skaller wrote:
> On Tue, 2006-09-26 at 21:47 +1000, Jonathan Kelly wrote:
>
>> Hi,
>>
>> am I right in deducing there are no arrays in felix, despite the
>> temptingly titled sections in the tute and ref man? I mean the sort of
>> arrays a C/C++ programmer would be thinking of, obviously.
>>
>
> Felix has first class fixed length arrays whose length
> is determined by a compile time constant, exactly
> the kind in this C:
>
> #define n 1000
> struct X { int array[n]; }
>
> It also has C style arrays:
>
> module Carray
> {
> requires cstdlib;
> open C_hack;
>
> fun array_alloc[t]: int -> ptr[t] =
> '(?1*)std::malloc(sizeof(?1)*$1)';
> ....
>
>
> which are unsafe and can't contain Felix heap pointers.
> You can also use STL vector of course, but again
> only for C++ data types or pointer-free Felix ones.
>
> We're working on a fixed length array whose length
> is determined at construction time dynamically,
> called 'varray' in module Varray.
>
> And possibly also a dynamically extensible array
> like STL vector.
>
> The difficulty here is that there are LOTS of different
> options. Some are hard, for example an extensible
> array which moves its storage around: the way STL handles
> this is very inefficient.
It's within a factor of 2 of optimal, no? What do you mean by
"very" inefficient?
> Using mmap/realloc is much faster,
> but C++ does not provide a move or 'relocate' method
> for objects: realloc doesn't work with copy ctor.
>
It seems a fair bet that C++0x will support "move semantics"
which will make std::vector more efficient in the case of objects
which can be cheaply moved but not cheaply copied.
-- James
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