Change representation of dynamic arrays?

[Steven Schveighoffer]

"Walter Bright" wrote
> 2) Doesn't break array.length as rvalue, as this is rewritten by the 
> compiler as (array.end - array.start).

Yes, but checking the length (which is something I do often in my code) now 
becomes an operation rather than a memory load.  So you are swapping a 
performance hit in one place with one in another.

> What does this break?
>
> 1) Passing dynamic arrays to printf as in:
>
> printf("my string is %*.s\n", str);

Absolutely could not care less :)

>
> So, what do you think?

I think this change is unnecessary for iterators, why do we need to change 
the array representation?  An iterator is a pointer in a sequence of values. 
It does not need to know where in the sequence of values it is, so why would 
you represent an iterator with 2 pointers?  If you make the case that it's 
for bounds checking, then you really need 3 pointers to check for reverse 
iterating past the beginning.  I'll also point out that you are now adding 
the cost of copying two values when passing an iterator around instead of 
one pointer, so using pointers will be faster anyways.

Why not have an iterator type, defined as the property of an array, i.e.:

char[].iterator is a type, which is aliased to char *.

Then you could have properties like:

char[].iterator begin() { return ptr}
char[].iterator end() { return ptr + length}

This is very similar to C++, and makes the most sense to me, and provides 
the most speed out of anything.
You could do something similar with AA's, but the type would have to be a 
struct probably.

It wouldn't even pollute the namespace/require keywords because they are 
properties of the arrays themselves.

-Steve