Lazy evaluation

[Peter Alexander]

On 23/11/11 6:05 PM, Jonathan M Davis wrote:
> On Wednesday, November 23, 2011 18:41:46 Timon Gehr wrote:
>> On 11/23/2011 12:53 AM, Jonathan M Davis wrote:
>>> This basic idea was discussed a couple of months back, and it was
>>> determined that it was overly complicated for very little gain.
>>
>> I strongly disagree.
>
> Well, you're free to disagree, but that's essentially what the discussion
> resulted. And glancing at the thread ( http://www.mail-
> archive.com/digitalmars-d at puremagic.com/msg65324.html ), it looks like you
> posted a couple of times in it, so I'd expect you to be at least somewhat
> aware of what was discussed in it. It's nice in theory, but there are a number
> of complications for what most people consider to be a minor gain. And for the
> folks who really don't like transitive const, it doesn't go anywhere near far
> enough, since they want full-on caching with const, not just lazy evaluation,
> which just isn't going to happen.
>
> - Jonathan M Dav

Just to be clear, I don't think anyone has any problem with the 
transitivity of const, but rather the fact that D only offers bitwise 
const and not logical const, and also that D protocols enforce bitwise 
const when only logical const is needed.

Bitwise const is needed for safe concurrency, but only logical const is 
needed for pure functional programming.