passing by refference

[Fredrik Lundh]

Doug Quale wrote:

> According to Joshua, me and R5RS.  R5RS says
>
> "When the procedure is later called with some actual
> arguments, the environment in which the lambda expression was evaluated will
> be extended by binding the variables in the formal argument list to
> fresh locations, the corresponding actual argument values will be stored
> in those locations, and the expressions in the body of the lambda expression
> will be evaluated sequentially in the extended environment."
>
> That's call-by-value by definition.

but that's not how Python works.

in Python, the variables in the formal argument list are bound to the
actual argument objects.  the objects are _shared_ between caller
and callee; there are no "fresh locations" or extra "stores" involved.

(which, of course, is why the CLU folks called this mechanism "call-
by-sharing".  and they were real computer scientists, working for a
real computer science laboratory ;-)

and btw, Python functions doesn't run in an extended environment,
either.  function bodies have very limited access to the surrounding
environment.  but that's another story.

</F>