Re: [OT] Re: What is the best way to navigate #ifdef and #endif in C program

[Pascal J. Bourguignon]

Fren Zeee <frenzeee@gmail.com> writes:

> On Aug 2, 5:31 pm, "Daniel (Youngwhan)" <breadn...@gmail.com> wrote:
>> Hi,
>>
>> If there is curly brace, it is easy to navigate between them by M-C-f
>> and M-C-b in c-mode.
>>
>> However, I cannot find a way to navigate in like curly brace when it
>> comes to #ifdef, #else, and #endif.
>>
>> For example, if there is a code like this:
>>
>> #ifdef A_DEFINED
>> (...100 lines)
>> #else
>> (... 500 lines)
>> #endif
>>
>> , is there a easy way to move the cursor from #endif to #ifdef or
>> #else and vice versa?
>>
>> Daniel
>
> You might get better luck posting in a C group also.
>
> I use #ifdef ... #endif often also to comment out blocks of code
> during debugging.
>
> My question to CLISP/ELISP/scheme people is

clisp is an implementation, not a language. 

There is a language named Common Lisp, abreviated as CL.  Perhaps you
mean that?



> If there is a wrapper do nothing type function in elisp/clisp/scheme
> which can have the same effect as commenting out.
>
> This is because I dont like to do comment-region/uncomment-region in
> emacs.
>
> These three lispy languages dont seem to have comment block construct
> like C ie /* and */

AFAIK, emacs lisp doesn't have any block comment feature, and I know
no standard way to do block comment in r5rs scheme, but scheme
implementation may provide the same as in Common Lisp, or with a
different syntax.

In Common Lisp you could try to use #| |#, but unfortunately, it is not like C 
/* and */:

int a[]={
/* hello
   /* world
*/
1,2};
// a contains {1,2}.


(let ((a '(
#| hello
   #|  world 
|#
          1 2)))
  a)

is a syntactic error.


You would have to write:

(let ((a '(
#| hello
   #|  world  |#
|#
         1 2)))
  a)
--> (1 2)



However, in Common Lisp, you could implement a reader macro with a
behavior similar to C /* comments */.

This is the reason why there is no point asking whether there is a
feature X in CL.  You can always add any feature to the language,
thanks to its macros or reader macros, and metalinguistic abilities in
general.


-- 
__Pascal Bourguignon__                     http://www.informatimago.com/