Pure functions in D

[Mosfet]

Josh Szepietowski wrote:
> Walter Bright Wrote:
> 
>> Knud Soerensen wrote:
>>> When are pure functions coming to dmd ?
>> They're about half-implemented. Given the unexpected huge interest in 
>> this, I'll have to bump up the priority!
> 
> Fantastic news! I must reveal that pure functions are the "killer feature" in D2.0 for me, personally.

Don't really understand why this feature is so important while there are 
so many things to achieve.