color lib

[Nicholas Wilson via Digitalmars-d]

On Sunday, 9 October 2016 at 05:21:32 UTC, Manu wrote:
> On 9 October 2016 at 14:03, Nicholas Wilson via Digitalmars-d 
> <digitalmars-d at puremagic.com> wrote:
>> How far would `r.inBatchesOf!(N)` go in terms of compiler 
>> optimisations
>> (e.g. vectorisation) if N is a power of 2?
>>
>> auto inBatchesOf(size_t N,R)(R r) if(N!=0 &&isInputRange!R &&  
>> hasLength!R)
>> {
>>     struct InBatchesOfN
>>     {
>>         R r;
>>         ElementType!(R)[N] batch;
>>         this(R _r)
>>         {
>>              assert(_r.length % N ==0);// could have overloads 
>> where
>> undefined elements == ElementType!(R).init
>>              r = _r;
>>              foreach( i; 0..N)
>>              {
>>                   batch[i] = r.front;
>>                   r.popFront;
>>              }
>>         }
>>
>>         bool empty() { return r.empty; }
>>         auto front { return batch; }
>>         void popFront()
>>         {
>>              foreach( i; 0..N)
>>              {
>>                   batch[i] = r.front;
>>                   r.popFront;
>>              }
>>         }
>>     }
>>
>>     return InBatchesOfN(r);
>> }
>
> Well the trouble is the lambda that you might give to 'map' 
> won't work anymore. Operators don't work on batches, you need 
> to use a completely different API, and I think that's 
> unfortunate.

How?  All you need is an extra `each` e.g. 
r.inBatchesOf!(8).each!(a =>a[].map!(convertColor!RGBA8))

perhaps define a helper function for it that does each + the 
explicit slice + map, but it certainly doesn't scream completely 
different API to me.