isInfinite isInadequate

[monarch_dodra]

On Tuesday, 12 March 2013 at 14:30:00 UTC, Steven Schveighoffer 
wrote:
> On Tue, 12 Mar 2013 06:49:56 -0400, monarch_dodra 
> <monarchdodra at gmail.com> wrote:
>
>> On Tuesday, 12 March 2013 at 10:01:38 UTC, deadalnix wrote:
>>> I want to resurrect that thread. Can someone explains the 
>>> benefices of isInfinite ? I fail to see how it really benefit 
>>> the code.
>>
>> The advantage of "enum empty = false" is that algorithms gain 
>> a great performance boost by optimizing out any "if 
>> (r.empty)". This can be exploited for things like take, or 
>> anything that iterates as a matter of fact. I don't think 
>> anybody will argue that this is a bad approach.
>
> Wouldn't it automatically be optimized out?  I mean if r.empty 
> is an enum, it's like saying if(false)  I would think even with 
> optimizations off, this might be done.
>
> Not that I'm questioning the value of isInfinite (I'm neutral 
> on it), but this is not a benefit.
>
> -Steve

Right, that's what I said. This first paragraph was just about 
enum empty = false.

The actual "isInfinite" discussion comes later.

Another point: isInfinite is useful, if only to propagate 
infiniteness. For example: "1.repeat().map"a * 2"()". If "map" 
didn't know that repeat is infinite, it would simply provide the 
"dumb" empty implementation, and the final range will have lost 
it's infinite trait.