Update words.x

[PiotrJustyna]

A simple comment update to bring it up to date.

Additionally, I changed the function's return type from () to String as it's easier on the eye while executing the lexer.

If this is useful to anybody, here's a link to a sandbox repository I created for alex: https://github.com/PiotrJustyna/alex-sandbox

[andreasabel]

Thanks for the suggestion.

I am not sure about this PR, not a strict improvement...

[andreasabel]

It seems like this was intended as a performance test, running on a large collection of words.
Agreed, the instructions are not portable, e.g. /usr/dict/words does not exist on macOS.
However, the intention can be reconstructed from the comment.

The new comment loses the intention of this example.

[PiotrJustyna]

Thanks for the response.

I see, I didn't realize that those words come with the os. I did some research and did find them on my macos under /usr/share/dict/words but I use haskell primary in an alpine container and those words do not ship with the os by default. They are available though as a package: https://pkgs.alpinelinux.org/packages?name=words&branch=edge&repo=&arch=&origin=&flagged=&maintainer= and when installed, are available here: /usr/share/dict/british-english (there are many languages there).

I'm happy to revert my changes not to affect the intended use of the example (performance test), but probably a descriptive comment and basic instructions how to execute such test would make sense? I feel it would be quite beneficial for those new to alex like myself.

What do you think?

[andreasabel]

Ah, thanks for finding /usr/share/dict/words; it would be good to add this to the existing comment.

but probably a descriptive comment and basic instructions how to execute such test would make sense?

Yes, I agree.
Maybe you can make a longer comment at the beginning of words.x that

• explains its purpose as a benchmark and points to /usr{/share}/dict/words
• explains how to run it in ghci (the thing you wanted to contribute)

I would also think that the "word" <> prefixing would be better removed, just returning the list of lexed strings.

[PiotrJustyna]

Thanks, let me get started on that comment - I feel it would add a lot of value.

You're right - since this is intended to be a performance test, adding the "word: " <> feels unnecessary. Strings feel like a good return type.

[andreasabel]

FYI: benchmark run:

time ./words.bin +RTS -s < /usr/share/dict/words
235976
   1,749,384,800 bytes allocated in the heap
      10,807,296 bytes copied during GC
          62,848 bytes maximum residency (2 sample(s))
          35,456 bytes maximum slop
               6 MiB total memory in use (0 MiB lost due to fragmentation)

                                     Tot time (elapsed)  Avg pause  Max pause
  Gen  0       418 colls,     0 par    0.004s   0.004s     0.0000s    0.0001s
  Gen  1         2 colls,     0 par    0.000s   0.001s     0.0006s    0.0012s

  INIT    time    0.004s  (  0.004s elapsed)
  MUT     time    0.204s  (  0.203s elapsed)
  GC      time    0.004s  (  0.005s elapsed)
  EXIT    time    0.000s  (  0.012s elapsed)
  Total   time    0.212s  (  0.224s elapsed)

  %GC     time       0.0%  (0.0% elapsed)

  Alloc rate    8,577,728,309 bytes per MUT second

  Productivity  96.2% of total user, 90.7% of total elapsed

0.21s user 0.02s system 47% cpu 0.487 total

The benchmark run isn't affected noticeably by the changes in this PR.

[PiotrJustyna]

Comment done. Feels like we could use a more general guide on how to get started with alex, but that's maybe for another day. Thanks for reviewing again.