On Wednesday, 6 August 2014 at 11:32:41 UTC, Puming wrote:
I found AA initialization have a strange effect:
```d
string[string] map; // same as `string[string] map =
string[string].init;
writeln(map); // output: []
string[string] refer = map; // make a reference
refer["1"] = "2"; // update the reference
writeln(map); // output: []. The reference does not affect the
original.
```
But if I do an assignment first, the reference works:
```d
string[string] map; // same as `string[string] map =
string[string].init;
writeln(map); // output: []
map["1"] = "0";
string[string] refer = map; // make a reference
refer["1"] = "2"; // update the reference
writeln(map); // output: ["1":"2"]. The reference does affect.
```
So if I want an empty AA and want to use a variable to refer to
it later, I have to do this:
```d
string[string] map; // same as `string[string] map =
string[string].init;
map["1"] = "0";
map.remove("1"); // assign and then REMOVE!
writeln(map); // output: []
string[string] refer = map; // make a reference
refer["1"] = "2"; // update the reference
writeln(map); // output: ["1":"2"]. The reference does affect.
```
which looks awkward.
Is it because `string[string].init == null` ? If so, how do I
specify an empty AA which is not null? Neither `[]` or `[:]`
seems to work.
AFAIK there is no easy way to do it. Maybe it would be fine to
add some function to phobos. Something like this:
auto initAA(VT,KT)() {
static struct Entry
{
Entry *next;
size_t hash;
}
static struct Impl
{
Entry*[] buckets;
size_t nodes;
TypeInfo _keyti;
Entry*[4] binit;
@property const(TypeInfo) keyti() const @safe pure nothrow @nogc
{ return _keyti; }
}
static struct AA
{
Impl* impl;
}
VT[KT] aaa;
AA* aa = cast(AA*)&aaa;
if (aa.impl is null)
{ aa.impl = new Impl();
aa.impl.buckets = aa.impl.binit[];
}
aa.impl._keyti = cast() typeid(aaa);
return aaa;
}
Or it would be fine if I could write something like this: auto aa
= new VT[KT]();
