[plt-scheme] Checking that an expression only contains calls to 'valid' functions.

Hi all,

I would like to check that a given scheme expression only contains
calls to "valid" functions (their names are stored in a list). How
would you do this? Do any of you have a better idea than just parsing
the expression, knowing all the scheme stuctures (let, lambda, etc),
and acting differently depending on each structure? Maybe by catching
some errors?

Actually, I would like the user to be able to use the basic functions
from mzscheme and a few others.

Any ideas would be greatly appreciated.

Yours,

-- 
Jean-Pierre Lozi
http://www.lozi.org
mailto:jean-pierre at lozi.org