[Philadelphia-pm] selective splitting?

[James E Keenan]

On 11/17/2016 08:40 PM, Morgan Jones wrote:
> mjd’s talk Monday has me thinking about peer review and how helpful it can be.  So here goes.  I can certainly work around this but as a learning experience I’m wondering if someone has a straightforward answer. Can I split on only instances of a character that is not surrounded by in this case parentheses?
>
> I have a semicolon separated string that contains a date, a string, an ip address and a user agent string.  The catch is the user agent string contains a semicolon however it’s between parentheses.  So what I want is to split on semicolons that are not surrounded by parentheses.
>
> For example:
> $v = ‘20161116172606Z;accepted-terms-of-use via CAS;192.168.1.5;Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_1) AppleWebKit/602.2.14 (KHTML, like Gecko) Version/10.0.1 Safari/602.2.14’;
>
> It seems to me I should be able to split like this:
> my ($date, $ignore, $ip, $agent) = split /[^\(]+[^\;]*\;[^\)]*[^\)]+/, $v;
>
> From a little reading I may need to use look aheads which are new to me.  Here’s an attempt at that that is of course not working:
> my ($date, $ignore, $ip, $agent) =
> 	    	split /(?<!()
>                        \;
>                        (?!))/x, $v;
>
>
> Does anyone have a suggestion or see what I’m missing?
>

I often find that trying to write the One Regex to Rule Them All is a 
time-consuming experience that leads to unreadable code.  Sometimes 
partially processing a string with one regex and then completing the 
processing with a second is more readable, even if not, in principle, as 
fast.

How far does this get you?

my ($date, $ignore, $ip, $agent) = split /;/, $v, 4;

Thank you very much.
Jim Keenan