const sucks

[Don]

Bill Baxter wrote:
> On Mon, Oct 20, 2008 at 5:50 AM, Derek Parnell <derek at psych.ward> wrote:
>> On Sat, 18 Oct 2008 20:36:51 -0700, Walter Bright wrote:
>>
>>> The problem is things like:
>>>
>>>    void foo(int[] a)
>>>    {
>>>      int[] b;
>>>    }
>>>
>>> so a is const, and b is mutable? That's very confusing. It gives the
>>> appearance of D having a lot of wacky and arbitrary semantic rules.
>> I work with the Euphoria language and this has been the case since its
>> begining. No one, from newbie-coder to experienced coders of a number of
>> languages have EVER thought this as weird.
>>
>> In Euphoria, there is NO WAY one can change a function's argument. The
>> caller of a function can have complete confidence that any argument passed
>> will not have its value changed by the function. However, variables local
>> to the function are not immutable.
>>
>> Your fears may need empirical evidence before I would take them seriously.
> 
> Yeh, and on the other side, I remember way back when I was learning C
> as a newbie that I found it was surprising that parameters acted just
> like local variables.  When you think about it, yeh, they are
> basically, but as a newbie the thought never occurred to me that they
> were (or should be) the same thing.

Learning C, I remember being astonished that it was legal to modify a 
parameter. It still feels wrong to me, so I never do it. Even in asm!
They've always felt to me that they are part of the calling function.

> Even now in D what you can do with them is different.  You can only
> have 'in' or 'ref' on parameters, not on local variables.  So I too
> think more evidence is needed that such a change will make code
> confusing.
> 
> --bb