How templates might be improved

[Chris Wright via Digitalmars-d]

On Sat, 17 Sep 2016 12:02:47 +0000, Stefan Koch wrote:

> On Friday, 16 September 2016 at 23:44:42 UTC, Chris Wright wrote:
> 
> 
>> On the other hand, in a change of behavior, this will be a cache miss
>> and the template is instantiated twice:
>>
>>   alias myint = int;
>>   alias TypeA = Typedef!int;
>>   alias TypeB = Typedef!myint;
> No It would not be a miss the type is the same

Can you give examples that would produce a cache miss?

>> If someone tries implementing the recursive form of the Fibonacci
>> function with your change in place, they'll have unusably long compile
>> times. However, in the typical case,
>> compile times will be faster (and specific types can more easily
>> receive special treatment as needed).
> 
> If someone tries to implement fibobacci as a recursive template ...
> well there is no way that can be fast.
> With interning or without.

If the compiler caches template instantiations, you get the memoized form 
and it can be computed in linear time. If it doesn't, exponential time.