Safe Languages :-)

Simon Taylor simon at
Sun Apr 4 18:43:58 CDT 2004

Hi Scott,

> I am writing a module in our Portal which allows the execution of code
> from people we do not trust - students.

Including my 14 year old son, who now has a MyInternet account at school and 
whose code you must not trust under any circumstances ;-)

> The idea is to provide a module that allows languages to be programmed
> with very simple inputs and outputs.
> A simple example is - Enter some Logo Code and the output is a GIF.

Sounds very cool.

> I can use Safe (perldoc Safe) to do perl code with some level of
> safety, but what I am really looking for is better educational
> languages.


> Anyway - Obviously what ever I choose they are mostly limited in that
> they are restricted to general programming with only a very basic input
> and output (at this stage a single line of input and plain text output
> - or generation of a graphic).

My 10c worth is that Safe is a clever package, and it (along with Opcode) will 
let you construct an environment in which only a subset of perl is allowed.
It seems to me that building a mini-language out of an existing language
has to be easier than buiding one from scratch.

Having said that, you could always implement the kind of language you're 
describing with Parse::RecDescent

A third option, what about parrot? I read last week that they now have a 
working tcl interpreter implemented against the parrot machine. You could
target a new mini language like logo at parrot. Perhaps someone is already 
doing this.... 


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+61 3 9568 2005

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