'int' is enough for 'length' to migrate code from x86 to x64

[Andrei Alexandrescu via Digitalmars-d]

On 11/20/14 6:20 AM, Ary Borenszweig wrote:
> On 11/20/14, 6:47 AM, Andrei Alexandrescu wrote:
>> On 11/20/14 12:18 AM, Don wrote:
>>> On Wednesday, 19 November 2014 at 17:55:26 UTC, Andrei Alexandrescu
>>> wrote:
>>>> On 11/19/14 6:04 AM, Don wrote:
>>>>> Almost everybody seems to think that unsigned means positive. It does
>>>>> not.
>>>>
>>>> That's an exaggeration. With only a bit of care one can use D's
>>>> unsigned types for positive numbers. Please let's not reduce the
>>>> matter to black and white.
>>>>
>>>> Andrei
>>>
>>> Even in the responses in this thread indicate that about half of the
>>> people here don't understand unsigned.
>>>
>>> "unsigned" means "I want to use modulo 2^^n arithmetic". It does not
>>> mean, "this is an integer which cannot be negative".
>>>
>>> Using modulo 2^^n arithmetic is *weird*. If you are using uint/ulong to
>>> represent a non-negative integer, you are using the incorrect type.
>>>
>>>> "With only a bit of care one can use D's unsigned types for positive
>>>> numbers."
>>>
>>> I do not believe that that statement to be true. I believe that bugs
>>> caused by unsigned calculations are subtle and require an extraordinary
>>> level of diligence. I showed an example at DConf, that I had found in
>>> production code.
>>>
>>> It's particularly challenging in D because of the widespread use of
>>> 'auto':
>>>
>>> auto x = foo();
>>> auto y = bar();
>>> auto z = baz();
>>>
>>> if (x - y > z) { ... }
>>>
>>>
>>> This might be a bug, if one of these functions returns an unsigned
>>> type.  Good luck finding that. Note that if all functions return
>>> unsigned, there isn't even any signed-unsigned mismatch.
>>>
>>> I believe the correct statement, is "With only a bit of care one can use
>>> D's unsigned types for positive numbers and believe that one's code is
>>> correct, even though it contains subtle bugs."
>>
>> Well I'm sorry but I quite disagree. -- Andrei
>>
>
> I don't think disagreeing without a reason (like the one Don gave above)
> is good.

Most of the statements I disagreed with were opinions.

>>> "unsigned" means "I want to use modulo 2^^n arithmetic". It does
>>> not mean, "this is an integer which cannot be negative".

Opinion.

>>> Using modulo 2^^n arithmetic is *weird*.

Opinion.

>>> If you are using
>>> uint/ulong to represent a non-negative integer, you are using the
>>> incorrect type.

Opinion.

>>> I believe that
>>> bugs caused by unsigned calculations are subtle and require an
>>> extraordinary level of diligence.

Opinion (correctly qualified as belief).


Andrei