Range to Nullable conversion

[Antonio]

On Friday, 10 June 2022 at 18:00:20 UTC, Paul Backus wrote:
> On Friday, 10 June 2022 at 17:22:53 UTC, Antonio wrote:
>> Can this code be written as a **simple** expression?  (without 
>> having to write helper methods).
>
> ```d
> import std.range, std.typecons;
>
> Nullable!(ElementType!R) maybeFront(R)(auto ref R r)
>     if (isInputRange!R)
> {
>     if (r.empty)
>         return typeof(return)();
>     else
>         return nullable(r.front);
> }
>
> unittest
> {
>     int[] a = [1, 2, 3];
>     int[] b;
>
>     assert(a.maybeFront == nullable(1));
>     assert(b.maybeFront.isNull);
> }
> ```

Nice (and simple) helper method.

Thank you Paul