Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!nrl-cmf!mailrus!tut.cis.ohio-state.edu!ut-sally!utah-cs!utah-gr!uplherc!sp7040!wsccs!val
From: val@wsccs.UUCP (Val Kartchner)
Newsgroups: comp.lang.c
Subject: Re: Another "D" idea (Oh no, not again!)
Message-ID: <316@wsccs.UUCP>
Date: 14 Mar 88 14:42:07 GMT
References: <1170@ucsfcca.ucsf.edu>
Lines: 76
Summary: break n;

In article <1170@ucsfcca.ucsf.edu>, rk9005@cca.ucsf.edu (Roland McGrath) writes:
...(Some things deleted)...
> things like "break 2;" (e.g.,
> 	while (x > 0) { while (y != -1) { if (a) break 2; } }
> ), which gets into the named control-loop thing, so these are not just
> the products of my demented mind.  They are the products of the demented
> minds of people who get paid lots of money to think of them.


     I also think that there should be something like "break 'n';" (Where
     'n' is a constant integer.  Variables would be interesting and floats
     highly ambiguous.)  I've often been deep in multiple loops, and wanted
     to get out a few levels.  Most of the time, I have all the loops that I
     want to exit in a subroutine, and just return, but sometimes I can't
     afford the time for the function call and the return.  This same time
     critical restriction is for testing a "flag" variable at EVERY loop
     condition; I can't always afford the time.

     /* THE WAY IT IS NOW */         /* WITH "break 'n'" */
     void function()                 int another()
     {                               {
       while(....)                     do
	 do                            {
	 {                               ...
	   for(...)                      for(...)
	   {                             {
	     ...                           while(....)  /* funtion() */
	     if(...)                         do
	       return;                       {
             ...                               for(...)
           }                                   {
         } while(...);                           ...
     }                                           if(...)
                                                   break 3;
     int another()                               ...
     {                                         }
       do                                    } while(...);
       {                                   ...
	 ...                             }
	 for(...)                      }
	 {                           }
	   function()
           ...
         }
       }
     }


     A similar difficulty could be bypassed in the "switch" statement if
     this were allowed:

     for(flag=TRUE;flag;)              while(TRUE)
     {                                 {
       ...                               ...
       switch(function())                switch(function())
       {                                 {
	 case ...:                         case ...:
	 case ...:                         case ...:
	   ...                               ...
	   break;                            break;
         default:                          default:
	   flag = FALSE:                     break 2;
	   break;                        }
       }                                 ...
       ...                             }
     }


     Remember, I ask this to increase the usability of C (C is my computer
     language of choice), but it must be used with care.  It would tend to
     disabiguize some complex looping structures, but it must not be
     overused as "goto" often is.
-- 
---  /\  ------------ Val Kartchner  {UT@WSC} ---- #include <flamesuit.h> -----
    /\/\  .    /\   | "Those who don't understand VMS are condemmed to reinvent
   /    \/ \/\/  \  |  Unix; those who understand VMS and Unix use VMS."
==/ U i n T e c h \====!ihnp4!utah-cs!utah-gr!uplherc!sp7040!obie!wsccs!val====