Re: Creating a RedBlackTree
On 15.05.2019 16:08, Bogdan wrote:
I don't have any experience with using templates. Is it possible to
create a RB tree containing structs, where the nodes are ordered by one
struct member?
```
import std.stdio;
import std.container;
enum KeyID: uint
{
KEY_A,
KEY_S,
KEY_D,
KEY_W
}
struct KeyController
{
KeyID ID;
bool isDown;
}
void main()
{
auto rbt = redBlackTree!KeyController;
}
```
When I run this I get a compile error:
```
Error: template instance
`std.container.rbtree.RedBlackTree!(KeyController)` does not match
template declaration RedBlackTree(T, alias less = "a < b", bool
allowDuplicates = false) if (is(typeof(binaryFun!less(T.init, T.init
```
You can use predicate for this purpose:
```
auto rbt = redBlackTree!((a, b) => a.ID < b.ID, KeyController);
```
https://run.dlang.io/is/CNRTQf
Re: Creating a RedBlackTree
On Wednesday, 15 May 2019 at 13:08:18 UTC, Bogdan wrote:
I don't have any experience with using templates. Is it
possible to create a RB tree containing structs, where the
nodes are ordered by one struct member?
```
import std.stdio;
import std.container;
enum KeyID: uint
{
KEY_A,
KEY_S,
KEY_D,
KEY_W
}
struct KeyController
{
KeyID ID;
bool isDown;
}
void main()
{
auto rbt = redBlackTree!KeyController;
}
```
When I run this I get a compile error:
```
Error: template instance
`std.container.rbtree.RedBlackTree!(KeyController)` does not
match template declaration RedBlackTree(T, alias less = "a <
b", bool allowDuplicates = false) if
(is(typeof(binaryFun!less(T.init, T.init
```
Key controller cannot be compared by less
which is why it fails, give it an opCmp and it'll work.
Re: Creating a RedBlackTree
On Wednesday, 15 May 2019 at 13:15:50 UTC, Stefan Koch wrote:
Key controller cannot be compared by less
which is why it fails, give it an opCmp and it'll work.
Works fine, thank you! For some reason, I thought that this
template uses references:
```
enum KeyID: uint
{
KEY_A,
KEY_S,
KEY_D,
KEY_W
}
struct KeyController
{
KeyID ID;
bool isDown;
int opCmp(ref const KeyController other) const {return this.ID -
other.ID;}
}
void main()
{
KeyController[] monitoredKeys = [{KeyID.KEY_A}];
auto rbt = redBlackTree!KeyController;
rbt.insert(monitoredKeys);
writeln(rbt);
monitoredKeys[0].isDown = true;
writeln(rbt);
}
```
Output:
```
RedBlackTree([const(KeyController)(KEY_A, false)])
RedBlackTree([const(KeyController)(KEY_A, false)])
```
Re: Creating a RedBlackTree
On Wednesday, 15 May 2019 at 13:19:36 UTC, drug wrote: You can use predicate for this purpose: ``` auto rbt = redBlackTree!((a, b) => a.ID < b.ID, KeyController); ``` https://run.dlang.io/is/CNRTQf Even better, thank you!
