Re: [Bug-apl] Regex support

[enztec]

<mumble> anyone who loves grep and hates perl (and i hope java too) can't be 
all bad </mumble>

using apl like syntax is good    aaa' ⎕REX['s'] 'bbb'      what would monadic   
⎕REX['s'] 'bbb'      return?

On Wed, 20 Sep 2017 21:47:29 +0200
Juergen Sauermann <address@hidden> wrote:

> Hi Elias,
> 
> I am generally in favour of supporting regular expressions in GNU APL.
> 
> We should do that in a way that is compatible with the way in which the most 
> commonly used libraries
> do that (even if they are lacking some features that more exotic libraries 
> may have. Unfortunately I do not
> have a full overview of all (or even any) existing libraries. I personally 
> love grep and hate perl (the latter not
> only because of their regexes).
> 
> I would like to avoid constructs like s/aaa/bbb/ where operations are kind of 
> text-encoded into strings.
> That is, IMHO, a  hack-ish programming style and should be replaced by a more 
> APL-alike syntax such as
> 'aaa' ⎕REX['s'] 'bbb' or maybe 's' ⎕REX 'aaa' 'bbb'.
> 
> Or, if the number of operations is small (perl seems to have only 2, not 
> counting the translate which is already
> covered by other APL functions), then we could also have different 
> ⎕-functions for them and thus avoiding a
> third argument.
> 
> Everybody else, please feel invited to join the discussion.
> 
> Best Regards,
> Jürgen Sauermann
> 
> 
> On 09/20/2017 05:59 AM, Elias Mårtenson wrote:
> On several occasions, I have felt that built-in regex support in GNU APL 
> would be very helpful.
> 
> Implementing it should be rather simple, but I'd like to discuss how such an 
> API should look in order for it to be as useful as possible.
> 
> I was thinking of the following form:
> 
>       regex ⎕Regex string
> 
> The way I envision this to work, is to have the function return ⍬ if there is 
> no match, or a string containing the match, if there is one:
> 
>       'f..' ⎕Regex 'xzooy'
> ┏⊖┓
> ┃0┃
> ┗━┛
>       'f..' ⎕Regex 'xfooy'
> 'foo'
> 
> If the regex has subexpressions, those matches should be returned as 
> individual strings:
> 
>       '([0-9]+)-([0-9]+)-([0-9]+) '⎕Regex '2017-01-02'
> ┏→━━━━━━━━━━━━━━━┓
> ┃"2017" "01" "02"┃
> ┗∊━━━━━━━━━━━━━━━┛
> 
> This would be a very useful API, and reasonably easy to implement by simply 
> calling into the standard regcomp() call: 
> http://pubs.opengroup.org/onlinepubs/009695399/functions/regcomp.html
> 
> What do you think? Is this a reasonable way to implement it? Any suggestions 
> about alternative API's?
> 
> Regards,
> Elias
>