Re: Non Local Exits: Some usage notes

[Mark Hamburg <mhamburg@...>]

Nice notes on the usage of non-local exits. I should go back and re-read
more of the Dylan material sometime.

I will note that the big win in general is using finally to provide an
approach to writing wrappers that doesn't hurt one's head. Contrast:


    function do_with_lock( lock, fn, ... )
        lock:lock()
        return fn( ... )
    finally
        lock:unlock()
    end

(Blocks elided here.)

With what one has to write today:

    function pcall2call( success, ... )
        if success then
            return ...
        else
            error( ..., 0 )
        end
    end

    function unlocker( lock, ... )
        lock:unlock()
        return pcall2call( ... )
    end

    function do_with_lock( lock, fn, ... )
        lock:lock()
        return unlocker( lock, pcall( fn, ... ) ) )
    end

Mark