A purity change

[Meta]

On Thursday, 11 July 2013 at 16:14:13 UTC, H. S. Teoh wrote:
> On Thu, Jul 11, 2013 at 05:25:09PM +0200, bearophile wrote:
> Hmm. This seems to be a tricky corner case. The delegate itself 
> is impure, as it accesses y which is outside of its definition 
> and isn't part of its arguments; however, in the larger context 
> of spam(), this shouldn't be a problem since y is accessed via 
> 'this', and 'this' is part of spam's input.

Isn't it okay for pure functions to access global immutable 
state, such as what the delegate is doing here?