I am trying to add a feature that works with certain unicode groups from a string. I found this question that suggests the following solution, which does work on the unicodes inside of the stated range:
s = Regex.Replace(s, #"[^\u0000-\u007F]", string.Empty);
This works fine.
In my research, though, I came across the use of unicode blocks, which I find to be far more readable.
InBasic_Latin = U+0000–U+007F
More often, I saw recommendations pointing people to use the actual codes themselves (\u0000-\u007F) rather than these blocks (InBasic_Latin). I could see the benefit of explicitly declaring a range when you need some subset of that block or a specific unicode, but when you really just want that entire grouping using the block declaration it seems more friendly to readability and even programmability to use the block name instead.
So, generally, my question is why would \u0000–\u007F be considered a better syntax than InBasic_Latin?
It depends on your regex engine, but some (like .NET, Java, Perl) do support Unicode blocks:
if (Regex.IsMatch(subjectString, #"\p{IsBasicLatin}")) {
// Successful match
}
Others don't (like JavaScript, PCRE, Python, Ruby, R and most others), so you need to spell out those codepoints manually or use an extension like Steve Levithan's XRegExp library for JavaScript.
Related
Word seems to use a different apostrophe character than Visual Studio and it is causing problems with using Regex.
I am trying to edit some Word documents in C# using OpenXML. I am basically replacing [[COMPANY]] with a company name. This has worked pretty smoothly until I have reached my corner case of companies with names that end in s. I end up with issue s where sometimes it creates a s's.
Example:
Company Name: Simmons
Text in Doc: The [[COMPANY]]'s business is cars.
Result: The Simmons's business is cars.
This is improper English.
I should be able to just use a basic find and replace like I did for [[COMPANY]], but it is not working.
Regex apostropheReplace = new Regex("s\\'s");
docText = apostropheReplace.Replace(docText, "s\'");
This does not. It seems that Word is using an different character for and apostrophe(') than the standard one that is created when I use the key on my keyboard in Visual Studio. If I write a find and replace using my keyboard it will not work, but if I copy and paste the apostrophe from Word it does.
Regex apostrophyReplace = new Regex("s\\’s");
docText = apostrophyReplace.Replace(docText, "s\'");
Notice the different character in the Regex for the second one. I'm confused as to why this is, and also want to know if the is a proper way of doing this. I tried "'" but that does not work. I just want to know if using the copied character from Word is the proper way of doing this, and is there a way to do it so that both characters work so I don't have an issue with docs that may be created with a different program.
The reason this happens is because they are different characters.
Word actually changes some punctuation characters after you type them in order to give them the right inclination or to improve presentation.
I ran in the very same issue before and I used this as regular expression: [\u2018\u2019\u201A\u201b\u2032']
So essentially modify your code to:
Regex apostropheReplace = new Regex("s\\[\u2018\u2019\u201A\u201b\u2032']s");
docText = apostropheReplace.Replace(docText, "s\'")
I found these were the five most common type of single quotes and apostrophes used.
And in case you come across the same issue with double quotes, here is what you can use: [\u201C\u201D\u201E\u201F\u2033\u2036\"]
Answering the question:
Is there a way to do it so that both characters work?
If you want one Regex to be able to handle both scenarios, this is perhaps a simple and readable solution:
Regex apostropheReplace = new Regex("s\\['’]s");
docText = apostropheReplace.Replace(docText, "s\'")
This has the added benefit of being understandable to other developers that you are attempting to cover both apostrophe cases. This benefit gets at the other part of your question:
If using the copied character from Word is the proper way of doing this?
That depends on what you mean by "proper". If you mean "most understandable to other developers," I'd say yes, because there would be the least amount of look-up needed to know exactly what your Regex is looking for. If you mean "most performant", that should not be an issue with this straightforward Regex search (some nice Regex performance tips can be found here).
If you mean "most versatile/robust single quote Regex", then as #Leonardo-Seccia points out, there are other character encodings that might cause trouble. (Some of the common Microsoft Word ones are listed here.) Such a solution might look like this:
Regex apostropheReplace =
new Regex("s\\['\u2018\u2019\u201A\u201b]s");
docText = apostropheReplace.Replace(docText, "s\'")
But you can certainly add other character encodings as needed. A more complete list of character encodings can be found here - to add them to the above Regex, simply change the "U+" to "u" and add it to the list after another "\" character. For example, to add the "prime" symbol (′ or U+2032) to the list above, change the RegEx string from
Regex("s\\['\u2018\u2019\u201A\u201b]s")
to
Regex("s\\['\u2018\u2019\u201A\u201b\u2032]s")
Ultimately, you would be the judge of what character encodings are the most "proper" for inclusion in your Regex based on your use cases.
I am making a programming language in native C++, with which I am making a basic editor in C#. NET WinForms. However, I am using a SyntaxRTB, with which I would like the Regex to catch the following error:
if declare is not succeeded by string / int / float / bool / array / char
How would I do that?
(The syntax to declare a variable is declare variable_type variable_name) - A whitespace would have to be accounted for too)
I have declare(?!string), but am still confused.
If you want a regex, you need a zero-width negative lookahead
But if you're constructing a language, this isn't the way to go. Full-blown language parsers are a different entity.
Although I agree with #fejesjoco, this is the expression I used here:
(declare)[\s](int|string|float|bool|array|char)[\s](.*)
Check for !match(pattern) to further diagnose an issue.
You are going to want to use Lookahead assertion. To be honest, I'm decent in Regex but I'm not really the guy you want explaining it to you.
This link will explain it better than I can, and this link provides a fairly decent Regex editor.
Hi I'm trying to figure out a way to remove the tags from the results returned from the Google Feed API. Specifically they are placing bold tags on titles and inside the description.
The codes that are being inserted are as follows:
\u003cb
\u003e
\u003c/b\u003e
Since its a fixed amount I did try doing a String.Replace() for each of these codes per string but it resulted in bad performance not surprisingly. I'm not sure if RegEx would be better (or worse). Does anyone have an idea on how to remove these? Google does not supply an option to remove tags from the results.
You could remove the unicode codes using a regex like this one:
\\u[\d\w]{4}
var subject = #"\u003cb\u003e\u003c/b\u003e";
var result = Regex.Replace(subject, #"\\u[\d\w]{4}", String.Empty);
As for performance, this article seems to suggest that regex is much slower, but i would run your own tests with your own data as it might be wildly different. The regular expression itself will play a big part in performance and I don't think that article states what the regex is being used so its impossible to compare. The size and type of your data will also play a big part, so it's difficult to say which is better without understanding your data.
Also, you should try compiling the regex with the RegexOptions.Compiled flag to see if that boosts performance.
I never use regular expression before and plan to use it to solve my problem but not quite sure whether it can help me.
I have a situation where I need store a rule or formula to build string values like following examples in a database field then retrieve this rule and build the string value.
FacilityCode + Left(ModelNO,2)
Right(PO,3) + Left(Serial,2)
Is this achievable using .net regular expression? Any good tutorial or simple examples of this problem.
Regexp : http://msdn.microsoft.com/en-us/library/2k3te2cs(VS.80).aspx
http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex.aspx
But it doesn't seems fitting :)
It might be better to code some random string generator. Regex is for searching data not creating data.
The thing to remember about regex is that it is like an aircraft carrier; it does one thing very very well, it does not do other jobs very well at all.
An aircraft carrier moves planes very well on the ocean; it does not make a cheese sandwich well AT ALL!!
That is to say, if you use regex when you shouldn't you will almost certainly use far more processing power than if you used another tool for that job. Html parsing comes to mind.
Regex is provided as part of System.Text.RegularExpressions, but you can't rely exclusively on it. It'll let you search existing strings, but you'll need to implement your own logic for building new strings based on what you find in the existing data.
Also, keep in mind that System.Text.RegularExpressions works differently from regexp in Perl and other implementations. For example, it doesn't recognize POSIX character class definitions.
Since you're new to regex, you might want to check out the "Regular Expressions User Guide" on zytrax.com. It's not as comprehensive as an O'Reilly manual, but it'll do as a start.
I need to implement something similar to wikilinks on my site. The user is entering plain text and will enter [[asdf]] wherever there is an internal link. Only the first five examples are really applicable in the implementation I need.
Would you use regex, what expression would do this? Is there a library out there somewhere that already does this in C#?
On the pure regexp side, the expression would rather be:
\[\[([^\]\|\r\n]+?)\|([^\]\|\r\n]+?)\]\]([^\] ]\S*)
\[\[([^\]\|\r\n]+?)\]\]([^\] ]\S*)
By replacing the (.+?) suggested by David with ([^\]\|\r\n]+?), you ensure to only capture legitimate wiki links texts, without closing square brackets or newline characters.
([^\] ]\S+) at the end ensures the wiki link expression is not followed by a closing square bracket either.
I am note sure if there is C# libraries already implementing this kind of detection.
However, to make that kind of detection really full-proof with regexp, you should use the pushdown automaton present in the C# regexp engine, as illustrated here.
I don't know if there are existing libraries to do this, but if it were me I'd probably just use regexes:
match \[\[(.+?)\|(.+?)\]\](\S+) and replace with \1\3
match \[\[(.+?)\]\](\S+) and replace with \1\2
Or something like that, anyway.
Although this is an old question and already answered, I thought I'd add this as an addendum for anyone else coming along. The existing two answers do all the real work and got me 90% there, but here is the last bit for anyone looking for code to get straight on with trying:
string html = "Some text with a wiki style [[page2.html|link]]";
html = Regex.Replace(html, #"\[\[([^\]\|\r\n]+?)\|([^\]\|\r\n]+?)\]\]([^\] ]\S*)", #"$2$3");
html = Regex.Replace(html, #"\[\[([^\]\|\r\n]+?)\]\]([^\] ]\S*)", #"$1$2");
The only change to the actual regex is I think the original answer had the replacement parts the wrong way around, so the href was set to the display text and the link was shown on the page. I've therefore swapped them.