Re: Creating a RedBlackTree

[Stefan Koch via Digitalmars-d-learn]

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.