Re: Access Lua's last evaluated result from C

["steve donovan" <steve.j.donovan@...>]

The form of the chunk you actually send to Lua would be 'return
param2*1.5', and gets compiled to a function which returns the value.
You would of course have to insert the values for 'param2' etc into
the global table directly.

steve d.

On Wed, May 14, 2008 at 10:38 AM, Maggie Webb and Pete Kerr
<magnpete@activ8.net.au> wrote:
> Hi
>
> Is there a clean way I can access, from C, the last value computed by Lua,
> if it wasn't assigned to a variable?
>
> Here's why I want to do it:
>
> My C application requires the user to specify parameter values in a file
> like this
>
> param1    3.5
> param2     -0.4
>
> I want to extend this by allowing the user to replace the explicit value
> with some Lua code between dollar signs
>
> param3   $ param2*1.5 $
>
> If I send this chunk to Lua, how do I get the value back? If it was MATLAB,
> say, I'd just fetch the value of variable ans, which always holds the last
> value computed.
>
> I could concatenate "param3=" with "param2*1.5" and fetch the value of
> param3, but in more complex examples the user might submit a list of
> statements with the last one evaluating to the required parameter value.
> e.g.
>
> param3    $  lots of code ;  required_value $
>
> I could of course insist on:
>
> param3    $  lots of code ; param3 = required_value $
>
> Which gives me the easy to read (by a human) list of parameter names down
> the left, but forces the user to type param3 twice, which somehow seems
> inelegant in the context of the already defined syntax for constant values.
>
> Anyway, in another part of the input file, the user supplies simple values
> without a name, where the requirement to supply one would be even more
> clunky.
>
> Thanks,
>
> Pete Kerr
>
>
>