static map as a type function

[Stefan Koch]

On Thursday, 24 September 2020 at 15:34:06 UTC, H. S. Teoh wrote:

> what I had in mind was what Walter said about leveraging the 
> existing language instead of adding new features.  My thought 
> was to introduce new syntax that maps to the current template 
> implementation (recursion, etc.):

That means changing the langauge.

> new syntax won't significantly add to the weight of the 
> language since you're not defining new semantics.  This solves 
> the writability / readability problem.

It's debatable of that won't add to the weight of the language.

>  Then the next step is to improve the implementation, so that 
> it benefits both existing template code and, by extension, the 
> new syntax. This would solve the performance issue, or at least 
> address it.

Sure, if there is any theoretically sound way to extract a 
monomorphic iterative form out of a polymorphic recursion in O(1).
And when you have found it you _just_ have to implement it, 
correctly.

> Or maybe a more sensible approach is to implement a template 
> optimizer with the current language, that optimizes certain 
> patterns into iterative code, then at a later point introduce 
> primitives that let you access this iterative code directly.

So you are saying first introduce type functions to be used under 
the hood an later on make them available?