[Issue 1475] allow to use intrinsic math functions (e.g. trigonometry) in CTFEs

[BCS]

Sean Kelly wrote:
> d-bugmail at puremagic.com wrote:
> 
>>
>> ------- Comment #2 from wbaxter at gmail.com  2007-09-05 16:10 -------
>> Of course you can already do this by writing your own CTFE functions to
>> approximate those via Taylor series and the like.  One of the first 
>> CTFE demos
>> was a compile-time sqrt function.
>>
>> But yeh, the compiler has access to a better way to evaluate those 
>> functions
>> than running what amounts to an interpreted language, so it would be 
>> nice to be
>> able to access it.
> 
> 
> It was my impression that CTFE relies on a fancy version of constant 
> folding, which doesn't make support for any special routines or plugins 
> a really natural fit.  And while it seems like a potentially interesting 
> feature to add, I wonder whether there might be issues related to cross 
> compilation.

Intrinsics are just function that get special handling. Something akin 
to that could be done for CTFE. Put some special case rules in the 
engine for sin/cos/tan/etc. that call functions that are part of the 
compiler.