Re: Inconsistent regex behaviour in 7.4.383
Tim Brosnan wrote:
I initially send a version of this message through the google groups
interface, but it seems to have disappeared. Apologies if there is
duplication.
When going through some regex examples from
VimRegexTutor(https://github.com/dahu/VimRegexTutor) I found that one of
the examples did not match the provided text when run in 7.4.383. Here
is the regex and the sample text:
*30* : Find Text between HTML tags
/\%(\1\)\@=.*\%(\/\(\w\+\)\)\@=
OR
/\v%(\\1\)@=.*%(\\/(\w+)\)@=
levelCan I play, daddy?/level
Neither of the provided regexs would watch the sample text (it should
match the text between html tags). However, when I tried 7.1.42 (only
other version at hand) I found that the text between tags was matched
correctly. Both versions were fun as -u NONE and set nocompatible to
try to rule out option or plugin clashes.
Is this is a bug or has regex behaviour changed between 7.1.42 and 7.4.383?
I don't think the pattern is supposed to work. The backreference is
before the capturing group. It's a suprise it works at all. Probably
because in the old regex engine the \@= part is used only after
finding a match for the rest.
It's a very inefficient pattern too, better use:
/\(\w\+\).\{-}\zs.*\ze\/\1
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Re: Inconsistent regex behaviour in 7.4.383
On 30-Jul-2014 12:53 +0200, Bram Moolenaar wrote:
Tim Brosnan wrote:
I initially send a version of this message through the google groups
interface, but it seems to have disappeared. Apologies if there is
duplication.
When going through some regex examples from
VimRegexTutor(https://github.com/dahu/VimRegexTutor) I found that one of
the examples did not match the provided text when run in 7.4.383. Here
is the regex and the sample text:
*30* : Find Text between HTML tags
/\%(\1\)\@=.*\%(\/\(\w\+\)\)\@=
OR
/\v%(\\1\)@=.*%(\\/(\w+)\)@=
levelCan I play, daddy?/level
Neither of the provided regexs would watch the sample text (it should
match the text between html tags). However, when I tried 7.1.42 (only
other version at hand) I found that the text between tags was matched
correctly. Both versions were fun as -u NONE and set nocompatible to
try to rule out option or plugin clashes.
Is this is a bug or has regex behaviour changed between 7.1.42 and 7.4.383?
I don't think the pattern is supposed to work. The backreference is
before the capturing group.
Well, it does work in the old engine.
It's a suprise it works at all. Probably because in the old regex
engine the \@= part is used only after finding a match for the
rest.
It's a very inefficient pattern too, better use:
/\(\w\+\).\{-}\zs.*\ze\/\1
You cannot always use \zs in place of \@= (for example, with :syntax
match, or when already using a \zs elsewhere in the pattern).
Just changing the example in the help isn't going to solve the problem
of backwards compatibility. I think the new engine either has to support
it, or detect that special situation and then dynamically switch to the
old engine (like \%#=1 does).
-- regards, ingo
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Re: Inconsistent regex behaviour in 7.4.383
On Wednesday, July 30, 2014 6:58:11 AM UTC-5, Ingo Karkat wrote: It's a suprise it works at all. Probably because in the old regex engine the \@= part is used only after finding a match for the rest. The help for /\@= pretty explicitly says it should work this way, and why: The part of the pattern after \@= and \@! are checked for a match first, thus things like \1 don't work to reference \(\) inside the preceding atom. It does work the other way around: Example matches ~ \1\@=,\([a-z]\+\) ,abc in abc,abc It's weird but it's too late now. So I agree with Ingo: either the regex engine must be switched dynamically to use the old engine by default when an undefined backreference is used, or the new regex engine should support it in the same order. -- -- You received this message from the vim_dev maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups vim_dev group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Inconsistent regex behaviour in 7.4.383
I initially send a version of this message through the google groups interface, but it seems to have disappeared. Apologies if there is duplication. When going through some regex examples from VimRegexTutor(https://github.com/dahu/VimRegexTutor) I found that one of the examples did not match the provided text when run in 7.4.383. Here is the regex and the sample text: *30* : Find Text between HTML tags /\%(\1\)\@=.*\%(\/\(\w\+\)\)\@= OR /\v%(\\1\)@=.*%(\\/(\w+)\)@= levelCan I play, daddy?/level Neither of the provided regexs would watch the sample text (it should match the text between html tags). However, when I tried 7.1.42 (only other version at hand) I found that the text between tags was matched correctly. Both versions were fun as -u NONE and set nocompatible to try to rule out option or plugin clashes. Is this is a bug or has regex behaviour changed between 7.1.42 and 7.4.383? -- -- You received this message from the vim_dev maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups vim_dev group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: Inconsistent regex behaviour in 7.4.383
On Tuesday, July 29, 2014 3:10:56 PM UTC-5, Tim Brosnan wrote: I initially send a version of this message through the google groups interface, but it seems to have disappeared. Apologies if there is duplication. When going through some regex examples from VimRegexTutor(https://github.com/dahu/VimRegexTutor) I found that one of the examples did not match the provided text when run in 7.4.383. Here is the regex and the sample text: *30* : Find Text between HTML tags /\%(\1\)\@=.*\%(\/\(\w\+\)\)\@= OR /\v%(\\1\)@=.*%(\\/(\w+)\)@= levelCan I play, daddy?/level Neither of the provided regexs would watch the sample text (it should match the text between html tags). However, when I tried 7.1.42 (only other version at hand) I found that the text between tags was matched correctly. Both versions were fun as -u NONE and set nocompatible to try to rule out option or plugin clashes. Is this is a bug or has regex behaviour changed between 7.1.42 and 7.4.383? I think this is the same issue reported here: https://groups.google.com/d/topic/vim_dev/07qFhT34nEI/discussion Probably it is caused by the new regular expression engine introduced in 7.4. See :help new-regexp-engine and :help two-engines for more details. The new engine is designed in a way that backreferences are really difficult. In the thread I link above Bram calls it a miracle that they work at all. :help 'regexpengine' provides a possible workaround for you until this gets fixed. Try doing :set regexpengine=1 to see if that fixes it for you temporarily until the problem is fixed. -- -- You received this message from the vim_dev maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups vim_dev group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: Inconsistent regex behaviour in 7.4.383
On Tuesday, July 29, 2014 9:20:02 PM UTC+1, Ben Fritz wrote: On Tuesday, July 29, 2014 3:10:56 PM UTC-5, Tim Brosnan wrote: I initially send a version of this message through the google groups interface, but it seems to have disappeared. Apologies if there is duplication. When going through some regex examples from VimRegexTutor(https://github.com/dahu/VimRegexTutor) I found that one of the examples did not match the provided text when run in 7.4.383. Here is the regex and the sample text: *30* : Find Text between HTML tags /\%(\1\)\@=.*\%(\/\(\w\+\)\)\@= OR /\v%(\\1\)@=.*%(\\/(\w+)\)@= levelCan I play, daddy?/level Neither of the provided regexs would watch the sample text (it should match the text between html tags). However, when I tried 7.1.42 (only other version at hand) I found that the text between tags was matched correctly. Both versions were fun as -u NONE and set nocompatible to try to rule out option or plugin clashes. Is this is a bug or has regex behaviour changed between 7.1.42 and 7.4.383? I think this is the same issue reported here: https://groups.google.com/d/topic/vim_dev/07qFhT34nEI/discussion Probably it is caused by the new regular expression engine introduced in 7.4. See :help new-regexp-engine and :help two-engines for more details. The new engine is designed in a way that backreferences are really difficult. In the thread I link above Bram calls it a miracle that they work at all. :help 'regexpengine' provides a possible workaround for you until this gets fixed. Try doing :set regexpengine=1 to see if that fixes it for you temporarily until the problem is fixed. Ah, it seems like this is the problem. :set regexpengine=1 gives the correct behaviour. I didn't know about version7.txt, it certainly makes tracking differences between updates easier. Thanks for your help. -- -- You received this message from the vim_dev maillist. Do not top-post! Type your reply below the text you are replying to. For more information, visit http://www.vim.org/maillist.php --- You received this message because you are subscribed to the Google Groups vim_dev group. To unsubscribe from this group and stop receiving emails from it, send an email to vim_dev+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
