Re: query-replace-regexp on a string with '=' sign

[Pankaj Jangid <pankaj@codeisgreat.org>]

Tassilo Horn <tsdh@gnu.org> writes:

> Pankaj Jangid <pankaj@codeisgreat.org> writes:
>
>>>> I have a line like this,
>>>>   HELLO=WORLD
>>>> now I want to downcase the part before the equal (=) sign.
>>>> I am approaching like this
>>>>
>>>>  M-x query-replace-regexp RET \(.+\)= RET \,(downcase \1)= RET
>>>>
>>>> But this doesn't work.
>>>
>>> Where "doesn't work" means "doesn't downcase but keeps HELLO", right?
>>
>> Yes. Suppose I have these lines in a region
>> HELLO=WORLD
>> HELLOXXXXWORLD
>> and if I now execute following sequence,
>> M-x query-replace-regexp RET \(.+\)= RET \,(downcase \1)= RET
>> the output is,
>>
>> hello=WORLD
>> HELLOXXXXWORLD
>
> For me (with emacs -Q on the current master), it stays as it is, i.e.,
> all caps.

Oh this is my mistake. I wanted to point out that only.. It stays caps.

>> but if I execute this,
>> M-x query-replace-regexp RET \(.+\)XXXX RET \,(downcase \1)XXXX RET
>> then the output is,
>>
>> HELLO=WORLD
>> helloXXXXWORLD
>
> I can reproduce that.  I think that's documented on the info page I've
> cited.  When the replacement is all lower- or all uppercase (like
> hello=), `case-replace' has an effect.  But when the replacement is
> mixed-case (like helloXXXX), case will be preserved.
>
>>> Have a look at (info "(emacs) Replacement and Lax Matches") which
>>> explains it.  I think the default `case-replace' value of t is the
>>> problem here.
>>
>> Thanks for pointing me to the right direction. Understood case-replace
>> thing. But the one thing that is still not clear to me is that, why
>> the first command doesn't downcase HELLO in the first line, whereas
>> the second command downcases the HELLO in the second line.
>
> Huh?  You've said the first command does downcase hello in the first
> line although I cannot reproduce that and would not have an explanation
> for that behavior.  If it's actually the same for you, then see my last
> paragraph for the explanation.

Sorry for creating confusion ... again.