'd then get cast as needed, if needed. Simple.
 Did you see my reply to you in this other thread .. wait a minute
 .. where's it gone .. no wonder you didn't reply, it seems my post
 was never  made. Let me try again: 
 digitalmars.D.learn/2216
 
 What do you two think of what I have there?
 
 As indicated, I don't think this aspect is of much importance 
 compared to the issues associated with an uncommited literal type
 ~ that uncommited aspect needs to be fixed, IMO.

I agree. While there exists a slight risk in doing so, it's no different to the risk involved with the current handling of integer literals. This change would essentailly make string literal handling consistent with integer literal handling.

Reasoning: The only risk always defaulting to char[] is in efficiency? Like the following scenario: A user writes string literals, in say chineese, without a suffix, making those strings char[] by default. Those literals are fed to functions having multiple implementations, optimised for char[], wchar[] and dchar[]. Since the optimal encoding for chineese is UTF-16 (guessing here), the users code will be suboptimal.

Ok, let's have a vote: Let's say we have 100 000 French names, and we want to sort them. We have the same names in a char[][], wchar[][] and a dchar[][]. Which is fastest to sort? Say we have 100 000 Chinese names? Which is fastest? What if we have 100 000 English names? (Of course somebody will actually code and run this. But I'd like to hear it from folks _before_ that.)
Nov 23 2005
prev sibling parent reply Georg Wrede <georg.wrede nospam.org> writes:
Oskar Linde wrote:
 Georg Wrede wrote:
 Oskar Linde wrote:
 Georg Wrede wrote:

 We've wasted truckloads of ink lately on the UTF issue.

 The prayer:

 Please remove the *char*, *wchar* and *dchar* basic data types from 
 the documentation!

What atleast should be changed is the suggestion that the C char is replacable by the D char, and a slight change in definition: char: UTF-8 code unit wchar: UTF-16 code unit dchar: UTF-32 code unit and/or unicode character

A UTF-8 code unit can not be stored in char. [...]

Can it not? I thought I had been doing this all the time... Why? (I know most Unicode code points aka characters can not be stored in a char)

Like Regan pointed out, I meant code point.
 [...] Therefore UTF can't be
 mentioned at all in this context.

 By the same token, and because of symmetry, the wchar and dchar things 
 should vanish. Disappear. Get nuked.

A dchar can represent any Unicode character. Is that not enough reason to keep it?

No. What we need is to eradicate this entire issue from stealing bandwidth between the ears of every soul who reads the D documents.
 The language manual (as opposed to the Phobos docs), should not once 
 use the word UTF anywhere. Except possibly stating that a conformant 
 compiler has to accept source code files that are stored in UTF.

Why? It is often important to know the encoding of a string. (When dealing with system calls, c-library calls etc.) Doesn't D do the right thing to define Unicode as the character set and UTF-* as the supported encodings?

D docs, no. Phobos docs, yes. But only in std.utf, nowhere else.
 If a programmer decides to do UTF mangling, then he should store the 
 intermediate results in ubytes, ushorts and uints. This way he can 
 avoid getting tangled and tripped up before or later.

Those are more or less equivalent to char, wchar, dchar.

Those are exactly equivalent. The issue is not technical, compiler related, language related, anything. But, having char, wchar, and dchar gives the impression that they have something inherently to do with UTF, and therefore there's something special with them in D, as the docs now stand. That in turn, implies (to the reader, not necessarily to the writer), that there is some kind of difference in how D treats them, compared to ubyte, ushort and uint. Well, there is a difference. But that difference exists _only_ in char[] and wchar[]. From the docs however, the reader gets the impression that there is something in char, wchar and dchar themselves that differentiates them from whatever the reader previously may have assumed.
 The difference is more a matter of convention. (and string/character
 literal handling) Doesn't the confusion rather lie in the name? (char
 may imply character rather than code unit. I agree that this is
 unfortunate.)

Yes, yes! And that precisely is the issue here.
 And this way he keeps remembering that it's on his responsibility to 
 get things right.

 Please remove ""c, ""w and ""d from the documentation!

So you suggest that users should use an explicit cast instead?

No.

I think this may have been the reason for the implementation of the suffixes: print(char[] x) { printf("1\n"); } print(wchar[] x) { printf("2\n"); } void main() { print("hello"); } A remedy is very close to the current implementation. The following change in behaviour: string literals are always char[], but may be implicitly cast to wchar[] and dchar[]. print(char[] x) would therefore be a closer match. (All casts of literals are of course done at compile time.)

I'd have no problem with that. As long as we all agree on, that this is Because We Just Happened to Choose So -- and not because there'd be any Real Reason For Precisely This Choice. (That does sound stupid, but it's actually a very important distinction here.)
 Currently in D: string literals are __uncommitted char[] and may be 
 implicitly cast to char[], wchar[] and dchar[]. No cast takes preference.
 
 D may be too agnostic about preferred encoding...

Yes. The specters were lurking behind the back, so the programmer got a little paranoid in the night.
 How, or in what form the string literals get internally stored, is the 
 compiler vendor's own private matter. And definitely not part of a 
 language specification.

The form string literals are stored in affects the performance in many cases. Why remove this control from the programmer?

Because he really should not have to bother. (You might take an average program, count the literal strings, and then time the execution. Figure out the stupidest choice between UTF[8..32] and the OS's native encoding, and then calculate the time for decoding. I'd say that this amounts to such peanuts that it really is not worth thinking about.) If a programmer writes a 10kloc program, half of which is string literals, then maybe yes, it could make a measurable difference. OTOH, such a programmer's code probably has bigger performance issues (and others) anyhow.
 Rereading your post, tryig to understand what you ask for leads me to 
 assume that by your suggestion, a poor, but conforming, compiler may 
 include a hidden call to a conversion function and a hidden memory 
 allocation in this function call:
 
 foo("hello");

Yes. Don't buy anythin from that company.
 The string literal decorations only create a huge amount of 
 distraction, sending every programmer on a wild goose chase, possibly 
 several times, before they either finds someone who explains things, 
 or they switch away from D.

I can not understand this confusion. It is currently very well specified how a character literal gets stored (and you get to pick between 3 different encodings).

This confusion is unnecessary, and based on a misconception. And I dare say, most of this confusion is directly a result from _having_ the string literal decorations in the first place.
 The problem lies in the "" form, where you have 
 not specified the encoding. The compiler will try to infer the encoding 
 depending on context. This is a weakness i think should be fixed by:
 
 - "" is char[], but may be implicitly cast to dchar[] and wchar[]

That would fix it technically. I'd vote yes. The bigger thing to fix is the rest. (char not being code point, gotchas when having arrays of char which you then slice, etc. -- still have to be sorted out.)
 Behind the scenes, a smart compiler manufacturer probably stores all 
 string literals as UTF-8. Nice. Or as some other representation that's 
 convenient for him, be it UTF-whatever, or even a native encoding. In 
 any case, the compiler knows what this representation is.

 When the string gets used (gets assigned to a variable, or put in a 
 structure, or printed to screen), then the compiler should implicitly 
 cast (as in toUTFxxx and not the current "cast") the string to what's 
 expected.

I start to understand you now... (first time reading)
 We can have "string types", like [c/w/d]char[], but not standalone UTF 
 chars. When the string literal gets assigned to any of these, then it 
 should get converted.

 Actually, a smart compiler would already store the string literal in 
 the width the string will get used, it's got the info right there in 
 the same source file. [...]


 [...] And in case the programmer is real dumb and assigns the same 
 literal to more than one UTF width, it could be stored in all of those 
 separately. -- But the brain cells of the compiler writer should be 
 put to more productive issues than this.

How do you assign _one_ literal to more than one variable?

Gee, thanks! My bad. Oh-oh, it's not my bad, after all. If another literal with the same content gets assigned in other places, it's customary for the compiler to only store one copy of it in the binary. So, of course then, _that_ compiler might then store it in different encodings if it is assigned to different width variables in the source.
 The D programmer should not necessarily even know that representation. 
 The only situation he would need to know it is if his program goes 
 directly to the executable memory image snooping for the literal. I'm 
 not sure that should be legal.

What is the wrong with a well defined representation?

First of all, if the machine is big endian or little endian. What if it wants to store them in an unexpected place? Maybe it's a CIA certified compiler that encrypts all literals in binaries and inserts on-the-fly runtime decoding routines in all string fetches? (I REALLY wouldn't be surprised to hear they have one.) Thousands of reasons why you'd be very interested in _not_ knowing the representation. "What you don't know doesn't hurt you, and at least it doesn't borrow brain cells from you." for(byte i=0; i<10; i++) {printfln("foo ", i);} Do you honestly know whether i is a byte or an int in the compiled program? Should you even care? How many have even thought about it? --- Having said that, if somebody asks me, I'd vote for UTF-8 on Linux, and whatever is appropriate on Windows. Then I could look for the strings in the binary file with the unix "strings" command.
Nov 23 2005
parent =?ISO-8859-1?Q?Jari-Matti_M=E4kel=E4?= <jmjmak invalid_utu.fi> writes:
Georg Wrede wrote:

<snip>

 (You might take an average program, count the literal strings, and then 
 time the execution. Figure out the stupidest choice between UTF[8..32] 
 and the OS's native encoding, and then calculate the time for decoding. 
 I'd say that this amounts to such peanuts that it really is not worth 
 thinking about.)
 
 If a programmer writes a 10kloc program, half of which is string 
 literals, then maybe yes, it could make a measurable difference. OTOH, 
 such a programmer's code probably has bigger performance issues (and 
 others) anyhow.

anyone wants to convert 200 kB strings while drawing a 3d scene etc. IMHO this UTF-thing is a problem since some people here don't want to write their own libraries and would like the compiler to do everything for them. I totally agree that we should have only one type of string structure. I write Unicode-compliant programs every week and have never used these wchar/dchar structures. What I would really like is a Unicode-stream class that could read/write valid Unicode text files.
 The problem lies in the "" form, where you have not specified the 
 encoding. The compiler will try to infer the encoding depending on 
 context. This is a weakness i think should be fixed by:

 - "" is char[], but may be implicitly cast to dchar[] and wchar[]

That would fix it technically. I'd vote yes. The bigger thing to fix is the rest. (char not being code point, gotchas when having arrays of char which you then slice, etc. -- still have to be sorted out.)

I don't believe this is a big problem. This works correctly already: foreach(wchar c; char[] unicodestring) { ... } Walter should fix this so that to following would work too: foreach(char c; char[] unicodestring) { ... } BTW, should the sorting of char-arrays be a language or library feature?
 What is the wrong with a well defined representation?

First of all, if the machine is big endian or little endian. What if it wants to store them in an unexpected place? Maybe it's a CIA certified compiler that encrypts all literals in binaries and inserts on-the-fly runtime decoding routines in all string fetches? (I REALLY wouldn't be surprised to hear they have one.)

today... go get some sleep, man :)
 Having said that, if somebody asks me, I'd vote for UTF-8 on Linux, and 
 whatever is appropriate on Windows. Then I could look for the strings in 
 the binary file with the unix "strings" command.

UTF-8 on Linux. Maybe UTF-16 on Windows (performance)? OTOH, UTF-8 has serious advantages over UTF-7/16/32 [1], [2] (some of us appreciate other things than just raw performance) [1] http://www.everything2.com/index.pl?node=UTF-8 [2] http://en.wikipedia.org/wiki/Utf-8
Nov 23 2005