passing by refference

[Joshua Marshall]

Fredrik Lundh <fredrik at pythonware.com> wrote:
...
> did you read reference 1?

>     http://www.cs.berkeley.edu/~jcondit/pl-prelim/liskov77clu.pdf

<snip>

> replace "CLU" with "Python", "record" with "instance", and "procedure"
> with "function or method", and you get a pretty accurate description
> of Python's object model.

> if you don't agree, please tell us what Python does differently.  be very
> specific.

Yes, I agree this is an accurate description of Python.  CLU function
invocation seems to have call-by-value semantics as well (by my
definition and, I believe, the standard definition).  And like python,
values are object references.

>From "A History of CLU":

  In fact, CLU procedures do not share variables at all.  In addition
  to there being no free variables, there is no call-by-reference.
  Instead arguments are passed "by object"; the (pointer to the) object
  resulting from evaluating the actual argument expression is assigned
  to the formal.  (Thus passing a parameter is just doing an assignment
  to the formal.)

This exactly describes call-by-values, where the values are object
references.  A few lines further down:

  A CLU procedure can have side effects only if the argument objects
  can be modified (since it cannot access the caller's variables).

That is the objects /themselves/, not the l-values holding references
to them.  I don't think we disagree about semantics, only terminology.
I don't think we'll make further progress here.