How would you verify wordle boxes in fp-ts? 🟩 🟨 ⬛

[imcotton]

I've been playing around the Wordle related ideas in fp-ts recently, one interesting gotcha I found along the way, is that it actually quite easy to have those colors marked wrong if not looking closely, even the 3Blue1Brown had to release a second video for the correction because of this very issue:

https://www.youtube.com/watch?v=fRed0Xmc2Wg&t=30s

What have you in mind on this matter by using fp-ts? Any thoughts or solutions you'd like to share?

To speed things up, I've made a scaffolding repo with basic setup as well as several test cases ready to be checking against with, by either

or

Lastly, for the sake of both keeping the thread tight and spoiler free (just in case), might consider using the template below to share the long coding blocks:

<details>

<summary><h3>spoiler (click to expand)</h3></summary>

The answer is

```ts
console.log(42)
```

</details>

spoiler (click to expand)

The answer is

console.log(42)

[imcotton]

Here goes my spin:

(click to expand)

The trick is twice traverse needed from State, one pass wouldn't cut it.

I am skipping imports and typing define here, full code in this repo

const exam = (quiz: CharArr, attempt: CharArr): FlagArr => pipe(

    A.zip(quiz, attempt),

    S.traverseReadonlyArrayWithIndex((i, [ q, a ]) => a === q
        ? S.modify(mark(i))
        : S.of<CharArr, string | void>(a)
    ),

    S.chain(S.traverseArray(a => a == null
        ? flag('G')
        : pipe(
            S.gets(flow(
                A.findIndex<string>(s => s === a),
                O.map(i => S.modify(mark(i))),
            )),
            S.chain(O.match(
                () => flag('D'),
                S.apSecond(flag('Y')),
            )),
        )
    )),

    S.evaluate(quiz),

)

const flag = <T> (f: Flag) => S.of<T, Flag>(f)

const update_by = <T> (v: T) => (i: number) => (arr: ReadonlyArray<T>) => pipe(
    arr,
    A.updateAt(i, v),
    O.getOrElse(() => arr),
)

const mark = update_by(Str.empty)