John Carmack on Eclipse performance

[Joseph Rushton Wakeling]

On 05/10/13 01:55, deadalnix wrote:
> D has some really serious flaw when it come to functionnal style.

Really?  That's a shame. :-(

>   - Function aren't first class.
>   - Delegates break type system.
>   - Immutable object have identity issue that wouldn't show up in a functional
> language. It is unsure what the semantic around them is (and if identity must be
> preserved, then functional style is badly impaired).
>   - Many qualifier do start to not make any sense when using functions as
> arguments (inout for instance).
>   - Expect for type qualifier, it is impossible to express return qualification
> depending on the input(s qualification (and see point above, that do not work
> when using first class functions/delegates).
>
> On implementation side, heap allocated values aren't optimized to go on the
> stack, ever. And the GC is unable to take advantage of immutability. Note that
> because everything is immutable in functional programming, both are mandatory if
> you don't want to trash your performances.

How much of this is actually a language problem (I imagine the first-class 
functions and delegate issues are) and how much is to do with implementation?