regexp question: match anything but not a group?

regexp question: match anything but not a group?

[Thorsten Jolitz]

Hi List, 

how can I write a regexp that acts like e.g.

,------
| ".*?"
`------

but does not match a group like e.g. 

,---------------------
| (regexp-quote "\\)")
`---------------------

?

This works more or less but does not seem to be very robust

,---------
| "[^)]*?"
`---------

since ')' could appear in other contexts than the group. How can I
negate a specific group of characters and not only any occurence of
single characters?

-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Pascal J. Bourguignon]

Thorsten Jolitz <tjolitz@gmail.com> writes:

> Hi List, 
>
> how can I write a regexp that acts like e.g.
>
> ,------
> | ".*?"
> `------
>
> but does not match a group like e.g. 
>
> ,---------------------
> | (regexp-quote "\\)")
> `---------------------
>
> ?
>
> This works more or less but does not seem to be very robust
>
> ,---------
> | "[^)]*?"
> `---------
>
> since ')' could appear in other contexts than the group. How can I
> negate a specific group of characters and not only any occurence of
> single characters?

(defun pjb-rx-not-string (string)
  (case  (length string)
    ((0)        `(* anything))
    ((1)        `(not (any ,string)))
    (otherwise  `(or (not (any ,(subseq string 0 1)))
                     (seq ,(subseq string 0 1)
                          ,(pjb-rx-not-string (subseq string 1)))))))


(defun pjb-regexp-not-string (string)
  (let ((all (coerce (delete-duplicates
                      (sort (coerce string 'list) (function <))) 'string)))
    (rx-to-string `(seq bot
                        (* (not (any ,string)))
                        ,(pjb-rx-not-string string)
                        (* (not (any ,string)))
                        eot))))

(pjb-regexp-not-string "\\)")
--> "\\(?:\\`[^)\\]*\\(?:[^\\]\\|\\\\[^)]\\)[^)\\]*\\'\\)"


-- 
__Pascal Bourguignon__
http://www.informatimago.com/
"Le mercure monte ?  C'est le moment d'acheter !"

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

"Pascal J. Bourguignon" <pjb@informatimago.com> writes:

> Thorsten Jolitz <tjolitz@gmail.com> writes:
>
>> Hi List, 
>>
>> how can I write a regexp that acts like e.g.
>>
>> ,------
>> | ".*?"
>> `------
>>
>> but does not match a group like e.g. 
>>
>> ,---------------------
>> | (regexp-quote "\\)")
>> `---------------------
>>
>> ?
>>
>> This works more or less but does not seem to be very robust
>>
>> ,---------
>> | "[^)]*?"
>> `---------
>>
>> since ')' could appear in other contexts than the group. How can I
>> negate a specific group of characters and not only any occurence of
>> single characters?
>
> (defun pjb-rx-not-string (string)
>   (case  (length string)
>     ((0)        `(* anything))
>     ((1)        `(not (any ,string)))
>     (otherwise  `(or (not (any ,(subseq string 0 1)))
>                      (seq ,(subseq string 0 1)
>                           ,(pjb-rx-not-string (subseq string 1)))))))
>
>
> (defun pjb-regexp-not-string (string)
>   (let ((all (coerce (delete-duplicates
>                       (sort (coerce string 'list) (function <))) 'string)))
>     (rx-to-string `(seq bot
>                         (* (not (any ,string)))
>                         ,(pjb-rx-not-string string)
>                         (* (not (any ,string)))
>                         eot))))
>
> (pjb-regexp-not-string "\\)")
> --> "\\(?:\\`[^)\\]*\\(?:[^\\]\\|\\\\[^)]\\)[^)\\]*\\'\\)"

Wow, impressive, thank you. 

At first sight reads like pseudo-code to me, probably more CL-style than
elisp style. 

any, anything, otherwise ... unusual stuff, I don't even find those
functions with C-h f (not even after loading cl.el and cl-extra.el). 

This is definitely hard to digest ...

-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Pascal J. Bourguignon]

Thorsten Jolitz <tjolitz@gmail.com> writes:

> "Pascal J. Bourguignon" <pjb@informatimago.com> writes:
>
>> Thorsten Jolitz <tjolitz@gmail.com> writes:
>>
>>> Hi List, 
>>>
>>> how can I write a regexp that acts like e.g.
>>>
>>> ,------
>>> | ".*?"
>>> `------
>>>
>>> but does not match a group like e.g. 
>>>
>>> ,---------------------
>>> | (regexp-quote "\\)")
>>> `---------------------
>>>
>>> ?
>>>
>>> This works more or less but does not seem to be very robust
>>>
>>> ,---------
>>> | "[^)]*?"
>>> `---------
>>>
>>> since ')' could appear in other contexts than the group. How can I
>>> negate a specific group of characters and not only any occurence of
>>> single characters?
>>
>> (defun pjb-rx-not-string (string)
>>   (case  (length string)
>>     ((0)        `(* anything))
>>     ((1)        `(not (any ,string)))
>>     (otherwise  `(or (not (any ,(subseq string 0 1)))
>>                      (seq ,(subseq string 0 1)
>>                           ,(pjb-rx-not-string (subseq string 1)))))))
>>
>>
>> (defun pjb-regexp-not-string (string)
>>   (let ((all (coerce (delete-duplicates
>>                       (sort (coerce string 'list) (function <))) 'string)))
>>     (rx-to-string `(seq bot
>>                         (* (not (any ,string)))
>>                         ,(pjb-rx-not-string string)
>>                         (* (not (any ,string)))
>>                         eot))))
>>
>> (pjb-regexp-not-string "\\)")
>> --> "\\(?:\\`[^)\\]*\\(?:[^\\]\\|\\\\[^)]\\)[^)\\]*\\'\\)"
>
> Wow, impressive, thank you. 
>
> At first sight reads like pseudo-code to me, probably more CL-style than
> elisp style. 
>
> any, anything, otherwise ... unusual stuff, I don't even find those
> functions with C-h f (not even after loading cl.el and cl-extra.el). 
>
> This is definitely hard to digest ...

rx is a famous emacs lisp library. (require 'rx)
case is in (require 'cl) which should be in everybody's ~/.emacs
The rest is DATA!    


all wasn't used, it's for a little optimization:

(defun pjb-regexp-not-string (string)
  (let ((chars (coerce (delete-duplicates
                        (sort (coerce string 'list) (function <))) 'string)))
    (rx-to-string `(seq bot
                        (* (not (any ,chars)))
                        ,(pjb-rx-not-string string)
                        (* (not (any ,chars)))
                        eot))))

-- 
__Pascal Bourguignon__
http://www.informatimago.com/
"Le mercure monte ?  C'est le moment d'acheter !"

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

"Pascal J. Bourguignon" <pjb@informatimago.com> writes:

> Thorsten Jolitz <tjolitz@gmail.com> writes:
>
>> "Pascal J. Bourguignon" <pjb@informatimago.com> writes:
>>
>>> Thorsten Jolitz <tjolitz@gmail.com> writes:
>>>
>>>> Hi List, 
>>>>
>>>> how can I write a regexp that acts like e.g.
>>>>
>>>> ,------
>>>> | ".*?"
>>>> `------
>>>>
>>>> but does not match a group like e.g. 
>>>>
>>>> ,---------------------
>>>> | (regexp-quote "\\)")
>>>> `---------------------
>>>>
>>>> ?
>>>>
>>>> This works more or less but does not seem to be very robust
>>>>
>>>> ,---------
>>>> | "[^)]*?"
>>>> `---------
>>>>
>>>> since ')' could appear in other contexts than the group. How can I
>>>> negate a specific group of characters and not only any occurence of
>>>> single characters?
>>>
>>> (defun pjb-rx-not-string (string)
>>>   (case  (length string)
>>>     ((0)        `(* anything))
>>>     ((1)        `(not (any ,string)))
>>>     (otherwise  `(or (not (any ,(subseq string 0 1)))
>>>                      (seq ,(subseq string 0 1)
>>>                           ,(pjb-rx-not-string (subseq string 1)))))))
>>>
>>>
>>> (defun pjb-regexp-not-string (string)
>>>   (let ((all (coerce (delete-duplicates
>>>                       (sort (coerce string 'list) (function <))) 'string)))
>>>     (rx-to-string `(seq bot
>>>                         (* (not (any ,string)))
>>>                         ,(pjb-rx-not-string string)
>>>                         (* (not (any ,string)))
>>>                         eot))))
>>>
>>> (pjb-regexp-not-string "\\)")
>>> --> "\\(?:\\`[^)\\]*\\(?:[^\\]\\|\\\\[^)]\\)[^)\\]*\\'\\)"
>>
>> Wow, impressive, thank you. 
>>
>> At first sight reads like pseudo-code to me, probably more CL-style than
>> elisp style. 
>>
>> any, anything, otherwise ... unusual stuff, I don't even find those
>> functions with C-h f (not even after loading cl.el and cl-extra.el). 
>>
>> This is definitely hard to digest ...
>
> rx is a famous emacs lisp library. (require 'rx)

I've seen that one ...
Ok, being aware of rx.el the whole thing appears less crytic. 

> case is in (require 'cl) which should be in everybody's ~/.emacs

I know 'case from PicoLisp and really like it. If only the cl 'case
would compare with equal too and not only with eql...

> The rest is DATA!    

yes, I know, but still ... not the usual elisp you see everyday. 

> all wasn't used, it's for a little optimization:
>
> (defun pjb-regexp-not-string (string)
>   (let ((chars (coerce (delete-duplicates
>                         (sort (coerce string 'list) (function <))) 'string)))
>     (rx-to-string `(seq bot
>                         (* (not (any ,chars)))
>                         ,(pjb-rx-not-string string)
>                         (* (not (any ,chars)))
>                         eot))))

I begin to understand ...

-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Andreas Röhler]

Am 01.04.2014 23:30, schrieb Thorsten Jolitz:
>
> Hi List,
>
> how can I write a regexp that acts like e.g.
>
> ,------
> | ".*?"
> `------
>

BTW looks wrong. .* might much nothing, if non-greedy it remains nothing (?)

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

Andreas Röhler <andreas.roehler@easy-emacs.de> writes:

> Am 01.04.2014 23:30, schrieb Thorsten Jolitz:
>>
>> Hi List,
>>
>> how can I write a regexp that acts like e.g.
>>
>> ,------
>> | ".*?"
>> `------
>>
>
> BTW looks wrong. .* might much nothing, if non-greedy it remains
> nothing (?)

But it still seems valid to protect against greedyness?

,---------------------------------------------------------------------
| '*?', '+?', '??'
|     These are "non-greedy" variants of the operators '*', '+' and '?
|     '. Where those operators match the largest possible substring
|     (consistent with matching the entire containing expression), the
|     non-greedy variants match the smallest possible substring
|     (consistent with matching the entire containing expression).
|    
|     For example, the regular expression 'c[ad]*a' when applied to
|     the string 'cdaaada' matches the whole string; but the regular
|     expression 'c[ad]*?a', applied to that same string, matches just
|     'cda'. (The smallest possible match here for '[ad]*?' that
|     permits the whole expression to match is 'd'.)
`---------------------------------------------------------------------


-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Stefan Monnier]

> But it still seems valid to protect against greedyness?
                                              ^^^^^^^^^^
AKA greed,


        Stefan

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> But it still seems valid to protect against greedyness?
>                                               ^^^^^^^^^^
> AKA greed,

I just made it up, but funny enough - it does actually exist (with
slightly different spelling)!

From http://www.collinsdictionary.com/dictionary/english/greediness:

,-------------------------------------------------------------------
| greediness (ˈɡriːdɪnɪs) 
| 
| Definitions
| 
| noun
| 
|  1. the quality of being greedy
| 
| greedy (ˈɡriːdɪ Pronunciation for greedy ) 
| 
| Definitions
| 
| adjective
| 
| Word forms:  greedier,  greediest
| 
|  1. excessively desirous of food or wealth, esp in large amounts;
|     voracious
|  2. (postpositive) foll by for eager (for)   ⇒ `a man greedy for
|     success'
| 
| Derived Forms
| 
| ˈgreedily adverb
| ˈgreediness noun
| 
| Word Origin
| 
| Old English grǣdig; related to Old Norse grāthugr, Gothic grēdags
| hungry, Old High German grātac
| 
| Example Sentences Including 'greediness'
| 
|     At times his greediness got the better of him but he never let
|     his enthusiasm go off the boil.
| 
| Sun, News of the World (2004)
| 
|     Broilers consume lots more feed-there's a good chance that
|     greediness has been inadvertently selected for.
| 
| New Scientist (1998)
| 
|     Mr Carman asked him if he had a `streak of greediness " in him
|     for money, expensive cars and Rolex watches.
| 
| Sun, News of the World (1999)
| 
|     Thus individuals who do experience strong pulls of greediness
|     often go to desperate measures to hide their behaviour.
| 
| Knowles, Jane Know Your Own Mind
`-------------------------------------------------------------------

-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Loris Bennett]

Thorsten Jolitz <tjolitz@gmail.com> writes:

> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>
>>> But it still seems valid to protect against greedyness?
>>                                               ^^^^^^^^^^
>> AKA greed,
>
> I just made it up, but funny enough - it does actually exist (with
> slightly different spelling)!
>
>>From http://www.collinsdictionary.com/dictionary/english/greediness:
>
> ,-------------------------------------------------------------------
> | greediness (ˈɡriːdɪnɪs) 
> | 
> | Definitions
> | 
> | noun
> | 
> |  1. the quality of being greedy
> | 
> | greedy (ˈɡriːdɪ Pronunciation for greedy ) 
> | 
> | Definitions
> | 
> | adjective
> | 
> | Word forms:  greedier,  greediest
> | 
> |  1. excessively desirous of food or wealth, esp in large amounts;
> |     voracious
> |  2. (postpositive) foll by for eager (for)   ⇒ `a man greedy for
> |     success'
> | 
> | Derived Forms
> | 
> | ˈgreedily adverb
> | ˈgreediness noun
> | 
> | Word Origin
> | 
> | Old English grǣdig; related to Old Norse grāthugr, Gothic grēdags
> | hungry, Old High German grātac
> | 
> | Example Sentences Including 'greediness'
> | 
> |     At times his greediness got the better of him but he never let
> |     his enthusiasm go off the boil.
> | 
> | Sun, News of the World (2004)
> | 
> |     Broilers consume lots more feed-there's a good chance that
> |     greediness has been inadvertently selected for.
> | 
> | New Scientist (1998)
> | 
> |     Mr Carman asked him if he had a `streak of greediness " in him
> |     for money, expensive cars and Rolex watches.
> | 
> | Sun, News of the World (1999)
> | 
> |     Thus individuals who do experience strong pulls of greediness
> |     often go to desperate measures to hide their behaviour.
> | 
> | Knowles, Jane Know Your Own Mind
> `-------------------------------------------------------------------

If I were you, Thorsten, I wouldn't rely on "The Sun and "NOTW" for
particularly nuanced usage of the English language, even if Collins does
quote them.  "New Scientist" is in a different category, but I think
"greed" would be much better in the example given for the following
reason:

I would say that "greed" is traditionally "a deadly sin", i.e. a moral
failing, whereas "greediness" is a (normally) non-fatal display of
overindulgence.  Bankers may be reviled for their greed, but
sticky-faced children told off for their greediness.

In "Mastering Regular Expressions", Friedl refers to the "greediness"
aspect of regular expressions, which, given the lack of a moral context,
seems to me the appropriate choice.

Cheers,

Loris

-- 
This signature is currently under construction.

Re: regexp question: match anything but not a group?

[Andreas Röhler]

Am 04.04.2014 11:04, schrieb Loris Bennett:
> Thorsten Jolitz <tjolitz@gmail.com> writes:
>
>> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>
>>>> But it still seems valid to protect against greedyness?
>>>                                                ^^^^^^^^^^
>>> AKA greed,
>>
>> I just made it up, but funny enough - it does actually exist (with
>> slightly different spelling)!
>>
>> >From http://www.collinsdictionary.com/dictionary/english/greediness:
>>
>> ,-------------------------------------------------------------------
>> | greediness (ˈɡriːdɪnɪs)
>> |
>> | Definitions
>> |
>> | noun
>> |
>> |  1. the quality of being greedy
>> |
>> | greedy (ˈɡriːdɪ Pronunciation for greedy )
>> |
>> | Definitions
>> |
>> | adjective
>> |
>> | Word forms:  greedier,  greediest
>> |
>> |  1. excessively desirous of food or wealth, esp in large amounts;
>> |     voracious
>> |  2. (postpositive) foll by for eager (for)   ⇒ `a man greedy for
>> |     success'
>> |
>> | Derived Forms
>> |
>> | ˈgreedily adverb
>> | ˈgreediness noun
>> |
>> | Word Origin
>> |
>> | Old English grǣdig; related to Old Norse grāthugr, Gothic grēdags
>> | hungry, Old High German grātac
>> |
>> | Example Sentences Including 'greediness'
>> |
>> |     At times his greediness got the better of him but he never let
>> |     his enthusiasm go off the boil.
>> |
>> | Sun, News of the World (2004)
>> |
>> |     Broilers consume lots more feed-there's a good chance that
>> |     greediness has been inadvertently selected for.
>> |
>> | New Scientist (1998)
>> |
>> |     Mr Carman asked him if he had a `streak of greediness " in him
>> |     for money, expensive cars and Rolex watches.
>> |
>> | Sun, News of the World (1999)
>> |
>> |     Thus individuals who do experience strong pulls of greediness
>> |     often go to desperate measures to hide their behaviour.
>> |
>> | Knowles, Jane Know Your Own Mind
>> `-------------------------------------------------------------------
>
> If I were you, Thorsten, I wouldn't rely on "The Sun and "NOTW" for
> particularly nuanced usage of the English language, even if Collins does
> quote them.  "New Scientist" is in a different category, but I think
> "greed" would be much better in the example given for the following
> reason:
>
> I would say that "greed" is traditionally "a deadly sin", i.e. a moral
> failing, whereas "greediness" is a (normally) non-fatal display of
> overindulgence.  Bankers may be reviled for their greed, but
> sticky-faced children told off for their greediness.
>
> In "Mastering Regular Expressions", Friedl refers to the "greediness"
> aspect of regular expressions, which, given the lack of a moral context,
> seems to me the appropriate choice.
>
> Cheers,
>
> Loris
>

"greediness" sounds a little bit wrapped, sorted, objective - while "greed" evokes the living beast. :)

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

"Loris Bennett" <loris.bennett@fu-berlin.de> writes:

> Thorsten Jolitz <tjolitz@gmail.com> writes:
>
>> Stefan Monnier <monnier@iro.umontreal.ca> writes:
>>
>>>> But it still seems valid to protect against greedyness?
>>>                                               ^^^^^^^^^^
>>> AKA greed,
>>
>> I just made it up, but funny enough - it does actually exist (with
>> slightly different spelling)!
>>
>>>From http://www.collinsdictionary.com/dictionary/english/greediness:
>>
>> ,-------------------------------------------------------------------
>> | greediness (ˈɡriːdɪnɪs) 
>> | 
>> | Definitions
>> | 
>> | noun
>> | 
>> |  1. the quality of being greedy
>> | 
>> | greedy (ˈɡriːdɪ Pronunciation for greedy ) 
>> | 
>> | Definitions
>> | 
>> | adjective
>> | 
>> | Word forms:  greedier,  greediest
>> | 
>> |  1. excessively desirous of food or wealth, esp in large amounts;
>> |     voracious
>> |  2. (postpositive) foll by for eager (for)   ⇒ `a man greedy for
>> |     success'
>> | 
>> | Derived Forms
>> | 
>> | ˈgreedily adverb
>> | ˈgreediness noun
>> | 
>> | Word Origin
>> | 
>> | Old English grǣdig; related to Old Norse grāthugr, Gothic grēdags
>> | hungry, Old High German grātac
>> | 
>> | Example Sentences Including 'greediness'
>> | 
>> |     At times his greediness got the better of him but he never let
>> |     his enthusiasm go off the boil.
>> | 
>> | Sun, News of the World (2004)
>> | 
>> |     Broilers consume lots more feed-there's a good chance that
>> |     greediness has been inadvertently selected for.
>> | 
>> | New Scientist (1998)
>> | 
>> |     Mr Carman asked him if he had a `streak of greediness " in him
>> |     for money, expensive cars and Rolex watches.
>> | 
>> | Sun, News of the World (1999)
>> | 
>> |     Thus individuals who do experience strong pulls of greediness
>> |     often go to desperate measures to hide their behaviour.
>> | 
>> | Knowles, Jane Know Your Own Mind
>> `-------------------------------------------------------------------
>
> If I were you, Thorsten, I wouldn't rely on "The Sun and "NOTW" for
> particularly nuanced usage of the English language, even if Collins does
> quote them.  "New Scientist" is in a different category, but I think
> "greed" would be much better in the example given for the following
> reason:
>
> I would say that "greed" is traditionally "a deadly sin", i.e. a moral
> failing, whereas "greediness" is a (normally) non-fatal display of
> overindulgence.  Bankers may be reviled for their greed, but
> sticky-faced children told off for their greediness.
>
> In "Mastering Regular Expressions", Friedl refers to the "greediness"
> aspect of regular expressions, which, given the lack of a moral context,
> seems to me the appropriate choice.

At least nuanced usage of the English language is still a topic. Here in
Germany we are almost back to Martin Luthers free-style phonetic
spelling after decades of so called 'language reforms' ;)

-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Andreas Röhler]

Am 04.04.2014 12:40, schrieb Thorsten Jolitz:

> At least nuanced usage of the English language is still a topic. Here in
> Germany we are almost back to Martin Luthers free-style phonetic
> spelling after decades of so called 'language reforms' ;)
>

I'm afraid we are fallen behind of 2000 years cultural development, before the ancient Greeks and Jesus Christ.
And not just in Germany, the whole so-called western world.

Re: regexp question: match anything but not a group?

[Andreas Röhler]

Am 03.04.2014 21:36, schrieb Thorsten Jolitz:
> Andreas Röhler <andreas.roehler@easy-emacs.de> writes:
>
>> Am 01.04.2014 23:30, schrieb Thorsten Jolitz:
>>>
>>> Hi List,
>>>
>>> how can I write a regexp that acts like e.g.
>>>
>>> ,------
>>> | ".*?"
>>> `------
>>>
>>
>> BTW looks wrong. .* might much nothing, if non-greedy it remains
>> nothing (?)
>
> But it still seems valid to protect against greedyness?
>

Coming upon evaluating this, cursor at start of "asdf":

(progn (looking-at ".*")(message (match-string-no-properties 0)))asdf

==> asdf

(progn (looking-at ".*?")(message (match-string-no-properties 0)))asdf

==> ""

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

Andreas Röhler <andreas.roehler@easy-emacs.de> writes:

> Am 03.04.2014 21:36, schrieb Thorsten Jolitz:
>> Andreas Röhler <andreas.roehler@easy-emacs.de> writes:
>>
>>> Am 01.04.2014 23:30, schrieb Thorsten Jolitz:
>>>>
>>>> Hi List,
>>>>
>>>> how can I write a regexp that acts like e.g.
>>>>
>>>> ,------
>>>> | ".*?"
>>>> `------
>>>>
>>>
>>> BTW looks wrong. .* might much nothing, if non-greedy it remains
>>> nothing (?)
>>
>> But it still seems valid to protect against greedyness?
>>
>
> Coming upon evaluating this, cursor at start of "asdf":
>
> (progn (looking-at ".*")(message (match-string-no-properties 0)))asdf
>
> ==> asdf
>
> (progn (looking-at ".*?")(message (match-string-no-properties 0)))asdf
>
> ==> ""


Yes, it seems you are right ... so this is actually always wrong?
Thanks for the tip ...

-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

Thorsten Jolitz <tjolitz@gmail.com> writes:

> Hi List, 
>
> how can I write a regexp that acts like e.g.
>
> ,------
> | ".*?"
> `------
>
> but does not match a group like e.g. 
>
> ,---------------------
> | (regexp-quote "\\)")
> `---------------------
>
> ?
>
> This works more or less but does not seem to be very robust
>
> ,---------
> | "[^)]*?"
> `---------
>
> since ')' could appear in other contexts than the group. How can I
> negate a specific group of characters and not only any occurence of
> single characters?

I figured that I actually need something even smarter, because what I
really want is a regexp A that matches a given other regexp B if it is a
regexp-group, or not otherwise.

The best version of that regexp A I can come up with right now is
something like this:

#+begin_src emacs-lisp
  (concat "^"                         ; BOL
          (regexp-quote "\\(")        ; group begins
          "\\(\\?[[:digit:]]*:\\)?"   ; shy or explicitly numbered group?
          "[^\\000]+?"                ; any char, idea copied from org-mode
          (regexp-quote "\\)")        ; group ends
          "[*+]?[?]?"                 ; quantifier
          "$")                        ; EOL
#+end_src

The problem is that in the content part

,------------------------------------------------------------------
| "[^\\000]+?"                ; any char, idea copied from org-mode
`------------------------------------------------------------------

anything can happen, and any number of opening and/or closing parents
and sub-groups can appear, so I really need to determine if

,-----------------------------------------
| (regexp-quote "\\)")        ; group ends
`-----------------------------------------

closes 

,-------------------------------------------
| (regexp-quote "\\(")        ; group begins
`-------------------------------------------

and thats kind of hard to do with regexp syntax. 

I know now that I could simulate *look-ahead-assertions* for my original
problem, which aren't implemented in Emacs AFAIK, something on the line
of:

#+begin_src emacs-lisp
(progn
  (and (looking-at ".*")
       (not (eq (char-after) ?\))
       (not (eq (char-after (+ 1 (point)) MY-CHAR)))
       (not (eq (char-after (+ 2 (point)) MY-CHAR)))
       [...]
       ))
#+end_src

but counting and bookkeeping of opening and closing parens in regexp B
looks too difficult to me.

I can only imagine to check parens with lisp first (e.g. by using
`forward-sexp' or so) and then use a regexp like above that does not
care what is inside the group enclosing parens.

Then I could drop this part from the regexp too

,----------------------------------------------------------------
| "\\(\\?[[:digit:]]*:\\)?"   ; shy or explicitly numbered group?
`----------------------------------------------------------------

because all that counts are the matching parens.

Any ideas how to best check if a given regexp is a regexp group or not?

-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Andreas Röhler]

Am 01.04.2014 23:30, schrieb Thorsten Jolitz:
>
> Hi List,
>
> how can I write a regexp that acts like e.g.
>
> ,------
> | ".*?"
> `------
>
> but does not match a group like e.g.
>
> ,---------------------
> | (regexp-quote "\\)")
> `---------------------
>
> ?
>
> This works more or less but does not seem to be very robust
>
> ,---------
> | "[^)]*?"
> `---------
>
> since ')' could appear in other contexts than the group. How can I
> negate a specific group of characters and not only any occurence of
> single characters?
>


You need look-ahead-assertions, which aren't implemented in Emacs AFAIK.
Here is a workaround to play with:

(progn
   (and (looking-at ".*")
        (not (eq (char-after) ?\))))
   (message "%s" (match-string-no-properties 0)))

Test with more than one char ahead writing n char-after:

(not (eq (char-after (+ 1 (point)) MY-CHAR)))
(not (eq (char-after (+ 2 (point)) MY-CHAR)))

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

Andreas Röhler <andreas.roehler@easy-emacs.de> writes:

> Am 01.04.2014 23:30, schrieb Thorsten Jolitz:
>>
>> Hi List,
>>
>> how can I write a regexp that acts like e.g.
>>
>> ,------
>> | ".*?"
>> `------
>>
>> but does not match a group like e.g.
>>
>> ,---------------------
>> | (regexp-quote "\\)")
>> `---------------------
>>
>> ?
>>
>> This works more or less but does not seem to be very robust
>>
>> ,---------
>> | "[^)]*?"
>> `---------
>>
>> since ')' could appear in other contexts than the group. How can I
>> negate a specific group of characters and not only any occurence of
>> single characters?
>>
>
>
> You need look-ahead-assertions, which aren't implemented in Emacs AFAIK.
> Here is a workaround to play with:
>
> (progn
>   (and (looking-at ".*")
>        (not (eq (char-after) ?\))))
>   (message "%s" (match-string-no-properties 0)))
>
> Test with more than one char ahead writing n char-after:
>
> (not (eq (char-after (+ 1 (point)) MY-CHAR)))
> (not (eq (char-after (+ 2 (point)) MY-CHAR)))

Since gmane.org was down sometime, this thread was continued with PMs,
so, just for reference, here is my solution to an extended form of the
original problem (i.e. determine if a given regexp is a regexp group or
not):

,-------------------------------------------------------
| Andreas Röhler <andreas.roehler@easy-emacs.de> writes:
| 
| > Which would extend the question...
| > You wanted not to match any
| >
| > (regexp-quote "\\)")
| 
| I think I got it:
| 
| #+begin_src emacs-lisp
| (defun tj/regexp-group-p (rgxp)
|   "Return RGXP if its a regexp group, nil otherwise."
|   (with-temp-buffer
|     (insert (format "%S" rgxp))
|     (goto-char (point-min))
|     (if (ignore-errors
|           (save-excursion
|             (and
|              (re-search-forward "(")
|              (save-match-data
|                (looking-back
|                 (concat "^" (regexp-quote "\"\\\\("))
|                 (line-beginning-position)))
|              (goto-char (match-beginning 0))
|              (progn
|                (forward-sexp)
|                (looking-at
|                 "[*+]?[?]?\"$")))))
|         rgxp nil)))
| #+end_src
| 
| Thanks for you help!
`-------------------------------------------------------

-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Bob Proulx]

Thorsten Jolitz wrote:
> Since gmane.org was down sometime, this thread was continued with PMs,
> so, ...

I realize that many people read the mailing list through the web
archives, through the news interface, and so forth.  But it is a
mailing list!  If you are going to send private mail because one of
the web archives is down you could just as easily send email to the
mailing list as it is intended to be used.  <me wags finger/>  :-)

Bob

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

Bob Proulx <bob@proulx.com> writes:

> Thorsten Jolitz wrote:
>> Since gmane.org was down sometime, this thread was continued with PMs,
>> so, ...
>
> I realize that many people read the mailing list through the web
> archives, through the news interface, and so forth.  But it is a
> mailing list!  If you are going to send private mail because one of
> the web archives is down you could just as easily send email to the
> mailing list as it is intended to be used.  <me wags finger/>  :-)

I received private mails and answered privately ... took me a while to
figure out that gmane is down and these were just copies of mailing list
posts.

Somehow the news interface is so much nicer, and as you say, many people
seem to use it. 

-- 
cheers,
Thorsten

Re: regexp question: match anything but not a group?

[Stefan Monnier]

> You need look-ahead-assertions, which aren't implemented in Emacs AFAIK.

Actually, what he needs is negation.  In Perl regexp, negation is
provided via look-ahead assertions, but in lex.el, they're provided as the
"normal negation operator".  I.e. in lex.el (negate RE) is a regular
expression which matches any string not matched by RE.


        Stefan

Re: regexp question: match anything but not a group?

[Thorsten Jolitz]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> You need look-ahead-assertions, which aren't implemented in Emacs AFAIK.
>
> Actually, what he needs is negation.  In Perl regexp, negation is
> provided via look-ahead assertions, but in lex.el, they're provided as the
> "normal negation operator".  I.e. in lex.el (negate RE) is a regular
> expression which matches any string not matched by RE.

Very useful, thanks, I just installed lex.el.

-- 
cheers,
Thorsten