Implementing Pure Functions

[Don]

bearophile wrote:
> Walter:
> 
>> Thanks to Andrei Alexandrescu, Brad Roberts, David Held, and Bartosz Milewski for their helpful comments and corrections on this post.<
> 
> *pulls Walter's ears* You have forgotten who has found this problem :-)

So have I. It was mentioned at the start of 2008 with respect to pure, 
but the same problem was mentioned with regard to CTFE much earlier, in 
2006 I think. I think Daniel Keep was the first to mention it.