On 2019-08-03 04:44, Zoltán Herczeg wrote:
I was faced with a need of nonfixed length lookbehind two times:
> 1. when data came by stream of 24kB blocks and I need to find a last
>numeric in each of it
> /.{24000}(?<=(\d++)\D*+)/g
Even if this would work, the result of this would be always the last
position of the subject, and that is probably not what you want.
May be I wrote not exactly accurate regex. May be it need (*SKIP). But it
is enough for understanding a goal. Result would be in capture group 1.
/(?s).*(?<!\d)\K(?=(\d++))/
This provides the starting position of the decimal number, with going
back from the input. This is also much faster than scanning [\G,n-1].
This can't help. I have a STREAM of data. Each subject can have any
length. For example 10 MB. And it consists of many 24kB blocks.
> 2. There are cases where there is no no programming language available
for
> user, only regex. And exactly this case is in one of my application.
If you have such issues frequently I would recommend to support some
scripting language. There are many small and fairly quick JS engines,
which are easy to add. If I remember correctly Duktape or <
Thanks, Zoltan. In my application I use Lua, I use many-many callouts. But
users are no programmers and no have access to Lua. They use ONLY regexes.
And using script language is very unperformance thing in critical code
sections.
I think we don't discuss how the tasks can be solved by programming
languages, but about what regexes can do. I think EVERY regex task I can
solve by write a number of programming language code. Isn't it?
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