🚀 go-pugleaf

Andrew Dunbar (andrewd@agnus.livewire.com.au) wrote:
:
: Has anyone thought of the possibility of 'named' loops?
:
: for outer (x = 0; x < MAXX; x++)
: {
:    for inner (y = 0; y < MAXY; y++)
:    {
:       if (map[y][x] == '*')
:          break (outer);
:    }
: }

In article <DHJBHK.ILu@kroete2.freinet.de> erik@kroete2.freinet.de (Erik Corry) writes:
> Definitely better than break(2) or continue(2), but why not do it the
> same way Java does it:
> 
> outer:
> for (x = 0; x < MAXX; x++)
> {
>    for (y = 0; y < MAXY; y++)
>    {
>       if (map[y][x] == '*')
>          break outer;
>    }
> }
> 
> It would be a pity to do it differently to Java unless there's
> a good reason. Of course the question is, what do we gain by this?
> You could trivially do the same with goto. It makes more sense
> for continue, actually, which couldn't be done as well with
> goto. But it is utterly unrealistic to talk about removing
> goto from C9X. Java is in a different situation because it
> doesn't have goto in the first place. One of the benefits of
> an almost clean slate design.

I think that Andrew's `named' loops is the best alternative to this
problem that I'v seen so far! The main reason for this is that the
`label' is so closely coupled to the loop constructor.

I'm not that good at Java but as I understand it `goto' is a reserverd
(but not currently used) keyword. So what happens if goto will become
a legal (and used) keyword? Should it be legal to jump to the `outer:'
label by using a goto from any place in the function? It sure looks
like a valid goto label so why not! Suddenly this is not longer a
"clean slate design" to solve the multi-level break problem.

Needlessly to say; I'm heavily against explicit stated break-levels like:

   for (x = 0; x < MAXX; x++) {
      for (y = 0; y < MAXY; y++) {
   	 if (map[y][x] == '*')
   	    break 2;
      }
   }
   /* The program will continue here after the `break 2;' statement. */
   
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| Fredrik Bredberg          |                                                |
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