On 14.11.2012 20:15, Rainer Schuetze wrote:
On 11/14/2012 7:20 PM, Dmitry Olshansky wrote:
11/14/2012 9:44 PM, Andrei Alexandrescu пишет:
This is new! What does this mean?
I'm sure it is nothing new. Basically AA is a reference type but it is
auto-magically created on the first insertion. This is called magic null
behavior.
void foo(int[int] aa){
//aa here is null
aa[1] = 1;
//now the local aa points to a new hash-map
}
void main(){
int[int] map;
foo(map);
//map in this scope is still null
assert(1 in map); // fails
}
I'm in favor of implicitly allocating an AA on definition that'll make
it a proper reference type.
I don't like the "magic null behaviour", but I see issues with this
straight forward implementation: how can you define a statically
initialized struct value (including init) that contains an associative
array? It will have to run a default constructor to allocate the AA root
object, introducing something like the often rejected user-defined
default constructor for structs.
It doesn't need to allocate any keys or values. It just needs to
allocate whatever structure it needs to keep track of how many items it
has. As if you added an element, and then removed it.
