Re: Feature request: enhanced break

[Patrick Donnelly <batrick@...>]

On Mon, Nov 24, 2014 at 2:26 AM, Dirk Laurie <dirk.laurie@gmail.com> wrote:
> 2014-11-24 8:54 GMT+02:00 Oliver Kroth <oliver.kroth@nec-i.de>:
>
>> how do you want to pick up the value break provided?
>
> That would be hard if an expression is allowed, which is why I am
> asking for a numeric constant. At present, the compiler generates
> an invisible label "break" and actually does `goto break`. For the
> extension, it would generate an invisible label that cannot be a
> Name, e.g. `break.2`.

This got me thinking about what if the compiler made implicit labels,
e.g. "__break2". I've created an example below with them explicitly
marked:

do
    -- loop 1
    for ... do
        if ... then
            do
                -- loop 2
                for ... do
                    if ... then
                        goto __break2
                    end
                    do
                        -- loop 3
                        for ... do
                            ::__continue1:: -- loop 3 continues loop 3
                        end
                        ::__break1:: -- loop 3 breaks out of loop 3
                    end
                end
                if ... then
                    goto __break2 -- **** Doesn't work! ****
                end
                ::__break1:: -- loop 2 breaks out of loop 2
                ::__break2:: -- loop 3 breaks out of loop 2 and 3
            end
        end
        ::__continue1:: -- loop 1 continues loop 1
        ::__continue2:: -- loop 2 continues loop 1
        ::__continue3:: -- loop 3 continues loop 1
    end
    ::__break1:: -- loop 1 breaks out of loop 1
    ::__break2:: -- loop 2 breaks out of loop 1 and 2
    ::__break3:: -- loop 3 breaks out of loop 1, 2, and 3
end


Alas, this does not work (at least, not without extra effort on the
compiler). I've marked above where it fails.

-- 
Patrick Donnelly