Creating a RedBlackTree

[drug]

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