OpenEuphoria

Re: New keyword added: continue

• Posted by CChris <christian.cuvier at agric?ltur?.gouv.fr> May 28, 2008
• 783 views

Kat wrote:
> 
> Derek Parnell wrote:
> > 
> > Kat wrote:
> > > }}}
<eucode>
> > > :restart
> > > for loop = 1 to 12 do
> > > :retry
> > >  -- code
> > >  if blah then goto restart end if
> > >  if blorg then goto retry end if
> > >  if not x then goto exit end if
> > >  if CK then goto next end if
> > >  if worstcase then goto cleanup&return end if
> > >  -- code
> > >  :next
> > > end for
> > > :exit
> > > </eucode>
{{{

> > 
> > Hi Kat,
> > just a few of quick questions ...
> > 
> > ** How, as a maintainer of the code above, can I be sure that process flow
> > only
> > gets to the "restart:" label from either the statement immediately preceding
> > it or the 'goto' inside the loop? In other words, how can I be sure that
> > there
> > is not another 'goto restart' elsewhere in the code?
> 
> You can't. You read the code to see if there is another "goto" that label. The
> same with "exit", "return", etc.. I have a fair amount of code that has
> "return"
> sprinkled around, and no one has ever complained about more than one place
> leaving
> the function. One way to restrict the "where from" is to localise all "goto"
> to procedure/function blocks, and not allow it in top level code. Exactly like
> in OOEU.
> 
> > ** If I have to place another looping construct within the same scope as the
> > one above, what should I call the labels?
> 
> Umm, how about "loop2" ? Or you mean the targets for more "goto" of the same
> umm, form? Pick a name. You have the freedom to restart the inner loop, the
> outer loop, the nested while loop in there which you added later, etc.. I tend
> to give my nested loop names some description, even if it's just "index1", so
> i could have a "goto restart_index1", which sorta reads easily, and i know
> just
> where it's going, and i can get there with the one "goto" keyword from any
> depth
> of nested loops. The target being present alerts me, as i am reading down the
> code, that i may be going back to that point from somewhere.
>  
> > ** Under what circumstanes might I have to rename the labels?
> 
> Never, i believe. If you add loops, or other code, you do not need to change
> anything, assuming your intent to goto the :target is the same. If you wish
> to add a target, choose another name. Like i said, i tend to use the loop name
> as part of the target, and/or/as well as the purpose, if i need any
> clairification,
> rather insuring unique target names. This way i can wrap or unwrap nested
> loops,
> and not have a problem, as well as skip blocks during debug.
> 
> With goto scope restricted to proc/funct blocks, it makes some code even
> easier,
> such as "goto cleanup&return", which i know has the local scope of variables,
> is at the bottom of the block where code will fall thru to anyhow, and execute
> the "cleanup&return". With Eu the way it is now, i have hunks of code
> copy/pasted
> thruout which does the cleanup with local vars and returns, and those hunks
> are a nightmare to keep identical. Just as an aside, one other cure for that
> would be nested procedures, which could be called inside the nesting
> procedure,
> and the nested one have the scope of the nesting one's vars, i did this in
> Turbo
> Pascal a *lot*.
> 
> I believe Matt scored 100 with the way he did goto in OOEU, and i reiterate
> my suggestion all of OOEU be merged into Eu v4.
> 
> Kat

Which I'd support, with probably reservations about namespace handling.

CChris