The new, new phobos sneak preview

[Don]

Andrei Alexandrescu wrote:
> Lars Kyllingstad wrote:
>> Michel Fortin wrote:
>>> On 2009-04-12 11:09:51 -0400, Lars Kyllingstad 
>>> <public at kyllingen.NOSPAMnet> said:
>>>
>>>> Andrei Alexandrescu wrote:
>>>>> Lars Kyllingstad wrote:
>>>>>> I think isInfinite!() should be called isInfiniteRange!(). The 
>>>>>> current name is, in my opinion, too general.
>>>>>
>>>>> I'm undecided about this (and similar cases). isInfinite sits 
>>>>> inside std.range, so std.range.isInfinite is clear and 
>>>>> std.range.isInfiniteRange feels redundant. On the other hand, I 
>>>>> don't want to use too common symbols because then the user will be 
>>>>> forced to prefix them whenever they clash.
>>>>
>>>> I'm not too worried about name clashes, I just think it sounds 
>>>> wrong. If R is a range with infinitely many elements, I think it's 
>>>> more correct to say "R is an infinite range" than to say "R is 
>>>> infinite".
>>>>
>>>> As an example of what I mean, let the range R be the sequence 1, 
>>>> 1/4, 1/9, ...:
>>>>
>>>>    alias Sequence!("1/(n*n)", 1) R
>>>>
>>>> Then, isInfiniteRange!(R) should obviously yield true. From a 
>>>> mathematical standpoint, I think the result of isInfinite!(R) is 
>>>> less obvious. Yes, the range has infinitely many elements, but none 
>>>> of them are infinite, nor is their sum infinite.
>>>
>>> Perhaps it should be renamed to isUnbounded then.
>>
>> ...except that my example, and indeed any range produced by sequence, 
>> recurrence, etc. are bounded at one end. Thus the term "infinite 
>> range" is more precise, and fits in well with the mathematical terms 
>> "infinite series" and "infinite sequence". Just not "infinite" alone. :)
>>
>> -Lars
> 
> Finally! I was waiting for someone to make this point. "Bounded" would 
> be closer to "having values within a finite interval".
> 
> Andrei

There's a funny thing with floating-point numbers, though.
The range [real.max, real.infinity] contains only two elements, one of 
which is infinity. Is that an infinite range?

It would be helpful to distinguish "contains arbitrary many 
elements"/"length is undefined" from "contains the point at 
infinity"/"includes the maximum representable element for this type".