static map as a type function

Walter Bright newshound2 at
Thu Sep 24 00:44:21 UTC 2020

On 9/23/2020 4:59 PM, Bruce Carneal wrote:
> On Wednesday, 23 September 2020 at 22:36:55 UTC, Walter Bright wrote:
>> The other way to do it is just have the compiler recognize recursive templates 
>> and implement them directly. This would provide the speedup, while not adding 
>> new features or requiring any user code changes - it'll just run faster.
> I see a few reasons to prefer type functions, wherever applicable (they cant do 
> everything):
> 1) type functions admit a simpler/bounded compiler implementation
> 2) type functions admit simpler meta programs and the related
> 3) type functions should be easier to debug, eager rather than lazy/latent 
> compile time errors for one thing
> 4) type functions exhibit better locality than templates
> 5) to achieve type function like simplicity/debuggability with templates you 
> need to rely more heavily on "best practices"

I don't really understand these points.

Using the existing recursive template calls is well-known and well-understood 
functional style programming. It even aesthetically looks and acts like function 
calls, except with a bang (!).

Making existing constructs work better is better than adding an ever-expanding 
list of new constructs.

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