Hi all,
How about having the ability to capture the current lexical environment and
use it as an environment for eval? Something like call/cc, but I guess
call/env. In essence, this would make environments useful as first class
objects (perhaps).
(define my-env #f)
(let ((a 0) (b 1) (c 2))
(call/env (lambda (x) (set! my-env x))))
(eval '(begin
(display a) (newline)
(display b) (newline)
(display c) (newline)
(display my-env) (newline))
my-env)
>> prints:
0
1
2
#<environment 0xDEADBEEF>
Perhaps an unlet would also be useful. This would create a lexical
environment in which several variables were unbound.
(unlet (eval read load)
(call/env (lambda (x) (set! my-env x))))
(eval '(eval '(+ 1 2)) my-env)
=>
#error
Hmmm, perhaps this idea (unlet) couldn't work in any kind of a sensible,
simple, lexical scoping system. Maybe unlet could just set the variables
given to it to #<unspecified> or #f or something.
So, which extant language feature have I overlooked that provides more or
less exactly this? :)
Regards,
Jon
Mildred wrote:
Hi,
I'm new to this mailing list and also new to the scheme language ...
I'm used to Lua but I try to search about functionnal programming, and
I found scheme. It looks like a good language but before using it in my
projects I would like to know if tere is an easy way to create
sandboxes.
In lua, it is easy, you create a table containing functions ... and the
table can be made environment for a function. So, you can easily create
secure sandboxes by loading lua code from file and changing the
environment of the loaded code.
I do not know how to do that in scheme. Apparetly the function
null-environment can return an environment and eval can evaluate some
code in an environment. But the question is how to define a variable in
an environment and also how to undefine a variable that you don't want
to appear.
I didn't found anything about modifying an environment. Is it
possible ? If not, why not ? and is it possible to create sandboxes ?
Thanks
Mildred
_______________________________________________
Guile-user mailing list
Guile-user@gnu.org
http://lists.gnu.org/mailman/listinfo/guile-user
