D2 is really that stable as it is claimed to be?

[Walter Bright]

On 9/22/2013 7:50 AM, Andrej Mitrovic wrote:
> I run into these all the time, and I have to spend half a minute
> scanning left and right trying to figure out where the damn missing
> brace went. Marginal benefit my ass.


I programmed into my editor (MicroEmacs) the F3 command. F3, when sitting on one 
of ()[]{}<> will find the matching character, even if nested. If it is not on 
one of those characters, it finds the next occurrence of that character.

As a bonus, if it is on the # character at the beginning of the line, it will 
find the matching #if, #ifdef, #elif, #else, or #endif :-)

I find it very, very handy.

It's based on an elithp macro written for Emacs back in the 1980's. If your 
editor has any ability to have user-written extensions, this is a simple one, 
and I highly recommend it. Here's the corresponding MicroEmacs implementation:

-----------------------------------------------------------------------
/*********************************
  * Examine line at '.'.
  * Returns:
  *	HASH_xxx
  *	0	anything else
  */

#define HASH_IF		1
#define HASH_ELIF	2
#define HASH_ELSE	3
#define HASH_ENDIF	4

static int ifhash(clp)
LINE *clp;
{
     register int len;
     register int i,h;
     static char *hash[] = {"if","elif","else","endif"};

     len = llength(clp);
     if (len < 3 || lgetc(clp,0) != '#')
	goto ret0;
     for (i = 1; ; i++)
     {
	if (i >= len)
	    goto ret0;
	if (!isspace(lgetc(clp,i)))
	    break;
     }
     for (h = 0; h < arraysize(hash); h++)
	if (len - i >= strlen(hash[h]) &&
	    memcmp(&clp->l_text[i],hash[h],strlen(hash[h])) == 0)
	    return h + 1;
ret0:
     return 0;
}


/*********************************
  * Search for the next occurence of the character at '.'.
  * If character is a (){}[]<>, search for matching bracket.
  * If '.' is on #if, #elif, or #else search for next #elif, #else or #endif.
  * If '.' is on #endif, search backwards for corresponding #if.
  */

int search_paren(f, n)
     {
     register LINE *clp;
     register int cbo;
     register int len;
     register int i;
     char chinc,chdec,ch;
     int count;
     int forward;
     int h;
     static char bracket[][2] = {{'(',')'},{'<','>'},{'[',']'},{'{','}'}};

     clp = curwp->w_dotp;		/* get pointer to current line	*/
     cbo = curwp->w_doto;		/* and offset into that line	*/
     count = 0;

     len = llength(clp);
     if (cbo >= len)
	chinc = '\n';
     else
	chinc = lgetc(clp,cbo);

     if (cbo == 0 && (h = ifhash(clp)) != 0)
     {	forward = h != HASH_ENDIF;
     }
     else
     {
	if (inword())
	{   // Search for word the cursor is currently on
	    int s;
	    do
		s = backchar(FALSE, 1);
	    while (s && inword());

	    if (s && forwchar(FALSE, 1))
	    {
		int start = curwp->w_doto;
		if (word_forw(FALSE, 1))
		{
		    cbo = curwp->w_doto;
		    int i;
		    for (i = 0; i < NPAT - 1 && start + i < cbo; i++)
		    {
			pat[i] = lgetc(clp, start + i);
		    }
		    pat[i] = 0;
		    if (Dsearchagain(f, n))
			return backchar(FALSE, 1);
		}
	    }
	    mlwrite("Not found");
	    return FALSE;
	}
	forward = TRUE;			/* forward			*/
	h = 0;
	chdec = chinc;
	for (i = 0; i < 4; i++)
	    if (bracket[i][0] == chinc)
	    {	chdec = bracket[i][1];
		break;
	    }
	for (i = 0; i < 4; i++)
	    if (bracket[i][1] == chinc)
	    {	chdec = bracket[i][0];
		forward = FALSE;	/* search backwards		*/
		break;
	    }
     }

     while (1)				/* while not end of buffer	*/
     {
	if (forward)
	{
	    if (h || cbo >= len)
	    {
		clp = lforw(clp);
		if (clp == curbp->b_linep)	/* if end of buffer	*/
		    break;
		len = llength(clp);
		cbo = 0;
	    }
	    else
		cbo++;
	}
	else /* backward */
	{
	    if (h || cbo == 0)
             {
		clp = lback(clp);
		if (clp == curbp->b_linep)
		    break;
		len = llength(clp);
		cbo = len;
             }
	    else
		--cbo;
	}

	if (h)
	{   int h2;

	    cbo = 0;
	    h2 = ifhash(clp);
	    if (h2)
	    {	if (h == HASH_ENDIF)
		{
		    if (h2 == HASH_ENDIF)
			count++;
		    else if (h2 == HASH_IF)
		    {	if (count-- == 0)
			    goto found;
		    }
		}
		else
		{   if (h2 == HASH_IF)
			count++;
		    else
		    {	if (count == 0)
			    goto found;
			if (h2 == HASH_ENDIF)
			    count--;
		    }
		}
	    }
	}
	else
	{
	    ch = (cbo < len) ? lgetc(clp,cbo) : '\n';
	    if (eq(ch,chdec))
	    {   if (count-- == 0)
		{
		    /* We've found it	*/
		found:
		    curwp->w_dotp  = clp;
		    curwp->w_doto  = cbo;
		    curwp->w_flag |= WFMOVE;
		    return (TRUE);
		}
	    }
	    else if (eq(ch,chinc))
		count++;
	}
     }
     mlwrite("Not found");
     return (FALSE);
}