digitalmars.D.learn - AA initialization
- Puming (36/36) Aug 06 2014 I found AA initialization have a strange effect:
- Kozzi11 (35/71) Aug 06 2014 AFAIK there is no easy way to do it. Maybe it would be fine to
- "Marc =?UTF-8?B?U2Now7x0eiI=?= <schuetzm gmx.net> (3/38) Aug 06 2014 `string[string] aa = [];` would be fine, too, but it currently
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.
Aug 06 2014
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]();
Aug 06 2014
On Wednesday, 6 August 2014 at 13:15:27 UTC, Kozzi11 wrote:
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]();
`string[string] aa = [];` would be fine, too, but it currently
doesn't compile.
Aug 06 2014
On Wednesday, 6 August 2014 at 14:38:34 UTC, Marc Schütz wrote:On Wednesday, 6 August 2014 at 13:15:27 UTC, Kozzi11 wrote:Thanks for your clarification (and also in the other thread), so this is an implementation issue for builtin AAs.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]();`string[string] aa = [];` would be fine, too, but it currently doesn't compile.
Aug 06 2014
"Kozzi11" <kozzi11 gmail.com> On Wednesday, 6 August 2014 at 14:40:00 UTC, Puming wrote:Thanks for your clarification (and also in the other thread), so this is an implementation issue for builtin AAs.https://issues.dlang.org/show_bug.cgi?id=10535
Aug 06 2014