OpenEuphoria

Re: Open Source

• Posted by Matt Lewis <matthewwalkerlewis at gma?l.co?> Oct 19, 2007
• 787 views

Juergen Luethje wrote:
> 
> I do not make it a religion. Please do not put words into my mouth.
> I just say that it's obsolete in high-level languages. This is of
> course only true if a language provides sufficient other possibilities.
> For instance in Euphoria, it would be useful not only to have an 'exit'
> statement, but also the possibility to write something like
> 
>    exit <number of levels>

I've often thought this, too, although that construct worries me.  What
happens if the levels change?  Even if they don't change, it's not trivial 
to figure out the target of that exit.  A label-based exit, OTOH, can be 
very useful, and explicit.

For example, perl allows you to name a block (which could be a while/for/etc)
and to use the next/last operators along with the block name:

http://en.wikipedia.org/wiki/Perl_control_structures

A euphorian implementation might look like:

:mainloop for i = 1 to n do
    ...
    :jloop for j = 1 to m do
        ....
        if foo then 
            exit :mainloop 
        end if
        while foo > 5 do
            ...
            if bar then
               exit :jloop
            end if
            ...
    end for
end for

That keeps the labels firmly associated with their proper loops.  It 
makes the goal very clear, although at the expense of clarity of where
you're going:

for i = 1 to n do
    ...
    for j = 1 to m do
        ....
        if foo then 
            goto :mainloop 
        end if
        while foo > 5 do
            ...
            if bar then
               goto :jloop
            end if
            ...
    end for
    :jloop
end for
:mainloop

I can see benefits to both ways, though I think I would prefer keeping 
them associated with the loop.  It's also how exits work right now.

Matt