Use case: eliminate hidden allocations in buildPath

[Michel Fortin]

On 2013-12-05 16:46:52 +0000, Andrei Alexandrescu 
<SeeWebsiteForEmail at erdani.org> said:

> On 12/5/13 8:19 AM, monarch_dodra wrote:
>> Output range! :)
>> 
>> Output range interface makes no linearity requirements. Just that:
>> "out.put(this)" compiles.
> 
> Hrm, construction of a hash table is linearizable so bad example on my 
> part. But I'm talking about general structured data such as objects 
> with allocated fields and connections to other objects etc. etc.

You have to admit that a "bump the pointer" allocator is pretty much 
the same thing as an output range that fills a preexisting array.

So here's an interesting idea: perhaps typed allocators should *be* 
output ranges. The difference is that if you "put" something on the 
allocator, it copies/moves it to the allocator's heap and returns you a 
pointer. While if you "put" something on a generic output range, don't 
expect any pointer out of it.

Some functions, like buildPath, would only require an output range. 
Others will need a more complete allocator, that's those functions that 
want to refer back to elements they've "put" on the allocator's heap.

-- 
Michel Fortin
michel.fortin at michelf.ca
http://michelf.ca