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# [Haskell](https://www.haskell.org) + [hgl](https://www.codeberg.org/wheatwizard/haskell-golfing-library), 9 bytes

```txt
fe"abipq"
```

[Attempt This Online!](https://ato.pxeger.com/run?1=m708I7E4OzUnZ8FNxczcgvyiEoXC0sSczLTM1BSFgKLUnNKUVC6oRMDS0pI0XYvVabZpqUqJSZkFhUoQkZtKuYmZeQq2Cin5XAoKBUUKKgppOQppCtHqieoKenoK6lXqsRCVCxZAaAA)

This is the obvious solution and it's pretty much unbeatable.
I also tried this solution avoiding the hardcoded string:

### 27 bytes

```txt
('x'>)+fe[7,8,15]<dgs 16<Or
```

* `Or`: convert to character point.
* `dgs 16`: take the digital sum base 16.
* `fe[7,8,15]`: check if it is either 7, 8, or 15.
* `('x'>)`: check the input is also less than `'x'`.

Obviously this approach is nowhere near as short as the obvious approach but it's a little fun. (Anyone want to suggest adding `<x>` to the HTML standard?)

## Reflection

* There is the enduring issue that `fe` is way more useful than `e`. There names should be swapped. This would save a byte in both answers.
* `(+)` as a lifted and exists, and there is a lifted or, but it's way longer. `(*)` should act as a lifted or. Meaning at the very least `Predicate a` should have a `Rig` instance. If this were the case we could do:
  ```txt
  eq 'i'*fe[7,8]<dgs 16<Or
  ```
  Which saves 3 bytes in the long answer.
* There could be hard-coded variants for common digital sums. It's pretty much random chance that the number used here (16) is a power of two, but numbers from 2-11 plus 16, 32, and 64 are probably wise to have.