Re: Exit chunk

[Rici Lake <lua@...>]

The simplest way to do that is with error; you can catch the errors 
with pcall.

> do local exit = {};
>>   function breakscript(x) if x then error(exit) end end
>>   function doscript(chunk)
>>     local ok, err = pcall(chunk)
>>     if not ok and err ~= exit then error(err, 0) end
>>   end
>> end
> function X(str) local chunk = assert(loadstring(str, "in")); return 
doscript(chunk) end
>
> X [[ print "hello"; breakscript(); print "world"]]
hello
world
>
> X [[ print "hello"; breakscript(1); print "world"]]
hello

-- Note that it does not affect normal error handling

> X [[ print(a.foo); breakscript(1); print "world"]]
[string "in"]:1: attempt to index global `a' (a nil value)
stack traceback:
        [C]: in function `error'
        stdin:5: in function `doscript'
        (tail call): ?
        stdin:1: in main chunk
        [C]: ?

On 20-Oct-04, at 4:49 PM, Brett Kapilik wrote:

> Hi,
>
> I know that this has been addressed before, but I can't find it for 
> the life of me.  My question is:
>
> Is there an integrated way (or even a hack) to halt the execution of a 
> Lua chunk.  What I would like is something like:
>
> print ("hello");
> breakfromscript;
> print ("world");
>
> would produce:
>
> hello
>
> That is, the fictional "breakfromscript" call would stop excution of 
> the current script (from pcall).  Kind of like doing a return from a 
> function.
>
> This would be really helpful as a way to short circuit script 
> executions in lengthy scripts.  I know that there are all sorts of 
> "good" ways to do this like using if.. else and using functions, but 
> it wouldbe helpful to our customers if there was a way to just tell 
> the Lua engine to simply stop executing the current script chunk.
>
> I am even willing to put a small hack into the Lua engine source code 
> if one exists.
>
> Thanks!
>
> - Brett