Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.compilers > #908
| From | glen herrmannsfeldt <gah@ugcs.caltech.edu> |
|---|---|
| Newsgroups | comp.compilers |
| Subject | Re: precedence have both ways |
| Date | 2013-05-31 05:10 +0000 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <13-05-022@comp.compilers> (permalink) |
| References | <13-05-010@comp.compilers> <13-05-018@comp.compilers> <13-05-020@comp.compilers> |
Joe keane <jgk@panix.com> wrote: (snip) > This reminds me of a question. > One person designs a language 'C1' with precedence: > > [higher] > ... > | > & > <, <=, >, <= > ==, != > ... > [lower] > Some other person designs a language 'C2' with precedence: Looks not so far from B, see: http://cm.bell-labs.com/cm/cs/who/dmr/bref.pdf > [higher] > ... > <, <=, >, <= > ==, != > | > & > ... > [lower] > They're the same besides that. > To compromise, they make a new language 'C3' such that a program is > valid C3 if it is valid C1 and valid C2 -and- both ways mean the same. Seems easy if you disallow the use of the operators with changed precedence without appropriate ()'s. > Is there some good way to do this -in the grammar-? As above, put the restriction in the grammar. As I understand it, not having actually ever programmed in B, (but found the reference manual) B only had the bitwise operators, and shared them (used them also for) the logical operators. The had (and have) the appropriate precedence. When C inherited them from B, and then added the && and || operators, the previous & and | operators kept their precedence. For actual use as bitwise operators, such as masks, it would be more convenient if they had higher precedence. As it is, they pretty much always are parenthesized. (Easy to forget and generate wrong results.) -- glen
Back to comp.compilers | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Articles/books that discuss separating the context-free part of a language from the context-sensitive part? "Costello, Roger L." <costello@mitre.org> - 2013-05-17 20:57 +0000
Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-05-18 00:18 +0000
Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? Gene Wirchenko <genew@telus.net> - 2013-05-19 18:02 -0700
Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-05-20 03:17 +0000
Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? Aleksey Demakov <ademakov@gmail.com> - 2013-05-18 16:52 +0400
Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-20 10:53 +0000
Re: Articles/books that discuss separating the context-free part of a language from the context-sensitive part? Gene Wirchenko <genew@telus.net> - 2013-05-20 23:24 -0700
precedence have both ways jgk@panix.com (Joe keane) - 2013-05-30 23:21 -0400
Re: precedence have both ways glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2013-05-31 05:10 +0000
Re: precedence have both ways anton@mips.complang.tuwien.ac.at (Anton Ertl) - 2013-05-31 10:54 +0000
csiph-web