Posted by Daniel Pitts on 09/30/07 17:12

On Sep 30, 3:47 am, Summercool <Summercooln...@gmail.com> wrote:
> I wonder which language allows you to change an argument's value?
> like:
>
> foo(&a) {
> a = 3
>
> }
>
> n = 1
> print n
>
> foo(n) # passing in n, not &n
> print n
>
> and now n will be 3. I think C++ and PHP can let you do that, using
> their reference (alias) mechanism. And C, Python, and Ruby probably
> won't let you do that. What about Java and Perl?
>
> is there any way to prevent a function from changing the argument's
> value?
>
> isn't "what i pass in, the function can modify it" not a desireable
> behavior if i am NOT passing in the address of my argument? For one
> thing, if we use a module, and call some functions in that module, and
> the module's author made some changes to his code, then we have no way
> of knowing what we pass in could get changed. Of course, if it is in
> Java, Python, and Ruby, and we pass in a reference to object (not C+
> +'s meaning of alias reference), so the object can get changed, but
> that can be expected, vs passing in n, when n = 1. Even when it is
> Ruby, when everything is an object, passing n in when n = 1 won't ever
> make n become 3. Is there a way to prevent it from happening in the
> languages that allows it?

Some would say that in truely good OO design, the state should be
protected by the object (not the constness of the reference to the
object)

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