Re: Scripting Language for FreeCiv

[Maciej Stachowiak <mstachow@alum.mit.edu>]

Schaefer Frank R wrote:
> 
> Hello.
> 
> I'm actually doing some work to get a scripting language to run for
> FreeCiv, a GNU Clone of the strategy game civilisation. People like Guile
> too much, so it's perhaps the best choice. My problem with guile:

Is the scripting language intended to design new games with, or to
construct new AIs, or what?
 
> 1) How can I access the symbol table ? My idea was to provide the user
> with a list of actual cities,  military units or isles for example. I
> think it would be the best if I write them directly into the symbol table.
> Parsing strings to get them in there might be \_much_/ too slow.

You can define variables from the C level. However, I do not reccomend
this approach. Instead, I would reccomend defining procedures that return
a list of cities, look up a city by name, etc.
 
> I'm _not_ the guile freak, so please forgive me two stupid questions:
> 2) Can I make data structures read only, so that changes can only be
>    made from the C-world ?
> 

You can create your own C-implemented first-class types, called `smobs'. If 
you provide only read operations for them, 

> 3) Is there a way to prevent people from peeking and poking arround with
>    guile to brake into a network for ex. ? I mean can I restrict the
>    instruction set / the functions that guile provides ? It should not
>    be possible for example that hackers can use a FreeCiv connection
>    to get the '/etc/password' file or sniffle the tcp-network or fork
>    billions of mini-processes that wipe out all other processes.

You mean you want people to be able to upload untrusted Guile code into
the server? That's probably not a good idea just yet. However, with
some of the upcoming module system changes planned, it should not be
hard to create a "safe" module that provides no dangerous operations,
in which uploaded code should be run. I would consider instead the
approach of running the script code on the client, if that works for your
purposes.

 - Maciej