Re: Load Compiled Script?

["Jim Jones" <jjones@...>]

I think you're right on this one.  It does make sense to allow the user to
place definitions outside the scope of their event functions.

Thanks to everyone for input on this and to Wim's hard work coding.

Jim

----- Original Message -----
From: <RLake@oxfam.org.uk>
To: "Multiple recipients of list" <lua-l@tecgraf.puc-rio.br>
Sent: Wednesday, April 30, 2003 10:27 AM
Subject: Re: Load Compiled Script?


>
> Jim Jones escribió:
>
> -- I want to make definitions, such as the following,
> -- illegal within my system;
> -- All code needs to be contained within function definitions.
> x = 5
>
>
> Why make it illegal? It seems to me to make perfect sense.
>
> If I were scripting in your system, I might well want to throw
> some definitions into the beginning of the script file which
> could be used by my functions. In fact, the power of Lua as
> a configuration language derives exactly from the ability of
> the configurer to execute and not just write configuration files.
>
> The key is that you don't want those definitions to pollute
> the global environment in which your system is running, and
> furthermore you want certain globals to be visible to the
> script files (along with the globals defined in the script
> file). So you need to load and execute the script within
> a specific environment. In Lua 5, I think (Wim will no doubt
> correct me if this isn't right: I'm in a slightly different
> mindset with respect to global environments) you should be
> able to do this as follows:
>
> their_definitions = loadfile "somefile.lua"
> their_env = {
>   math = math, -- give them the math library
>   _STATVERSION = "2.3", -- tell them which version they're in
>   -- etc.
> }
>
> -- Note: rather than adding math as a table to the scripting
> -- environment you present, you might want to give them the
> -- functions as (apparent) globals. But you don't want to
> -- copy raw functions into their environment or the for
> -- statement (below) will fail. So use an __index metamethod
> -- instead: this could easily be generalised to handle more
> -- than one library package:
>
> setmetatable(their_env, {__index = math})
> -- or
> setmetatable(their_env, {
>   __index = function(t, k)
>   return my_utils[k] or math[k] or table[k] or string[k]
> })
>
> setfenv(their_definitions, their_env)
>
> their_definitions() -- now run their script.
>
> for k, v in their_env do
>   if type(v) == "function" then
>     add_to_function_menu(k)
>   end
> end
>
> -- could be generalised to take arguments and return results
> function run_their(function)
>   their_env[function]()
> end
>
> -- ...
>
> run_their "initialise"
> -- do some statistics
> run_their(menu_config.summary_function)
>
> -- etc.
>
>
>
>