Re: The length of strings vs. # of chars vs. sizeof
Bill Baxter wbax...@gmail.com wrote: On Tue, Nov 3, 2009 at 2:47 AM, rmcguire rjmcgu...@gmail.com wrote: Charles Hixson charleshi...@earthlink.net wrote: Jesse Phillips wrote: On Sun, 01 Nov 2009 11:36:31 -0800, Charles Hixson wrote: Does anyone just *know* the answer? (And if so, could they make the documentation explicit?) I believe the documentation you are looking for is: http://www.prowiki.org/wiki4d/wiki.cgi?DanielKeep/TextInD It is more about understanding UTF than it is about learning strings. Thanks, that does appear to be the answer. So if a string is too long, and I shorten it by one character, I'd better test it with std.utf.validate(str). If it doesn't throw an error, it's ok. Otherwise shorten it again and retry. I hope I understood this correctly. (I'm sure there's a more elegant way to do this, but here I'm going for a simple approach, as I should rarely be encountering this problem.) As far as I know if you want to shorten a utf8 string you just check the first bit of the last byte to see if its 0. If its 0 go back further until you find a byte that starts with 1, and then remove that byte too. All characters start with a byte that starts with 1, the number of 1s in the first byte of the character tell you how many bytes in the character. Hope that helps, but you should find a library that already has a shorten my string function. It's explained well in Andrei's book. 0* -- single byte character 11* -- first byte of multi-byte char 10* -- subsequent byte of multi-byte char --bb :) forgot about that, its been a while since I played with utf8. made a Hessian serializer in C. -Rory
Re: The length of strings vs. # of chars vs. sizeof
Bill Baxter wrote: On Tue, Nov 3, 2009 at 2:47 AM, rmcguirerjmcgu...@gmail.com wrote: Charles Hixsoncharleshi...@earthlink.net wrote: Jesse Phillips wrote: On Sun, 01 Nov 2009 11:36:31 -0800, Charles Hixson wrote: Does anyone just *know* the answer? (And if so, could they make the documentation explicit?) I believe the documentation you are looking for is: http://www.prowiki.org/wiki4d/wiki.cgi?DanielKeep/TextInD It is more about understanding UTF than it is about learning strings. Thanks, that does appear to be the answer. So if a string is too long, and I shorten it by one character, I'd better test it with std.utf.validate(str). If it doesn't throw an error, it's ok. Otherwise shorten it again and retry. I hope I understood this correctly. (I'm sure there's a more elegant way to do this, but here I'm going for a simple approach, as I should rarely be encountering this problem.) As far as I know if you want to shorten a utf8 string you just check the first bit of the last byte to see if its 0. If its 0 go back further until you find a byte that starts with 1, and then remove that byte too. All characters start with a byte that starts with 1, the number of 1s in the first byte of the character tell you how many bytes in the character. Hope that helps, but you should find a library that already has a shorten my string function. It's explained well in Andrei's book. 0* -- single byte character 11* -- first byte of multi-byte char 10* -- subsequent byte of multi-byte char --bb Thanks. That's a much better answer.
Re: The length of strings vs. # of chars vs. sizeof
Jesse Phillips wrote: On Sun, 01 Nov 2009 11:36:31 -0800, Charles Hixson wrote: Does anyone just *know* the answer? (And if so, could they make the documentation explicit?) I believe the documentation you are looking for is: http://www.prowiki.org/wiki4d/wiki.cgi?DanielKeep/TextInD It is more about understanding UTF than it is about learning strings. Thanks, that does appear to be the answer. So if a string is too long, and I shorten it by one character, I'd better test it with std.utf.validate(str). If it doesn't throw an error, it's ok. Otherwise shorten it again and retry. I hope I understood this correctly. (I'm sure there's a more elegant way to do this, but here I'm going for a simple approach, as I should rarely be encountering this problem.)
The length of strings vs. # of chars vs. sizeof
I've read and re-read the documentation, but I can't decide whether a UTF-8 character that takes multiple bytes to express counts as one or multiple values in length and sizeof. Sizeof seems to presume that all entries are the same length, but otherwise it seems to be the property I need. (I suppose that I could just enter a string that I know is multi-byte chars, but it sure would be better if I could find out from the documentation.) I'm pretty certain that it just counts as one character for indexing, so length would almost need to also count the number of characters rather than bytes. Sizeof *should* be the correct property, and I've been assuming that it is, but I'm a bit afraid that I'll run across some unexpected character and it won't act the way I think it should. And the documentation reads ambiguously. Does anyone just *know* the answer? (And if so, could they make the documentation explicit?)
Re: The length of strings vs. # of chars vs. sizeof
Charles Hixson wrote: I've read and re-read the documentation, but I can't decide whether a UTF-8 character that takes multiple bytes to express counts as one or multiple values in length and sizeof. Sizeof seems to presume that all entries are the same length, but otherwise it seems to be the property I need. (I suppose that I could just enter a string that I know is multi-byte chars, but it sure would be better if I could find out from the documentation.) I'm pretty certain that it just counts as one character for indexing, so length would almost need to also count the number of characters rather than bytes. Strings are just arrays of code units. Their length is the number of elements (i.e. code units) they contain, just like other arrays. A code point may comprise multiple code units, and a logical character may comprise multiple code points. The latter is true even with dchar/utf-32. -- Rainer Deyke - rain...@eldwood.com
Re: The length of strings vs. # of chars vs. sizeof
Rainer Deyke wrote: Charles Hixson wrote: I've read and re-read the documentation, but I can't decide whether a UTF-8 character that takes multiple bytes to express counts as one or multiple values in length and sizeof. Sizeof seems to presume that all entries are the same length, but otherwise it seems to be the property I need. (I suppose that I could just enter a string that I know is multi-byte chars, but it sure would be better if I could find out from the documentation.) I'm pretty certain that it just counts as one character for indexing, so length would almost need to also count the number of characters rather than bytes. Strings are just arrays of code units. Their length is the number of elements (i.e. code units) they contain, just like other arrays. A code point may comprise multiple code units, and a logical character may comprise multiple code points. The latter is true even with dchar/utf-32. So, in UTF-8, length is the number of bytes in the string and sizeof is 8 (on 32-bits systems). Jerome -- mailto:jeber...@free.fr http://jeberger.free.fr Jabber: jeber...@jabber.fr signature.asc Description: OpenPGP digital signature
Re: The length of strings vs. # of chars vs. sizeof
On Sun, 01 Nov 2009 11:36:31 -0800, Charles Hixson wrote: Does anyone just *know* the answer? (And if so, could they make the documentation explicit?) I believe the documentation you are looking for is: http://www.prowiki.org/wiki4d/wiki.cgi?DanielKeep/TextInD It is more about understanding UTF than it is about learning strings.
Re: The length of strings vs. # of chars vs. sizeof
Jérôme M. Berger wrote: Rainer Deyke wrote: Strings are just arrays of code units. Their length is the number of elements (i.e. code units) they contain, just like other arrays. A code point may comprise multiple code units, and a logical character may comprise multiple code points. The latter is true even with dchar/utf-32. So, in UTF-8, length is the number of bytes in the string and sizeof is 8 (on 32-bits systems). Yes. -- Rainer Deyke - rain...@eldwood.com
Re: The length of strings vs. # of chars vs. sizeof
Rainer Deyke wrote: Jesse Phillips wrote: I believe the documentation you are looking for is: http://www.prowiki.org/wiki4d/wiki.cgi?DanielKeep/TextInD It is more about understanding UTF than it is about learning strings. One thing that page fails to mention is that D has no awareness of anything higher-level than code points. In particular: - dchar contains a code point, not a logical character. - D has no awareness of canonical forms and precomposed/decomposed characters (at the language level). (Some characters can be represented as either one or two code points. D does not know that these are supposed to represent the same character.) - Although D stops you from outputting an incomplete code point, it does not stop you from outputting an incomplete logical character. Also, some D library functions only work on the ASCII subset of utf-8. Well, it *is* on a Wiki.
