We Keep Coding

How to match any repeated chunks of characters?

I've seen many questions similar to this but none quite like it.
I have strings like this:
HF-01-HF-01-01
FBC-FBC-04
OZYA-03A-OZYA-03A-03
QC-QC-02
and want them to be returned like so:
HF-01-01
FBC-04
OZYA-03A-03
QC-02
I can't figure this out and the other questions I've seen don't apply because 1) the repeated chunk is more than one character, 2) There are no spaces between the repetition.
Or is regex not the best way to do this?
EDIT:
Rules
Alpha chunks are never repeated more than one time.
Some chunks can be alphanumeric but also never repeated more than one
time.
The part that can be repeated would be from the start of the string
and any additional chunks by hyphen.
So you would never have something like HF-HF-01-01. But in this case using the above rules, it would become HF-01-01 since HF is the only part repeated from the beginning of the string.
Perhaps something like this would work:
Scan string to first hyphen, see if that matches anywhere else after first hyphen, if so scan to second hyphen, see if that matches anywhere else, if not, take the first scan and remove one instance of it from the string, if so, scan to third, etc.
But I don't know how to do that in regex.

I'm not sure if RegExp is the right tool here.
Using MoreLinq RunLengthEncode method (that implement R.L.E.) you can achieve it like this:
string RemoveDuplicate(string input)
{
var chunks = input.Split('-') // cut at -
.RunLengthEncode() // group and count adjacent equals chunck
.Select(kvp => kvp.Key);// just take the chunk value
return string.Join("-", chunks); // reglue with -
}
Edit
Doesn't work for:
OZYA-03A-OZYA-03A-03

I guess,
([^-\r\n]+-|[^-\r\n]+-[^-\r\n]+-)(\1.*)
or with start/end anchors,
^([^-\r\n]+-|[^-\r\n]+-[^-\r\n]+-)(\1.*)$
might work to some extent and the desired output is in the last capturing group:
(\1.*)
RegEx Demo 1
RegEx Demo 2
Test
using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = #"([^-\r\n]+-|[^-\r\n]+-[^-\r\n]+-)(\1.*)";
string input = #"HF-01-HF-01-01
FBC-FBC-04
OZYA-03A-OZYA-03A-03
QC-QC-02
and want them to be returned like so:
HF-01-01
FBC-04
OZYA-03A-03
QC-02";
RegexOptions options = RegexOptions.Multiline;
foreach (Match m in Regex.Matches(input, pattern, options))
{
Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index);
}
}
}
If you wish to simplify/modify/explore the expression, it's been explained on the top right panel of regex101.com. If you'd like, you can also watch in this link, how it would match against some sample inputs.
RegEx Circuit
jex.im visualizes regular expressions:

I'm not sure if regex is the right tool here, but atleast it can be somewhat done with this short pattern:
^([A-Z0-9]+)-.*(\1.*)$
Explanation:
^ start of string
( group 1 start
[A-Z0-9]+ one or more capital letters or digits
) end group 1
- literal
.* any number of any chars
( group 2 start
\1 anything that was matched in group 1
.* any number of any chars
) end group 2 (this group will be used as the result)
$ end of string

C# Regex to obtain string up until a pattern

I've always been really bad when it comes to using regular expressions but it is something I want to seriously understand because as we all know, it is quite useful.
This is for a personal project, to keep my folders organized and neat.
I have a bunch of folders with the following naming pattern XXXXXXXX.XXXXXXX.XXXXXX.SYY.EYY.SOMETHINGELSE
There can be any amount of X repeating separated by ".", but the SYY.EYY is always there. So what I want is a regular expression to retrieve all the text represented by XXX without the "." if possible up until the SYY.EYY pattern.
I managed to detect the pattern because YY are always numbers, so doing something like \d{2} will detect it but I'm wondering if its possible to also add the rest of the pattern to that \d{2}.
Any help is appreciate it :)

If the YY is as you stated 2 digits and you want to get the text except the . up until for example S11.E22 you could make use of the \G anchor and a capturing group to get the text without a dot.
The value is in the Match.Groups property.
\G(?!S[0-9]{2}\.E[0-9]{2})([^.]+)\.
In parts
\G Assert position at the end of previous match (start at the beginning)
(?! Negative lookahead, assert what is directly to the right is not
S[0-9]{2}\.E[0-9]{2} Math S, 2 digits, . E and 2 digits
) Close lookahead
( Capture group 1
[^.]+ Match 1+ times any char except a dot
) Close group 1
\. Match dot literal
Regex demo | C# demo
For example
string pattern = #"\G(?!S[0-9]{2}\.E[0-9]{2})([^.]+)\.";
string input = #"XXXXXXXX.XXXXXXX.XXXXXX.S11.E22.SOMETHINGELSE";
foreach (Match m in Regex.Matches(input, pattern))
{
Console.WriteLine(m.Groups[1].Value);
}
Output
XXXXXXXX
XXXXXXX
XXXXXX

You can "replace/cut" the "." with C#.
The regex to get up until the SYY.EYY can be like this:
.SYY.EYY$
Line ends with word -> Regex: ExampleWord$

I would do something like:
var leftPart = Regex.Match(x, "^.*?(?=SYY)").Captures.First().Value;
// this now has XXXXXXXX.XXXXXXX.XXXXXX.
// And we can:
var left = leftPart.Replace(".", " "); // or any other char

Regex - The minus sign is not getting caught when processing float numbers in C#

I'm trying to extract 2 numbers from the following string (named interim):
"location" : { "lat" : 42.3875968, "lng" : -71.0994968 },
Here's the code I use in C#:
// define a regex for float numbers
Regex rx = new Regex(#"\b-?[0-9]*\.?[0-9]+\b", RegexOptions.Compiled | RegexOptions.IgnoreCase);
// Find matches.
MatchCollection matches = rx.Matches(interim);
return matches[0].ToString() + ", " + matches[1].ToString();
The return is "42.3875968, 71.0994968", without the minus sign for the second float number.
I debugged into the code that can confirm that the "-" is not in the result of matches var.
I've also tested the following regexes, for the same result:
[-+]?[0-9]*\.?[0-9]+
(-|+)?[0-9]*\.?[0-9]+
(-|\+)?[0-9]*\.?[0-9]+
(-\+)?[0-9]*\.?[0-9]+
Any one have an idea why this doesn't work?
Thanks,
Mylo

I suspect that your problem is that the \b at the beginning and end of your expression are not what you really want. It will work if you remove them and just use #"-?[0-9]*\.?[0-9]+".
What those do is ensure there is a boundary between word and non-word characters. This is almost certainly not what you want.

Your regular expression is wrong in the code above for the string you're reading.
If you use a regex tester for c# you'll see that the above regex "\b-?[0-9]*\.?[0-9]+\b" does not include the minus sign. If you change it slightly to "\b*-?[0-9]*\.?[0-9]+\b" then you will capture the - sign in the match.
Source: http://regexhero.net/tester/

Others say the \b is causing problems.
It could be all you need is something like this:
// ([-+]?[0-9]*\.?[0-9]*(?<=\d\.|\d))
( # (1 start)
[-+]? [0-9]* \.? [0-9]*
(?<= \d \. | \d )
) # (1 end)
Edit:
Comments are broken for my login.
To #JNYRanger
\b*-?[0-9]*\.?[0-9]+\b
\b* means optionally match a word boundry forever.
\b? means optionally match a word boundry once.
\b means match a word boundry once.
\b is a zero-width assertion, if its optional, usually don't include it.

regex for capturing digits and digit ranges

i have the following string
Fat mass loss was 2121,323.222 greater for GPLC (2–2.4kg vs. 0.5kg)
i want to capture
212,323.222
2-2.24
0.5
i.e. i want the above three results from the string,
can any one help me with this regex

I noticed that your hyphen in 2–2.4kg is not really hyphen, its a unicode 0x2013 "DASH".
So, here is another regex in C#
#"[0-9]+([,.\u2013-][0-9]+)*"
Test
MatchCollection matches = Regex.Matches("Fat mass loss was 2121,323.222 greater for GPLC (2–2.4kg vs. 0.5kg)", #"[0-9]+([,.\u2013-][0-9]+)*");
foreach (Match m in matches) {
Console.WriteLine(m.Groups[0]);
}
Here is the results, my console does not support printing unicode char 2013, so its "?" but its properly matched.
2121,323.222
2?2.4
0.5

Okay I didn't notice the C# tag until now. I will leave the answer but I know that's not what you expected, see if you can do something with it. Perhaps the title should have mentioned the programming language?
Sure:
Fat mass loss was (.*) greater for GPLC \((.*) vs. (.*)kg\)
Find your substrings in \1, \2 and \3.
If for Emacs, swap all parentheses and escaped parentheses.

How about something like this:
^.*((?:\d+,)*\d+(?:\.\d+)?).*(\d+(?:\.\d+)?(?:-\d+(?:\.\d+))?).*(\d+(?:\.\d+)).*$
A little more general, I think. I'm a little concerned about .* being greedy.

Fat mass loss was 2121,323.222 greater
for GPLC (2–2.4kg vs. 0.5kg)
a generalized extractor:
/\D+?([\d\,\.\-]+)/g
explanation:
/ # start pattern
\D+ # 1 or more non-digits
( # capture group 1
[\d,.-]+ # character class, 1 or more of digits, comma, period, hyphen
) # end capture group 1
/g # trailing regex g modifier (make regex continue after last match)
sorry I don't know c# well enough for a full writeup, but the pattern should plug right in.
see: http://www.radsoftware.com.au/articles/regexsyntaxadvanced.aspx for some implementation examples.

I came out with something like this atrocity:
-?\d(?:,?\d)*(?:\.(?:\d(?:,?\d)*\d|\d))?(?:[–-]-?\d(?:,?\d)*(?:\.(?:\d(?:,?\d)*\d|\d))?)?
Out of witch -?\d(?:,?\d)*(?:\.(?:\d(?:,?\d)*\d|\d))? is repeated twice, with – in the middle (note that this is a long hyphen).
This should take care of dots and commas outside of numbers, eg: hello,23,45.2-7world - will capture 23,45.2-7.

It looks like you're trying to find all numbers in the string (possibly with commas inside the number), and all ranges of numbers such as "2-2.4". Here is a regex that should work:
\d+(?:[,.-]\d+)*
From C# 3, you can use it like this:
var input = "Fat mass loss was 2121,323.222 greater for GPLC (2-2.4kg vs. 0.5kg)";
var pattern = #"\d+(?:[,.-]\d+)*";
var matches = Regex.Matches(input, pattern);
foreach ( var match in matches )
Console.WriteLine(match.Value);

Hmm, this is a tricky question, especially because the input string contains unicode character – (EN DASH) instead of - (HYPHEN-MINUS). Therefore the correct regex to match the numbers in the original string would be:
\d+(?:[\u2013,.]\d+)*
If you want a more generic approach would be:
\d+(?:[\p{Pd}\p{Pc}\p{Po}]\d+)*
which matches dash punctuation, connecter punctuation and other punctuation. See here for more information about those.
An implementation in C# would look like this:
string input = "Fat mass loss was 2121,323.222 greater for GPLC (2–2.4kg vs. 0.5kg)";
try {
Regex rx = new Regex(#"\d+(?:[\p{Pd}\p{Pc}\p{Po}\p{C}]\d+)*", RegexOptions.IgnoreCase | RegexOptions.Multiline);
Match match = rx.Match(input);
while (match.Success) {
// matched text: match.Value
// match start: match.Index
// match length: match.Length
match = match.NextMatch();
}
} catch (ArgumentException ex) {
// Syntax error in the regular expression
}

Let's try this one :
(?=\d)([0-9,.-]+)(?<=\d)
It captures all expressions containing only :
"[0-9,.-]" characters,
must start with a digit "(?=\d)",
must finish with a digit "(?<=\d)"
It works with a single digit expression and does not include beginning or trailing [.,-].
Hope this helps.

I got the solution to my problem.
The following is the Regex that gave my desired result:
(([0-9]+)([–.,-]*))+

C# regex to replace a delimiter by another one

I'm working on pl/sql code where i want to replace ';' which is commented with '~'.
e.g.
If i have a code as:
--comment 1 with;
select id from t_id;
--comment 2 with ;
select name from t_id;
/*comment 3
with ;*/
Then i want my result text as:
--comment 1 with~
select id from t_id;
--comment 2 with ~
select name from t_id;
/*comment 3
with ~*/
Can it be done using regex in C#?

Regular expression:
((?:--|/\*)[^~]*)~(\*/)?
C# code to use it:
string code = "all that text of yours";
Regex regex = new Regex(#"((?:--|/\*)[^~]*)~(\*/)?", RegexOptions.Multiline);
result = regex.Replace(code, "$1;$2");
Not tested with C#, but the regular expression and the replacement works in RegexBuddy with your text =)
Note: I am not a very brilliant regular expression writer, so it could probably have been written better. But it works. And handles both your cases with one-liner-comments starting with -- and also the multiline ones with /* */
Edit: Read your comment to the other answer, so removed the ^ anchor, so that it takes care of comments not starting on a new line as well.
Edit 2: Figured it could be simplified a bit. Also found it works fine without the ending $ anchor as well.
Explanation:
// ((?:--|/\*)[^~]*)~(\*/)?
//
// Options: ^ and $ match at line breaks
//
// Match the regular expression below and capture its match into backreference number 1 «((?:--|/\*)[^~]*)»
// Match the regular expression below «(?:--|/\*)»
// Match either the regular expression below (attempting the next alternative only if this one fails) «--»
// Match the characters “--” literally «--»
// Or match regular expression number 2 below (the entire group fails if this one fails to match) «/\*»
// Match the character “/” literally «/»
// Match the character “*” literally «\*»
// Match any character that is NOT a “~” «[^~]*»
// Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «*»
// Match the character “~” literally «~»
// Match the regular expression below and capture its match into backreference number 2 «(\*/)?»
// Between zero and one times, as many times as possible, giving back as needed (greedy) «?»
// Match the character “*” literally «\*»
// Match the character “/” literally «/»

A regex is not really needed - you can iterate on lines, locate the lines starting with "--" and replace ";" with "~" on them.
String.StartsWith("--") - Determines whether the beginning of an instance of String matches a specified string.
String.Replace(";", "~") - Returns a new string in which all occurrences of a specified Unicode character or String in this instance are replaced with another specified Unicode character or String.