OpenEuphoria

Re: Good Use of GOTO

• Posted by Kat <KAT12 at co?sahs.?et> Jun 06, 2008
• 836 views

Derek Parnell wrote:
> 
> Kat wrote:
> 
> > I gave code for that also. It involved:
> > goto exit
> > goto retry
> > goto restart
> > goto next
> > goto cleanup&return
> > etc.
> > 
> > The only way that's not clear is if you don't read english.
> 
> For example:
> 
>    ----- fileA.e ----
>    function qwerty( integer b)
>    integer a
>    a = b
>    label start:
>    if a < 10 then
>      a = foo(b)
>      if a < 0 then
>         goto exit  -- Which exit does this go to?
>      end if
>      b = bar(a)
>      goto start    -- which start?
>    end if
>    label exit:
> 
>    label start:
>    a = 5
>    while a < 10 do
>      a = bar(b)
>      if a < 0 then
>         goto exit
>      end if
>      b = foo(a)
>      foto start
>    end if
>    label exit:
> 
>    return a
>    end function
> 
> Oh hang on, all labels in the scope must be unique. So now I have to
> numbering?
> them.
> 
>    function qwerty( integer b)
>    integer a
>    a = b
>    label start:
>    if a < 10 then
>      a = foo(b)
>      if a < 0 then
>         goto exit
>      end if
>      b = bar(a)
>      goto start
>    end if
>    label exit:
> 
>    label start1:
>    a = 5
>    if a < 10 do
>      a = bar(b)
>      if a < 0 then
>         goto exit1
>      end if
>      b = foo(a)
>      goto start1
>    end if
>    label exit1:
> 
>    return a
>    end function
> 
> So now not only do I have more to type and more to read I also have to create
> unique label names. 
> 
> Then we've got this sort of problem....
> 
>    a = b
>    label exit:
>    if a < 10 then
>      a = foo(b)
>      if a < 0 then
>         goto start
>      end if
>      b = bar(a)
>      goto exit
>    end if
>    label start:
> 
> Identical syntax from Euphoria's point of view, but very misleading for humans
> to read. Yes, I know is a silly example but the point is that it is possible
> to use label names that are actually misleading in terms of informing the
> reader
> about the coder's intentions.
> 
> 
> The solution we have chosen is this ...
> 
>    function qwerty( integer b)
>    integer a
>    a = b
> 
>    while a < 10 do
>      a = foo(b)
>      if a < 0 then
>         exit
>      end if
>      b = bar(a)
>    end while
> 
>    a = 5
>    while a < 10 do
>      a = bar(b)
>      if a < 0 then
>         exit
>      end if
>      b = foo(a)
>    end while
> 
>    return a
>    end function
> 
> There is no misleading control flow statements now. They are shorter. They
> inform
> you of the coder's intentions. And this is already in Euphoria 3.1

Yeas, sure if you are going to intentionally screw things up. 
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Kat