Re^11: regex to return line with name but not if it has a number

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Re^12: regex to return line with name but not if it has a number by Marshall (Canon) on Apr 03, 2017 at 23:10 UTC
You are quite correct in that 2nd, 3rd, etc is theoretically a possibility. I think a rather rare one, but nevertheless a possibility. If something like that shows up, then I would go with my second code snippet. And modify the tests on the proposed name to be something other than just doesn't contain a digit. Perhaps something as simple as just paying attention to digits at the start of the proposed name field (looks like that fits OP's data) `if (($name) = $line =~ /^\s-\s+(.+?)\s\\|/) { print "$name\n" unless $name =~ /^\d/; }` [download] I suppose that these two regex'es could be combined. But, most of the time (in my personal experience), reducing the number of regex expressions doesn't matter. Also sometimes a more complex regex runs more slowly than 2 more straight-forward ones. I can think of other weird looking stuff that could possibly cause this simple scheme to fail. When writing an ad-hoc report parser, I usually try to keep things as simple as possible and then run it against as much data as practical while I am developing it. If and when some weirdo case like "3rd" shows up, I add code to handle it. There is always some sort of trade-off between "perfection" and development time. For some modules and subs, I scour the universe looking for all possible cases and test against them. Other times, I go with something imperfect, but likely "good enough", especially when dealing with a format that is likely to change often and require re-coding anyway. There is a lot of YMMV in this stuff! I have one parser with a documented defect which can theoretically happen according to the report spec(s). However after a decade and millions of actual examples, it hasn't happened yet. So I haven't bothered to write code to handle this very rare and complicated to handle situation.	[reply] [d/l]

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Re^12: regex to return line with name but not if it has a number
by Marshall (Canon) on Apr 03, 2017 at 23:10 UTC

If something like that shows up, then I would go with my second code snippet. And modify the tests on the proposed name to be something other than just doesn't contain a digit. Perhaps something as simple as just paying attention to digits at the start of the proposed name field (looks like that fits OP's data)

if (($name) = $line =~ /^\s*-\s+(.+?)\s*\|/)
{   
   print "$name\n" unless $name =~ /^\d/; 
}
[download]

I can think of other weird looking stuff that could possibly cause this simple scheme to fail.

When writing an ad-hoc report parser, I usually try to keep things as simple as possible and then run it against as much data as practical while I am developing it. If and when some weirdo case like "3rd" shows up, I add code to handle it.

There is always some sort of trade-off between "perfection" and development time. For some modules and subs, I scour the universe looking for all possible cases and test against them. Other times, I go with something imperfect, but likely "good enough", especially when dealing with a format that is likely to change often and require re-coding anyway. There is a lot of YMMV in this stuff! I have one parser with a documented defect which can theoretically happen according to the report spec(s). However after a decade and millions of actual examples, it hasn't happened yet. So I haven't bothered to write code to handle this very rare and complicated to handle situation.

[reply]
[d/l]