[racket-users] Slack link! Re: #quickscript-competition week two

[Stephen De Gabrielle]

Hi 

My apologies! 

You must signup to slack using the slack signup link 
https://racket-slack.herokuapp.com/
to access the *#quickscript-competition 
** channel. *(I should have 
realised that - and I should have posted this a week ago)

Its also fine to discuss on this list - maybe prefix the subject line with 
'#quickscript-competition ' so those who are not interested can skip past. 

Thanks 

Stephen

PS if you prefer chat another platform; mastodon, riot, discord, twitter or 
something else that is fine too - my handle is spdegabrielle on most 
things. Just remember the most active chat for racketeers is the racket 
slack.

On Thursday, July 9, 2020 at 3:37:34 PM UTC+1 Stephen De Gabrielle wrote:

> *#quickscript-competition ** 
> week 
> two*
>
> *Prizes: *In addition to the glory and admiration of your peers…
> If you participate once, you get stickers,
> if you participate twice time, you get also a mug,
> if you participate three times, you get also a t-shirt
> (while stocks last)
> *You can participate more than once per week. *
>
> *Thank you to the participants in week 1:*
>
>- Breakout 
> by 
> Jens 
>Axel Søgaard : The classic Breakout game in a single script!
>- Format-selection 
> by 
> Alex 
>Harsányi : Format comments to the Racket Style Guide standard.
>- Robo-Head-Pat 
>
> by Lambduli 
>
> 
>  : 
>It is like a good work sticker on your homework - but for code.
>- Rot13 Decode/Encode 
> by 
> Karrq 
>: Fraq naq qrpbqr frperg zrffntrf yvxr Wnzrf Obaq!
>
> *Don’t forget to check them out!*
>
> *PSA: You don’t need to install Quickscript - it is bundled in DrRacket!*
>
> *Week 2…*starts with a bang with two awesome entries by Laurent Orseau:
>
>- Letterfall: See you code fall like rocks! 
>
>- Run this quickscript to install all scripts from the competition! 
>
>
> *Looking for ideas?*
>
>- make a Code-Prettify script that uses pretty-print 
>
> 
> and *reindent* to prettify code.
>
> More at 
> https://github.com/Quickscript-Competiton/July2020entries/blob/master/IDEAS.md
>
> Enjoy!
> Stephen
>
>

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Re: [racket-users] Are Regular Expression classes Unicode aware?

[Peter W A Wood]

Dear Ryan

Thank you very much for the kind, detailed explanation which I will study 
carefully. It was not my intention to reply to you off-list. I hope I have 
correctly addressed this reply to appear on-list.

Peter

> On 10 Jul 2020, at 15:47, Ryan Culpepper  wrote:
> 
> (I see this went off the mailing list. If you reply, please consider CCing 
> the list.)
> 
> Yes, I understood your goal of trying to capture the notion of Unicode 
> "alphabetic" characters with a regular expression.
> 
> As far as I know, Unicode doesn't have a notion of "alphabetic", but it does 
> assign every code point to a "General category", consisting of a main 
> category and a subcategory. There is a category called "Letter", which seems 
> like one reasonable generalization of "alphabetic".
> 
> In Racket, you can get the code for a character's category using 
> `char-general-category`. For example:
> 
>   > (char-general-category #\A)
>   'lu
>   > (char-general-category #\é)
>   'll
>   > (char-general-category #\ß)
>   'll
>   > (char-general-category #\7)
>   'nd
> 
> The general category for "A" is "Letter, uppercase", which has the code "Lu", 
> which Racket turns into the symbol 'lu. The general category of "é" is 
> "Letter, lowercase", code "Ll", which becomes 'll. The general category of 
> "7" is "Number, decimal digit", code "Nd".
> 
> In Racket regular expressions, the \p{category} syntax lets you recognize 
> characters from a specific category. For example, \p{Lu} recognizes 
> characters with the category "Letter, uppercase", and \p{L} recognizes 
> characters with the category "Letter", which is the union of "Letter, 
> uppercase", "Letter, lowercase", and so on.
> 
> So the regular expression #px"^\\p{L}+$" recognizes sequences of one or more 
> Unicode letters. For example:
> 
>   > (regexp-match? #px"^\\p{L}+$" "héllo")
>   #t
>   > (regexp-match? #px"^\\p{L}+$" "straße")
>   #t
>   > (regexp-match? #px"^\\p{L}+$" "二の句")
>   #t
>   > (regexp-match? #px"^\\p{L}+$" "abc123")
>   #f ;; No, contains numbers
> 
> There are still some problems to watch out for, though. For example, accented 
> characters like "é" can be expressed as a single pre-composed code point or 
> "decomposed" into a base letter and a combining mark. You can get the 
> decomposed form by converting the string to "decomposed normal form" (NFD), 
> and the regexp above won't match that string.
> 
>   > (map char-general-category (string->list (string-normalize-nfd "é")))
>   '(ll mn)
>   > (regexp-match? #px"^\\p{L}+$" (string-normalize-nfd "héllo"))
>   #f
> 
> One fix would be to call `string-normalize-nfc` first, but some 
> letter-modifier pairs don't have pre-composed versions. Another fix would be 
> to expand the regexp to include modifiers. You'd have to decide which is 
> better based on your application.
> 
> Ryan
> 
> 
> 
> On Fri, Jul 10, 2020 at 2:10 AM Peter W A Wood  wrote:
> Ryan
> 
> > On 9 Jul 2020, at 22:52, Ryan Culpepper  wrote:
> > 
> > If you want a regular expression that does match the example string, you 
> > can use the \p{property} notation. For example:
> > 
> >   > (regexp-match? #px"^\\p{L}+$" "h\uFFC3\uFFA9llo")
> >   #t
> > 
> > The "Regexp Syntax" docs have a grammar for regular expressions with links 
> > to examples.
> > 
> > Ryan
> 
> Thanks. I used héllo as an example. I was wondering if there was a way of 
> specifying a regular expression group for Unicode “alphabetic” characters. 
> 
> On reflection, it seems a somewhat esoteric requirement that is almost 
> impossible to satisfy. By way of example, would 
> “Straße" be considered alphabetic? Would “二の句” be considered alphabetic?
> 
> Strangely, Python considered the Japanese characters as being alphabetic but 
> will not accept “Straße” as a valid string. (I suspect this is due to some 
> problem relating to Locale..
> 
>  >>> "二の句".isalpha()
> True
> >>> “Straße".isalpha()
>   File "", line 1
> “Straße".isalpha()
>   ^
> SyntaxError: invalid character in identifier
> 
> Clearly, trying to identify “Unicode” alphabetic characters is far from 
> straightforward, though it may well be useful in processing some language 
> texts.
> 
> Peter
> 
> 

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