erlang:is_pure(M,F,Arity)

[Ulf Wiger]

Just a thought...

I was thinking about hacking the shell implementation so that one
could connect to an erlang node via telnet. Part of the fun would
be to filter the function calls so that only a restricted set of
functions could be called.

However, there are lots of functions (like lists:reverse/1, to
name one) that are useful, but totally harmless (... well, in
some sense, anyway).

It struck me that most pure functions could probably be allowed -
and it also struck me that the compiler could probably figure out
if a function's purity can be guaranteed (= it does not call
functions in other modules, or use any built-in functions that
have side-effects).

If that would happen to include a few functions that one would
not make accessible in a restricted shell (perhaps
process_info/[1,2] is one example), then it would at least reduce
the amount of functions that would have to be explicitly
disallowed.

What say ye?

/Uffe
-- 
Ulf Wiger, Senior Specialist,
   / / /   Architecture & Design of Carrier-Class Software
  / / /    Strategic Product & System Management
 / / /     Ericsson Telecom AB, ATM Multiservice Networks