C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Regex-friendly "raw" string literals          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message Scott Meyers Guest Posted: Sat Feb 11, 2006 8:06 am    Post subject: Regex-friendly "raw" string literals Last September, Marcus posted the following here: I've seen that the library technical report includes a regular expression library. However, since regular expressions use a lot of backslashes (\w, \1, etc.) and they are escape characters in C++ strings, the programmer has to write things like this: "\\w" and "\\\\" for regexps "\w" and "\\", respectively. Have raw-strings been considered to simplify these cases? For example, Python and D work like this: r"\w" == "\\w" r"c:\tsd" == "c:\\tsd" (D has an alternate syntax for this feature, using backticks: `\w`, which allow double quotes inside the string) C# uses an @ before the string (@"c:\omf" == "c:\\omf"). IMHO, this kind of lexical sugar makes the language a lot easier to work with (at least for those who use regexps and such) and they don't complicate the language (it's just a lexical change). There were no followups, which surprises me, because it seems to me that supporting "raw" string literals is an excellent way to facilitate experimentation by non-C++-experts with the regex support in TR1. My understanding is that a goal of C++0x is to make C++ easier for non-experts to use. IMO, it's a lot easier for a non-expert programmer to get this right, std::string zipFileRegex("\w\.zip"); than this: std::string zipFileRegex("\\w\\.zip"); (As an aside, if the regex above is wrong, that's partly my point. It's hard enough to come up with the right regex in the first place without having to simultaneously worry about whether all the regex backslashes have been themselves backslashed.) I googled around for discussion of unobvious problems arising from adding a "raw" string literal to C++, but I didn't find anything. Is there something I'm overlooking? Also, my understanding is that the door has closed on core language extensions for C++0x. Is that the case? If so, presumably there is no chance for "raw" string literals to enter C++0x even if somebody writes up a proposal, right? Thanks, Scott --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Pete Becker Guest Posted: Sat Feb 11, 2006 6:06 pm    Post subject: Re: Regex-friendly "raw" string literals Scott Meyers wrote: Quote: IMO, it's a lot easier for a non-expert programmer to get this right, std::string zipFileRegex("\w\.zip"); than this: std::string zipFileRegex("\\w\\.zip"); Agreed. But one of the constraints that we imposed on TR1 was that it should be implementable without compiler changes, that is, it's supposed to be entirely library. (There are a few places where an implementation can do a better job with compiler help, but the requirements were written so that they can be met without it). Quote: Also, my understanding is that the door has closed on core language extensions for C++0x. Is that the case? Nope. Get moving! -- Pete Becker Dinkumware, Ltd. (http://www.dinkumware.com) --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Francis Glassborow Guest Posted: Sun Feb 12, 2006 6:06 am    Post subject: Re: Regex-friendly "raw" string literals In article <3dadnSiIy65FgHPenZ2dnUVZ_tCdnZ2d (AT) giganews (DOT) com>, Pete Becker <petebecker (AT) acm (DOT) org> writes Quote: Also, my understanding is that the door has closed on core language extensions for C++0x. Is that the case? Nope. Get moving! Sorry Pete, but he was effectively correct. The Evolution Group does not intend to consider new proposals (unless already covered by existing papers). -- Francis Glassborow ACCU Author of 'You Can Do It!' see http://www.spellen.org/youcandoit For project ideas and contributions: http://www.spellen.org/youcandoit/projects --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Pete Becker Guest Posted: Mon Feb 13, 2006 8:06 pm    Post subject: Re: Regex-friendly "raw" string literals Francis Glassborow wrote: Quote: In article <3dadnSiIy65FgHPenZ2dnUVZ_tCdnZ2d (AT) giganews (DOT) com>, Pete Becker petebecker (AT) acm (DOT) org> writes Also, my understanding is that the door has closed on core language extensions for C++0x. Is that the case? Nope. Get moving! Sorry Pete, but he was effectively correct. The Evolution Group does not intend to consider new proposals (unless already covered by existing papers). The Evolution Working Group is not the only route for language changes. -- Pete Becker Dinkumware, Ltd. (http://www.dinkumware.com) --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Ron House Guest Posted: Tue Feb 14, 2006 4:06 am    Post subject: Language changes. Was: Regex-friendly "raw" string literals. Pete Becker wrote: Quote: The Evolution Working Group is not the only route for language changes. What's a suitable route for this time frame? -- Ron House house (AT) usq (DOT) edu.au http://www.sci.usq.edu.au/staff/house --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Francis Glassborow Guest Posted: Tue Feb 14, 2006 4:06 am    Post subject: Re: Regex-friendly "raw" string literals In article <3Yednd-AH6yK0HLeRVn-ig (AT) giganews (DOT) com>, Pete Becker <petebecker (AT) acm (DOT) org> writes Quote: The Evolution Working Group is not the only route for language changes. I think it is for changes to the core of the language. -- Francis Glassborow ACCU Author of 'You Can Do It!' see http://www.spellen.org/youcandoit For project ideas and contributions: http://www.spellen.org/youcandoit/projects --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Pete Becker Guest Posted: Tue Feb 14, 2006 3:36 pm    Post subject: Re: Regex-friendly "raw" string literals Francis Glassborow wrote: Quote: In article <3Yednd-AH6yK0HLeRVn-ig (AT) giganews (DOT) com>, Pete Becker petebecker (AT) acm (DOT) org> writes The Evolution Working Group is not the only route for language changes. I think it is for changes to the core of the language. I think the core group is in charge of the core of the language. -- Pete Becker Dinkumware, Ltd. (http://www.dinkumware.com) --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Francis Glassborow Guest Posted: Tue Feb 14, 2006 7:06 pm    Post subject: Re: Regex-friendly "raw" string literals In article <mNSdnaFKVMfiV2zenZ2dnUVZ_tudnZ2d (AT) giganews (DOT) com>, Pete Becker <petebecker (AT) acm (DOT) org> writes Quote: Francis Glassborow wrote: In article <3Yednd-AH6yK0HLeRVn-ig (AT) giganews (DOT) com>, Pete Becker petebecker (AT) acm (DOT) org> writes The Evolution Working Group is not the only route for language changes. I think it is for changes to the core of the language. I think the core group is in charge of the core of the language. Yes, indeed it is, but under current policy it does not consider new language features other than those coming out of the evolution group who are the people tasked with considering proposals for new features. -- Francis Glassborow ACCU Author of 'You Can Do It!' see http://www.spellen.org/youcandoit For project ideas and contributions: http://www.spellen.org/youcandoit/projects --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.jamesd.demon.co.uk/csc/faq.html ] Back to top Thorsten Ottosen Guest Posted: Sun Feb 19, 2006 10:47 pm    Post subject: Re: Regex-friendly "raw" string literals Scott Meyers wrote: Quote: Last September, Marcus posted the following here: IMO, it's a lot easier for a non-expert programmer to get this right, std::string zipFileRegex("\w\.zip"); than this: std::string zipFileRegex("\\w\\.zip"); (As an aside, if the regex above is wrong, that's partly my point. It's hard enough to come up with the right regex in the first place without having to simultaneously worry about whether all the regex backslashes have been themselves backslashed.) Also, my understanding is that the door has closed on core language extensions for C++0x. Is that the case? If so, presumably there is no chance for "raw" string literals to enter C++0x even if somebody writes up a proposal, right? A major concern has been making C++ easier to use and teach, so the raw strings seems relevant. However, maybe we don't need a core-language change. Many languages has a library with a small utility string escape( const string& ); this can then be called from within the regex constructor. IIUC, constructing a regex is a fairly heavy operation, so running escaping a string also should be releatively easy. -Thorsten --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. 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