ow Integers Should Work

[Don]

On 07.12.2011 05:11, bcs wrote:
> On 12/05/2011 11:20 PM, Don wrote:
>> On 06.12.2011 05:21, bcs wrote:
>>> On 12/05/2011 08:37 AM, Don wrote:
>>>> On 05.12.2011 14:31, bearophile wrote:
>>>>> Found through Reddit, two blog posts about how integers should behave
>>>>> in system languages (with hardware support):
>>>>>
>>>>> http://blog.regehr.org/archives/641
>>>>> http://blog.regehr.org/archives/642
>>>>>
>>>>> Bye,
>>>>> bearophile
>>>>
>>>> Not very convincing, since he proposes a change to existing
>>>> architectures, and seems completely unaware of the overflow flag.
>>>
>>> I think he's looking at it form the language theory standpoint. As such,
>>> architectures has nothing to do with it (the architectures to be
>>> targeted has yet to be defined at that point)and getting access to the
>>> overflow flag would require exposing it natively in the language.
>>
>> It's not that he hasn't specified an architecture. It's a proposal which
>> does not work on _any_ existing architectures!
>> It's pure fantasy.
>
> Well you can do it on x86. The fact the it doesn't provied hardware
> traps is irrelevant. You might need to add a lot of branches but you can
> get the semantics he is asking for.
>
> That said, there is another interesting (but independent) question of
> can it be done efficiently? You might have a very good question there,
> but that isn't the question regehr is considering.
>
>>
>> And he talks about NaN, when he means infinity. Floating point overflow
>> never results in a NaN.
>
> You have a point there.
>
>> He doesn't seem to know anything about
>> saturating integer arithmetic, which exists in hardware (even x86
>> machines have supported a couple of operations since 1996).
>>
>> Useless.
>
> Again, he's not interested in the hardware implementation, he's only
> interested in the defined semantics of the language, the things you can
> count on regardless of that instruction set you are using. The fact the
> x86 has saturating integer operations is moot because C doesn't have a
> type the end up using them.

He's talking about system languages. A system language has to have a 
close relationship to the architecture.

By contrast, if you don't care about performance, it's easy -- just use 
BigInts for everything. Problem solved.

Looks like I have to put it more bluntly: I don't think he knows what 
he's talking about. (On this particular topic).