Are regular expressions worth the hassle?

Question

It strikes me that regular expressions are not understood well by the majority of developers. It also strikes me that for a lot of problems where regular expressions are use

Answer 1

I see regex as a fast, readable and preferable way to perform pattern matching on string data. So many languages support regex for this reason. If you wanted to write string manipulation code to match say, a Canadian zip code, be my guest, but the regex equivalent is so much more succinct. Definitely worth it.

Answer 2

True, learning to decipher regexes is difficult -- but so is learning to decipher the hosting program code in the first place. But is that so difficult, that we would rather write out manual instruction for a person to perform? No -- because that would be ridiculously longer and complicated. Same thing for not using a properly-formed regex.

Answer 3

One thing that doesn't seem mentioned (from a quick scan of the answers above) is that regular expressions are useful outside of code too. That means they are worth the hassle for a coder, or even for end users.

For example, I just wrote a bunch of unit tests for a formatter. I then made a copy of the test, and used a single regex in my editor to invert values and resulting strings (changing the method name too), giving expected value to a string to parse...

Another example: in our product, we allow using regular expressions for searching or filtering columns of data: sometime it is useful to get only names starting with something, ending with something, with letters followed by digits, or similar: no need to be a master of regexes to use them.

In these cases, writing code isn't an option (well, I could have made a small Lua script in the first case, but it would have been longer) and performance isn't a major issue.

But even in code, I often find easier and more readable to use a simple regular expression than a bunch of substring() with complex offsets and whatnot. Beside, they shine to validate user input where, again, performance isn't an issue.

Answer 4

VB.net is best, No, C# is, No F# is the best. It's really more a matter of what will be the people maintaining be better suited to handle, in my opinion. That's more a flame question, than something that is absolutely answerable.

Personally I'd choose regex whenever there's complex string validation (phone numbers,emails, ss#, ip addresses) where there are well known regex's out there. Get it from regex.org, give attribution with a comment and/or get the authors permission whichever is appropriate, and be done with it.

Also, for extracting pieces of a string, or complex splitting of strings, regex can be a great time saver.

But if you're writing your own, rather than using someone else's, using something like regex buddy or sells brothers regexdesigner is a must for testing and validation.

Answer 5

I've found with reg ex it's easier to maintain, but fine tuning someone else's reg ex is a bit of a pain. I think you underestimate the developers by saying most people don't understand it. Usually what I found is that over time, requirements adjust, and the regex that used to validate something is no longer effective and attempting to remove portions that are no longer valid is harder than to just rewrite the entire thing.

Also, imagine if you were validating phone numbers, and you decided to use code instead of reg ex. So it amounts to let's say 20 lines. Over time, your company decides to expand to other regions where now the phone validation is no longer totally true. So you have to adjust it to fit the other requirements. It could be possible that the code would be harder to maintain because you have to adjust over 20 lines of code rather than simply removing the old reg ex, and replacing it with a new one.

However, I think code can be used in certain cases along with regex. For example, let's say you want to validate US phone numbers, in every case, it has 10 digits numbers, but there are literally a ton of ways to write it out. For example (xxx) xxx-xxxx, or xxx-xxx-xxxx, or xxx xxx xxxx, etc, etc, etc. So if you write reg ex, you'd have to account for each of the cases. However, if you just strip all non-numerics and spaces with a regex replace, then go for a second pass and check if it has 10 digits, you'd find it easier than accounting each and every possible way to write a phone number.

Answer 6

I would never wish for fewer options in programming. Regular expressions can be very powerful, but do require skill. I like problems that can be solved in a few lines of code. It is really cool how many elements of validation can be accomplished. As long as the code is commented on what the expression checks for, I do not see a problem. I also have never seen a professional programmer not know what a regex was. It is another tool in the tool box.