query-replace-regexp ... "Invalid repacement string '\.'"

query-replace-regexp ... "Invalid repacement string '\.'"

[s. keeling]

Hi.  I was trying to make it easy on myself using q-r-r replacing
'[^\]\.' (not a backslash, followed by a literal dot/period) with the
string (sans quotes) '\.', essentially "escaping" every dot/period in
the file.  "M-x query-replace" had no trouble with it but M-x
query-replace-regexp refused, spouting the error message in the
subject.

So how do you replace '.' with '\.' in emacs?  Googling's
(groups.google.com) turned up nothing useful (interesting, but not
useful).  I tried variations of '\\\.' (literal backslash followed by
literal period) to no effect.

Suggestions or pointers welcome.  Thanks.


-- 
Any technology distinguishable from magic is insufficiently advanced.
(*)    http://www.spots.ab.ca/~keeling          Linux Counter #80292
- -    http://www.faqs.org/rfcs/rfc1855.html    Please, don't Cc: me.
       Spammers! http://www.spots.ab.ca/~keeling/emails.html

Re: query-replace-regexp ... "Invalid repacement string '\.'"

[Malte Spiess]

"s. keeling" <keeling@spots.ab.ca> writes:

> Hi.  I was trying to make it easy on myself using q-r-r replacing
> '[^\]\.' (not a backslash, followed by a literal dot/period) with the
> string (sans quotes) '\.', essentially "escaping" every dot/period in
> the file.  "M-x query-replace" had no trouble with it but M-x
> query-replace-regexp refused, spouting the error message in the
> subject.

In a regexp for a "\" you need to escape, so write "\\". "\]" is a
mistake.
A correct regexp for your intention should be
'[^\\]\.'
   --

> So how do you replace '.' with '\.' in emacs?

That should be fine.

> Suggestions or pointers welcome.  Thanks.

HTH

Malte

Re: query-replace-regexp ... "Invalid repacement string '\.'"

[David Kastrup]

[Oops, superseded]

Malte Spiess <i1tnews@arcor.de> writes:

> "s. keeling" <keeling@spots.ab.ca> writes:
>
>> Hi.  I was trying to make it easy on myself using q-r-r replacing
>> '[^\]\.' (not a backslash, followed by a literal dot/period) with the
>> string (sans quotes) '\.', essentially "escaping" every dot/period in
>> the file.  "M-x query-replace" had no trouble with it but M-x
>> query-replace-regexp refused, spouting the error message in the
>> subject.
>
> In a regexp for a "\" you need to escape, so write "\\". "\]" is a
> mistake.

No, it isn't.  Inside of [], \ is not special.

> A correct regexp for your intention should be
> '[^\\]\.'
>    --
>
>> So how do you replace '.' with '\.' in emacs?
>
> That should be fine.

Maybe something like

M-x query-replace-regexp RET \(^\|[^\]\)\. RET \1\\. RET

Or even

M-x query-replace-regexp RET \(\(^\|[^\]\)\(\\\\\)*\)\. RET \1\\. RET

(which considers a dot preceded by an even number of backslashes as
unescaped).

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum

Re: query-replace-regexp ... "Invalid repacement string '\.'"

[Malte Spiess]

David Kastrup <dak@gnu.org> writes:

> Malte Spiess <i1tnews@arcor.de> writes:
>
>> "s. keeling" <keeling@spots.ab.ca> writes:
>>
>>> Hi.  I was trying to make it easy on myself using q-r-r replacing
>>> '[^\]\.' (not a backslash, followed by a literal dot/period) with the
>>> string (sans quotes) '\.', essentially "escaping" every dot/period in
>>> the file.  "M-x query-replace" had no trouble with it but M-x
>>> query-replace-regexp refused, spouting the error message in the
>>> subject.
>>
>> In a regexp for a "\" you need to escape, so write "\\". "\]" is a
>> mistake.
>
> No, it isn't.  Inside of [], \ is not special.

Oh. Oops, sorry. Must admit I never used "\" inside of []. Didn't expect
a change there.

> Maybe something like
>
> M-x query-replace-regexp RET \(^\|[^\]\). RET \1\\. RET
>
> Or even
>
> M-x query-replace-regexp RET \(\(^\|[^\]\)\(\\\\\)*\). RET \1\\. RET
>
> (which considers a dot preceded by an even number of backslashes as
> unescaped).

In case he wants to replace the character before the "." as well (which
I doubt) '\\.' as a replacement string should do fine.

Else the proposed constructions with \(...\) and \1 (sometimes even \2
or \3) should work fine. This is a really useful feature, one should
learn how to use it to simplify lots of replacement tasks.

Greetings

Malte

Re: query-replace-regexp ... "Invalid repacement string '\.'"

[David Kastrup]

"s. keeling" <keeling@spots.ab.ca> writes:

> Hi.  I was trying to make it easy on myself using q-r-r replacing
> '[^\]\.' (not a backslash, followed by a literal dot/period) with the
> string (sans quotes) '\.', essentially "escaping" every dot/period in
> the file.  "M-x query-replace" had no trouble with it but M-x
> query-replace-regexp refused, spouting the error message in the
> subject.
>
> So how do you replace '.' with '\.' in emacs?  Googling's
> (groups.google.com) turned up nothing useful (interesting, but not
> useful).  I tried variations of '\\\.' (literal backslash followed by
> literal period) to no effect.
>
> Suggestions or pointers welcome.  Thanks.

M-x query-replace-regexp RET \. RET \\. RET

. is not special in the replacement string.  You can also write

M-x query-replace-regexp RET \. RET \\\& RET

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum

Re: query-replace-regexp ... "Invalid repacement string '\.'"

[Malte Spiess]

David Kastrup <dak@gnu.org> writes:

> "s. keeling" <keeling@spots.ab.ca> writes:
>
>> Hi.  I was trying to make it easy on myself using q-r-r replacing
>> '[^\]\.' (not a backslash, followed by a literal dot/period) with the
>> string (sans quotes) '\.', essentially "escaping" every dot/period in
>> the file.  "M-x query-replace" had no trouble with it but M-x
>> query-replace-regexp refused, spouting the error message in the
>> subject.
>>
>> So how do you replace '.' with '\.' in emacs?  Googling's
>> (groups.google.com) turned up nothing useful (interesting, but not
>> useful).  I tried variations of '\\\.' (literal backslash followed by
>> literal period) to no effect.
>>
>> Suggestions or pointers welcome.  Thanks.
>
> M-x query-replace-regexp RET \. RET \\. RET

That would not work if there already is a "\" in the text. Your other
proposal is much better IMHO. (I think he does not want "\." to be
replaced with "\\.".)

I guess you just wanted to describe the general concept, this is just to
prevent confusion for other readers.

Greetings

Malte