CTFE Status

[Stefan Koch via Digitalmars-d]

On Monday, 31 October 2016 at 13:29:01 UTC, Stefan Koch wrote:
> Hi Guys, since I got a few complaints about giving minor status 
> updates in the announce group, I am opening this thread.
>
> I will start with giving an overview of what works and what 
> does not work.
>
> Currently the only basic type you can do arithmetic on is int.
> Altough you can compare longs since a few days.
>
> These are the constructs that will work.
>
> - foreach on static arrays strings and range-foreach  (those 
> kinds (0 .. 64)).
> - switches (even deeply nested ones)
> - for and while loops
> - ternary expressions (? :)
> - if and else statements (as long as you don't use && and || )
> - lables and gotos
> - arithmetic expressions as well as post and pre increment and 
> decrement
>
> Constructs that will not work (but are actively worked on)
>
> - assignment to static array cells
> - long ulong arithmetic.
> - function calls
> - dynamic arrays and slices
> - pointers
> - structs
> - && and ||
> - sliceing
>
> Constructs that will not work and are futher down the list.
>
> - classes
> - closures
> - boundschecks
> - asserts
>
> Please note that there will probably be bugs all over the place.
> So even the working features might not be working completely.

I just fixed a really nasty bug  that prevented the following 
code from working in newCTFE.

int computeFib(int n)
{
     int t = 1;
     int result = 0;

     while(n--)
     {
         result = t - result;
         t = t + result;
     }

    return result;
}

static assert(computeFib(12) == 144);

The line result = t - result is the one triggering the bug.
Because newCTFE broke it down like this
result = t;
result -= result;

This was not found by the compilers testsuite!
I guess we should add it.