I think you have a point. It would be very useful to be able to have ⎕RE
filter the results for you.
In experimenting with your specific case, I came across another use-case
that might warrant another flag: One that does not return the full match,
but only the parenthesised subexpressions (this used to be the default in
my initial draft version). Now I have to use 1↓ to remove this.
Here is my somewhat realistic test case that takes the log file, and
extracts the date and the name of the service that was started or stopped:
* file ← ⎕FIO[49] "/some/file/name"*
* x ← "^([a-zA-Z]{3} [0-9]+ [0-9]{2}:[0-9]{2}:[0-9]{2}).*:
(Started|Stopped) (.*)$" ⎕RE file*
* ⍴ x*
┏→━━━━┓
┃69339┃
┗━━━━━┛
* result ← ⊃ 1↓¨ ({⍬≢⍵}¨x) / x*
* ⍴ result*
┏→━━━━━┓
┃7269 3┃
┗━━━━━━┛
This is a lot more complicated than it needs to be. The two new flags
mentioned would completely remove the last line and replace it with a
simple pair of ⎕RE["XY"] flags.
Regards,
Elias
On 11 October 2017 at 11:12, Christian Robert <christian.rob...@polymtl.ca>
wrote:
> Sometimes we only want to know if it match or not.
>
> I suggest a new flag ['m'] (as match) that will return ...
>
> for a string: either 0 or 1 as a scalar for "not matching" or "matching"
> for an array of strings: a vector of 0/1 for each string saying like
> above.
>
>
> lets say:
>
> z←⎕fio[49] '/var/log/messages' // beware that this file is
> inaccessible by default unless being "root" on linux
> // or you chmod a+r
> /var/log/messages # as root
>
> who may return 50,000 lines or even 2 millions, on an average of say ~120
> characters each.
>
>
> I would hope to be able to use a flag as ['m']:
>
> 'Started|Stopped' ⎕RE['m'] z
>
> who will return an array of (0/1) telling which lines match or not the
> pattern, so I can
> only retain those matching for further fine tuning (via diadic operator
> "/").
>
> It will be a LOT faster than letting ⎕RE returning the whole result of
> pcre2 INTO the physical Gnu-APL memory engine
> creating a lot of integers arrays for no real purpose, ie: seen from the
> application.
>
> comments welcome,
>
> my usual 2 cents,
> Xtian.
>
>
