* occur API change proposal
@ 2007-11-29 16:02 Ted Zlatanov
2007-12-01 0:34 ` Juri Linkov
0 siblings, 1 reply; 7+ messages in thread
From: Ted Zlatanov @ 2007-11-29 16:02 UTC (permalink / raw)
To: emacs-devel
This can wait until after the next release.
I propose changing the occur API to allow an optional predicate
function. For example, this is useful to invert a regular expression so
you don't have to run occur on the whole buffer matching everything,
then limit the results.
Ted
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: occur API change proposal
2007-11-29 16:02 occur API change proposal Ted Zlatanov
@ 2007-12-01 0:34 ` Juri Linkov
2008-08-05 18:49 ` add INVERT to re-search-{forward, backward} (was: occur API change proposal) Ted Zlatanov
0 siblings, 1 reply; 7+ messages in thread
From: Juri Linkov @ 2007-12-01 0:34 UTC (permalink / raw)
To: Ted Zlatanov; +Cc: emacs-devel
> I propose changing the occur API to allow an optional predicate
> function. For example, this is useful to invert a regular expression so
> you don't have to run occur on the whole buffer matching everything,
> then limit the results.
The occur engine currently hard-codes the function call of
`re-search-forward'. Instead of this, we could do the same
as is done already in isearch for customization of the search
function using a variable `isearch-search-fun-function', and
add a new analogous variable `occur-fun-function'.
Even though such a variable will be useful for other purposes,
no simple function will allow inverting a regular expression.
Implementing this feature requires significant modification in
the logic of the occur engine: either changing the algorithm to
call `looking-at' at every line (very inefficient), or recording
a position of the previous match and outputing lines between it
and the current position (not easy to customize).
--
Juri Linkov
http://www.jurta.org/emacs/
^ permalink raw reply [flat|nested] 7+ messages in thread
* add INVERT to re-search-{forward, backward} (was: occur API change proposal)
2007-12-01 0:34 ` Juri Linkov
@ 2008-08-05 18:49 ` Ted Zlatanov
2008-08-25 15:45 ` Juri Linkov
0 siblings, 1 reply; 7+ messages in thread
From: Ted Zlatanov @ 2008-08-05 18:49 UTC (permalink / raw)
To: emacs-devel
On Sat, 01 Dec 2007 02:34:35 +0200 Juri Linkov <juri@jurta.org> wrote:
>> I propose changing the occur API to allow an optional predicate
>> function. For example, this is useful to invert a regular expression so
>> you don't have to run occur on the whole buffer matching everything,
>> then limit the results.
JL> The occur engine currently hard-codes the function call of
JL> `re-search-forward'. Instead of this, we could do the same
JL> as is done already in isearch for customization of the search
JL> function using a variable `isearch-search-fun-function', and
JL> add a new analogous variable `occur-fun-function'.
JL> Even though such a variable will be useful for other purposes,
JL> no simple function will allow inverting a regular expression.
JL> Implementing this feature requires significant modification in
JL> the logic of the occur engine: either changing the algorithm to
JL> call `looking-at' at every line (very inefficient), or recording
JL> a position of the previous match and outputing lines between it
JL> and the current position (not easy to customize).
After thinking about this (yes, it sat in my TODO queue for a while) I
realize the problem is fundamental: Emacs doesn't have a way to invert
at the re-search-{forward,backward} API level. There's no way to
automatically invert a regular expression into another regular
expression, so this change must happen at the API level to avoid
unpleasant workarounds as Juri describes.
I propose simply adding an optional INVERT parameter to those two
functions. The API cost is small with an optional parameter, though I
don't know if performance will be affected by the extra check on every
search cycle.
Once this API is in place, making the change in occur-mode and other
places to use the new API is very easy.
Ted
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: add INVERT to re-search-{forward, backward} (was: occur API change proposal)
2008-08-05 18:49 ` add INVERT to re-search-{forward, backward} (was: occur API change proposal) Ted Zlatanov
@ 2008-08-25 15:45 ` Juri Linkov
2008-08-25 15:57 ` add INVERT to re-search-{forward, backward} Lennart Borgman (gmail)
0 siblings, 1 reply; 7+ messages in thread
From: Juri Linkov @ 2008-08-25 15:45 UTC (permalink / raw)
To: Ted Zlatanov; +Cc: emacs-devel
>>> I propose changing the occur API to allow an optional predicate
>>> function. For example, this is useful to invert a regular expression so
>>> you don't have to run occur on the whole buffer matching everything,
>>> then limit the results.
>
> JL> The occur engine currently hard-codes the function call of
> JL> `re-search-forward'. Instead of this, we could do the same
> JL> as is done already in isearch for customization of the search
> JL> function using a variable `isearch-search-fun-function', and
> JL> add a new analogous variable `occur-fun-function'.
>
> JL> Even though such a variable will be useful for other purposes,
> JL> no simple function will allow inverting a regular expression.
> JL> Implementing this feature requires significant modification in
> JL> the logic of the occur engine: either changing the algorithm to
> JL> call `looking-at' at every line (very inefficient), or recording
> JL> a position of the previous match and outputing lines between it
> JL> and the current position (not easy to customize).
>
> After thinking about this (yes, it sat in my TODO queue for a while) I
> realize the problem is fundamental: Emacs doesn't have a way to invert
> at the re-search-{forward,backward} API level. There's no way to
> automatically invert a regular expression into another regular
> expression, so this change must happen at the API level to avoid
> unpleasant workarounds as Juri describes.
>
> I propose simply adding an optional INVERT parameter to those two
> functions. The API cost is small with an optional parameter, though I
> don't know if performance will be affected by the extra check on every
> search cycle.
>
> Once this API is in place, making the change in occur-mode and other
> places to use the new API is very easy.
It seems such an API with a new INVERT parameter will be useless
because these two character-based search functions will find too much
matches. For example, calling it with the parameter "def" on the string
"abcdefghi" will match in it 6 places, i.e. everywhere except the
position under the character "d". Thus this will provide no useful
information to occur.
Instead of this, I think the change should be done at the occur level,
since occur's algorithm is line-based and can skip lines that contain
a given regexp. This could be similar to the algorithm used by the
command `flush-lines' in the same file. `occur' currently works like the
command `keep-lines' that keeps lines containing the specified regexp.
But with a new INVERT argument, `occur' could work like `flush-lines' that
keep everything except lines containing the specified regexp.
--
Juri Linkov
http://www.jurta.org/emacs/
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: add INVERT to re-search-{forward, backward}
2008-08-25 15:45 ` Juri Linkov
@ 2008-08-25 15:57 ` Lennart Borgman (gmail)
2008-08-25 19:45 ` Juri Linkov
0 siblings, 1 reply; 7+ messages in thread
From: Lennart Borgman (gmail) @ 2008-08-25 15:57 UTC (permalink / raw)
To: Juri Linkov; +Cc: Ted Zlatanov, emacs-devel
Juri Linkov wrote:
> Instead of this, I think the change should be done at the occur level,
> since occur's algorithm is line-based and can skip lines that contain
> a given regexp. This could be similar to the algorithm used by the
> command `flush-lines' in the same file. `occur' currently works like the
> command `keep-lines' that keeps lines containing the specified regexp.
> But with a new INVERT argument, `occur' could work like `flush-lines' that
> keep everything except lines containing the specified regexp.
This is also similar to grep etc.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: add INVERT to re-search-{forward, backward}
2008-08-25 15:57 ` add INVERT to re-search-{forward, backward} Lennart Borgman (gmail)
@ 2008-08-25 19:45 ` Juri Linkov
2008-08-25 20:07 ` Lennart Borgman (gmail)
0 siblings, 1 reply; 7+ messages in thread
From: Juri Linkov @ 2008-08-25 19:45 UTC (permalink / raw)
To: Lennart Borgman (gmail); +Cc: Ted Zlatanov, emacs-devel
>> Instead of this, I think the change should be done at the occur level,
>> since occur's algorithm is line-based and can skip lines that contain
>> a given regexp. This could be similar to the algorithm used by the
>> command `flush-lines' in the same file. `occur' currently works like the
>> command `keep-lines' that keeps lines containing the specified regexp.
>> But with a new INVERT argument, `occur' could work like `flush-lines' that
>> keep everything except lines containing the specified regexp.
>
> This is also similar to grep etc.
Yes, as a line-oriented tool, grep's -v --invert-match option is what
could be modelled in occur.
Then a negative prefix argument of `occur' could mean inverting the
regexp and displaying non-matching lines.
--
Juri Linkov
http://www.jurta.org/emacs/
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: add INVERT to re-search-{forward, backward}
2008-08-25 19:45 ` Juri Linkov
@ 2008-08-25 20:07 ` Lennart Borgman (gmail)
0 siblings, 0 replies; 7+ messages in thread
From: Lennart Borgman (gmail) @ 2008-08-25 20:07 UTC (permalink / raw)
To: Juri Linkov; +Cc: Ted Zlatanov, emacs-devel
Juri Linkov wrote:
>>> Instead of this, I think the change should be done at the occur level,
>>> since occur's algorithm is line-based and can skip lines that contain
>>> a given regexp. This could be similar to the algorithm used by the
>>> command `flush-lines' in the same file. `occur' currently works like the
>>> command `keep-lines' that keeps lines containing the specified regexp.
>>> But with a new INVERT argument, `occur' could work like `flush-lines' that
>>> keep everything except lines containing the specified regexp.
>> This is also similar to grep etc.
>
> Yes, as a line-oriented tool, grep's -v --invert-match option is what
> could be modelled in occur.
>
> Then a negative prefix argument of `occur' could mean inverting the
> regexp and displaying non-matching lines.
Maybe it also would be practical to be able to access that function from
within the occur window too?
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2008-08-25 20:07 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2007-11-29 16:02 occur API change proposal Ted Zlatanov
2007-12-01 0:34 ` Juri Linkov
2008-08-05 18:49 ` add INVERT to re-search-{forward, backward} (was: occur API change proposal) Ted Zlatanov
2008-08-25 15:45 ` Juri Linkov
2008-08-25 15:57 ` add INVERT to re-search-{forward, backward} Lennart Borgman (gmail)
2008-08-25 19:45 ` Juri Linkov
2008-08-25 20:07 ` Lennart Borgman (gmail)
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