parallel-letter-frequency: Rewrite tests to use hspec with fail fast.

[rbasso]

• Rewrite tests to use hspec.
• Move hints to HINTS.md.

Related to #211.

[petertseng]

Yup, seems like a faithful translation 👍

I wonder whether some people will now wonder what the Int arg is if they don't read the README. However the status quo before 1eaff79 was that a stub solution didn't exist at all, so things have at least not be made worse.

If there were a concrete solution to be made, it would be maybe name the args: frequency nWorkers texts = undefined

But maybe that will be too prescriptive, if someone wants to write it eta-reduced (I don't know if anyone will)

[petertseng]

Hmm. guess you can never edit a review summary comment. That's interesting. I was going to edit to link to 1eaff79 .

[rbasso]

I wonder whether some people will now wonder what the Int arg is if they don't read the README.

We don't have to save the lazy ones, but I think it is nice to save the users the work of looking at the README.md.

If there were a concrete solution to be made, it would be maybe name the args: frequency nWorkers texts = undefined

Granted! 😁

But maybe that will be too prescriptive, if someone wants to write it eta-reduced (I don't know if anyone will)

I don't see that as a problem, because the stub solution is just a suggestion, and I expect the serious student to rewrite it multiple times. What usually bothers me is that I'm never sure about how to name the variables - workers, n, nWorkers, texts, ts, xs - so I often delegate that choice to the users.

[petertseng]

👍