Why Strings as Classes?

[Robert Fraser]

superdan wrote:
>> No, the SCALABLE opIndex runs in O(1). The CORRECT opIndex can run in 
>> O(n^n) and still be correct.
> 
> stepanov has shown that for composable operations the complexity must be part of the specification. otherwise composition easily leads to high-order polynomial that fail to terminate in reasonable time. opIndex is an indexing operator expected to run in constant time, and algorithms rely on that. so no. opIndex running in o(n^n) is incorrect because it fails it spec.

Um.. . how would one "show" that. I'm not talking theoretical bullshit 
here, I'm talking real-world requirements. Some specs of operations 
(composable or not) list their time/memory complexity. Most do not. 
They're still usable. I agree that a standard library sort routine is 
one that *should* list its time complexity. My internal function for 
enumerating registry keys doesn't need to.

> here you hint you don't understand what i'm talking about indeed. neither of java, c#, or tango define a[n] to run in o(n). they define named functions, which i'm perfectly fine with.

I guess I didn't understand what you were saying because you _never 
mentioned_ you were talking only about opIndex and not other functions. 
I don't see the difference between a[n] and a.get(n); the former is just 
a shorter syntax. The D spec certainly doesn't make any guarantees about 
the time/memory complexity of opIndex; it's up to the implementing class 
to do so. In fact, the D spec makes no time/memory complexity guarantees 
about sort for arbitrary user-defined types, either, so maybe you 
shouldn't use that.

> funny you should mention that. window manager in windows 3.1 worked exactly like that. users noticed that the more windows the opened, the longer it took to open a new window. with new systems and more memory people would have many windows. before long this became a big issue. windows 95 fixed that.
> 
> never misunderestimate scalability.

I don't know enough about GUI programming to say for sure, but that 
suggests a window manager shouldn't be written using linked lists. It 
doesn't suggest that getting a value from an arbitrary index in a linked 
list is useless (in fact, it shows the opposite -- that it works fine -- 
it just shows its not scalable).