"temporary" templates

[Suleyman]

On Monday, 2 December 2019 at 01:11:57 UTC, Steven Schveighoffer 
wrote:
> On 12/1/19 4:14 PM, Suleyman wrote:
>> On Wednesday, 27 November 2019 at 20:02:52 UTC, Stefan Koch 
>> wrote:
>>> On Wednesday, 27 November 2019 at 16:32:13 UTC, Steven 
>>> Schveighoffer wrote:
>>>> On 11/27/19 11:15 AM, Steven Schveighoffer wrote:
>>>>
>>>> The more I think about it, the more I like the CTFE with 
>>>> Types as first class approach, because then I can use actual 
>>>> mutating code vs. immutable functional approach that is 
>>>> required with templates.
>>>>
>>>> -Steve
>>>
>>> Yes that is the point.
>>> first class types during ctfe allows you to use weak purity 
>>> instead of strong purity!
>>> And therefore makes AST manipulation or introspection much 
>>> more efficient!
>>>
>>> I'll build a tiny POC shortly. The thing that I got stuck 
>>> with last time was the lexer/parser modification that is 
>>> required to flag type arguments to ctfe functions.
>> 
>> The problem with going the path of giving super powers to CTFE 
>> functions is that it creates a division between runtime and 
>> CTFE then we will get functions which only work in CTFE which 
>> may or may not be a good thing.
>
> We already have CTFE-only functions (assert(__ctfe)) Sometimes 
> CTFE is far preferable to using template expansion.
>
> -Steve

Not to this extent though. What we're potentially discussing here 
is functions which have a reusable body like a runnable template. 
For example a CTFE function `bool isSame(alias A, alias B) { 
return __traits(isSame, A, B); }` this is unlike any regular 
function that we have today.