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Understanding Regular Expressions 2: Groups and Captures

27 points by liquidise 12y ago

junto 12y ago
Python and .NET also have named groups/captures. I find that particularly useful when dealing with more complex expressions. http://www.regular-expressions.info/named.html http://www.regular-expressions.info/named.html
- liquidise 12y ago
  Very true. I plan on writing about those in a coming post, along with zero-widths and look aheads/behinds. It has been a challenge trying to distill such a powerful tool into its logical building blocks, without biting off too much in any individual post.
zo1 12y ago
Comment on a tangent. I often find people absolutely baffled, and at the same time amazed at regular expressions. I am, of course, referring to my coworkers, whom I try to convince to at least attempt at using regular expressions. Unfortunately, no matter how many cheat-sheets I print and handout, or how many times I wow them with simple yet powerful regular expressions, they resort to using the proverbial brute-force hammer that they know. Has anyone had any positive luck with convincing/converting coworkers into using more regular expressions?
- jefe78 12y ago
  The most luck I had with this was tackling a massive problem with something elegant then offering the idea of regular expressions when a similar problem came up for my colleagues.
- deleted 12y ago
  [deleted]
- acjohnson55 12y ago
  Regex as a language kind of sucks. If you don't use it on a daily basis, it's pretty easy to let your understandability of it slip to the point where the average regex looks like symbol soup. At the cost of terseness, I think representing regexes as a chain of operations would be much more practical. I've seen at least one library do this on HN probably a couple years back, and it was roundly derided in the comments. But failing adoption of such a library, there's not a whole lot of excuse for a professional programmer not to be able to look up some syntax to whip up a regex in cases where it's the right tool for the job.
- leeoniya 12y ago
  just show them the equivalent amount of code that includes the lexer/parser and validation logic that can be summarized by even a simple regex. aversion to regex is like aversion to SQL. sometimes declarative saves literally hundreds of lines of hard-to-understand, poorly optimized code.
  - liquidise 12y ago
    i used to try this, but young programmers especially tend to just leave thinking "regex is so powerful but i don't know it", which was likely their mindset going in anyway.
- rndmize 12y ago
  I acquired a dislike of regexes in school, and it wasn't until I found http://www.regexr.com http://www.regexr.com that I felt I could efficiently figure out how to use them (and started to feel that they were seriously awesome). I think that regexes, like so many programming tools/utilities, have such a frustrating initial learning period that many people don't want to bother. Regexr sidesteps this by not only having hints/cheat sheets on the side, but it shows you your results as you construct it; faster feedback = faster learning.
- wodenokoto 12y ago
  If people don't want to learn it, it won't happen. With that being said, I found the introduction to regular expressions in Speech and Language Processing, by Daniel Jurafsky to be the only one where it clicked for me what was going on.
georgiecasey 12y ago
RegexBuddy is the best €30 I spent for speeding up and testing expressions. Pity it doesn't support OBjC though.

27 points by liquidise 12y ago

junto 12y ago

Python and .NET also have named groups/captures. I find that particularly useful when dealing with more complex expressions. http://www.regular-expressions.info/named.html http://www.regular-expressions.info/named.html

liquidise 12y ago
Very true. I plan on writing about those in a coming post, along with zero-widths and look aheads/behinds. It has been a challenge trying to distill such a powerful tool into its logical building blocks, without biting off too much in any individual post.

zo1 12y ago

Comment on a tangent. I often find people absolutely baffled, and at the same time amazed at regular expressions. I am, of course, referring to my coworkers, whom I try to convince to at least attempt at using regular expressions. Unfortunately, no matter how many cheat-sheets I print and handout, or how many times I wow them with simple yet powerful regular expressions, they resort to using the proverbial brute-force hammer that they know. Has anyone had any positive luck with convincing/converting coworkers into using more regular expressions?

jefe78 12y ago
The most luck I had with this was tackling a massive problem with something elegant then offering the idea of regular expressions when a similar problem came up for my colleagues.
deleted 12y ago
[deleted]
acjohnson55 12y ago
Regex as a language kind of sucks. If you don't use it on a daily basis, it's pretty easy to let your understandability of it slip to the point where the average regex looks like symbol soup. At the cost of terseness, I think representing regexes as a chain of operations would be much more practical. I've seen at least one library do this on HN probably a couple years back, and it was roundly derided in the comments. But failing adoption of such a library, there's not a whole lot of excuse for a professional programmer not to be able to look up some syntax to whip up a regex in cases where it's the right tool for the job.
leeoniya 12y ago
just show them the equivalent amount of code that includes the lexer/parser and validation logic that can be summarized by even a simple regex. aversion to regex is like aversion to SQL. sometimes declarative saves literally hundreds of lines of hard-to-understand, poorly optimized code.
- liquidise 12y ago
  i used to try this, but young programmers especially tend to just leave thinking "regex is so powerful but i don't know it", which was likely their mindset going in anyway.
rndmize 12y ago
I acquired a dislike of regexes in school, and it wasn't until I found http://www.regexr.com http://www.regexr.com that I felt I could efficiently figure out how to use them (and started to feel that they were seriously awesome). I think that regexes, like so many programming tools/utilities, have such a frustrating initial learning period that many people don't want to bother. Regexr sidesteps this by not only having hints/cheat sheets on the side, but it shows you your results as you construct it; faster feedback = faster learning.
wodenokoto 12y ago
If people don't want to learn it, it won't happen. With that being said, I found the introduction to regular expressions in Speech and Language Processing, by Daniel Jurafsky to be the only one where it clicked for me what was going on.

georgiecasey 12y ago

RegexBuddy is the best €30 I spent for speeding up and testing expressions. Pity it doesn't support OBjC though.