Returning a reference to be manipulated

[Paul Backus]

On Thursday, 13 April 2023 at 07:05:10 UTC, Chris Katko wrote:
> Right now, I'm using pointers which resolves to:
>
> ```D
> // float* opIndex(string key){...} using pointer
> (*s["tacos"])++; // works with pointer, but is strange looking
>
> s["tacos"]++; // preferred syntax or something similar
> ```

You can use a wrapper struct with `alias this` to make the 
pointer a little nicer to use:

```d
struct Ref(T)
{
     T* ptr;
     ref inout(T) deref() inout { return *ptr; }
     alias deref this;
}

Ref!T byRef(T)(ref T obj)
{
     return Ref!T(&obj);
}

struct stats
{
     float[string] data;

     Ref!float opIndex(string key)
     {
         return data.require(key, 0).byRef;
     }
}

void main()
{
     stats foo;
     auto x = foo["tacos"];
     x++;
     assert(foo["tacos"] == 1);
}
```