iterators again

[David B. Held]

Sean Kelly wrote:
> [...]
> Personally, when writing libraries if I discover that feature X would 
> really simplify things then I'll post an abstract argument on the topic. 
>  I think this is generally a better way to do things because it 
> separates the discussion from any particular use case and allows the 
> feature to be evaluated on its own terms.  That said, those posts have 
> often gone completely unanswered so perhaps I'm going about it the wrong 
> way.
> [...]

The problem with talking about features abstractly is that it's hard to 
judge how necessary or compelling the feature is without the context of 
real examples.  Motivating use cases give hints as to whether the 
feature will only be used in obscure code, whether the feature could be 
easily simulated with an alternative, or whether it's something that you 
could imagine lots of other people running into.  So even though 
academically, it is better to reason about things abstractly, compiler 
design is not an academic pursuit; it's an engineering one.  And 
engineers are better off seeing how a bridge sways in the wind or under 
the feet of pedestrians than modeling it and theorizing about its 
properties abstractly.  When they stick with the abstract, they are 
often surprised by the details of reality.

Dave