Mrthfx

Equivalent of "illegal" for violating civil law

Why do neural networks need so many training examples to perform?

What makes papers publishable in top-tier journals?

A Missing Symbol for This Logo

Is there a verb that means to inject with poison?

Count repetitions of an array

Non-Cancer terminal illness that can affect young (age 10-13) girls?

Why do we have to make "peinlich" start with a capital letter and also end with -s in this sentence?

What is the wife of a henpecked husband called?

How to deal with possible delayed baggage?

Does a paladin have to announce that they're using Divine Smite before attacking?

What species should be used for storage of human minds?

Which RAF squadrons and aircraft types took part in the bombing of Berlin on the 25th of August 1940?

How to delete duplicate text from a file?

Why do all the books in Game of Thrones library have their covers facing the back of the shelf?

What game did these black and yellow dice come from?

Am I correct in stating that the study of topology is purely theoretical?

How can I play a serial killer in a party of good PCs?

Is there any danger of my neighbor having my wife's signature?

Why is a temp table a more efficient solution to the Halloween Problem than an eager spool?

If angels and devils are the same species, why would their mortal offspring appear physically different?

Why did the villain in the first Men in Black movie care about Earth's Cockroaches?

How to access internet and run apt-get through a middle server?

When obtaining gender reassignment/plastic surgery overseas, is an emergency travel document required to return home?

Regex Replace seems to replace only first occurrence

Match all occurrences of a regexA comprehensive regex for phone number validationHow to replace all occurrences of a string in JavaScriptHow to RegEx Replace named groupsRegEx match open tags except XHTML self-contained tagsRegex: matching up to the first occurrence of a characterRegex replace matched and remove not matchedJavaScript RegEx - replace first and last occurrence of a characterRegex for replacing first 5 numbers, irrespective of anything between them?Replace all occurrences of a white space from string except the first occurrence using Regex in C#

6

I have a string, from which I want to remove the whitespaces between the numbers:

string test = "Some Words 1 2 3 4";

string result = Regex.Replace(test, @"(d)s(d)", @"$1$2");

the expected/desired result would be:

"Some Words 1234"

but I retrieve the following:

"Some Words 12 34"

What am I doing wrong here?

Further examples:

Input:  "Some Words That Should not be replaced 12 9 123 4 12"

Output: "Some Words That Should not be replaced 129123412"



Input:  "test 9 8"

Output: "test 98"



Input:  "t e s t 9 8"

Output: "t e s t 98"



Input:  "Another 12 000"

Output: "Another 12000"

c# regex

share|improve this question

edited 2 hours ago

DMA

557

asked 2 hours ago

nntynnty

665

add a comment | 

6

I have a string, from which I want to remove the whitespaces between the numbers:

string test = "Some Words 1 2 3 4";

string result = Regex.Replace(test, @"(d)s(d)", @"$1$2");

the expected/desired result would be:

"Some Words 1234"

but I retrieve the following:

"Some Words 12 34"

What am I doing wrong here?

Further examples:

Input:  "Some Words That Should not be replaced 12 9 123 4 12"

Output: "Some Words That Should not be replaced 129123412"



Input:  "test 9 8"

Output: "test 98"



Input:  "t e s t 9 8"

Output: "t e s t 98"



Input:  "Another 12 000"

Output: "Another 12000"

c# regex

share|improve this question

edited 2 hours ago

DMA

557

asked 2 hours ago

nntynnty

665

add a comment | 

I have a string, from which I want to remove the whitespaces between the numbers:

string test = "Some Words 1 2 3 4";

string result = Regex.Replace(test, @"(d)s(d)", @"$1$2");

the expected/desired result would be:

"Some Words 1234"

but I retrieve the following:

"Some Words 12 34"

What am I doing wrong here?

Further examples:

Input:  "Some Words That Should not be replaced 12 9 123 4 12"

Output: "Some Words That Should not be replaced 129123412"



Input:  "test 9 8"

Output: "test 98"



Input:  "t e s t 9 8"

Output: "t e s t 98"



Input:  "Another 12 000"

Output: "Another 12000"

c# regex

share|improve this question

edited 2 hours ago

DMA

557

asked 2 hours ago

nntynnty

665

string test = "Some Words 1 2 3 4";

string result = Regex.Replace(test, @"(d)s(d)", @"$1$2");

"Some Words 1234"

"Some Words 12 34"

Input:  "Some Words That Should not be replaced 12 9 123 4 12"

Output: "Some Words That Should not be replaced 129123412"



Input:  "test 9 8"

Output: "test 98"



Input:  "t e s t 9 8"

Output: "t e s t 98"



Input:  "Another 12 000"

Output: "Another 12000"

share|improve this question

edited 2 hours ago

DMA

557

asked 2 hours ago

nntynnty

665

share|improve this question

edited 2 hours ago

DMA

557

asked 2 hours ago

nntynnty

665

edited 2 hours ago

DMA

557

edited 2 hours ago

DMA

557

asked 2 hours ago

nntynnty

665

asked 2 hours ago

nntynnty

665

2 Answers
2

active

oldest

votes

8

Regex.Replace continues to search after the previous match:

Some Words 1 2 3 4

           ^^^

         first match, replace by "12"



Some Words 12 3 4

             ^

             +-- continue searching here



Some Words 12 3 4

              ^^^

            next match, replace by "34"

You can use a zero-width positive lookahead assertion to avoid that:

string result = Regex.Replace(test, @"(d)s(?=d)", @"$1");

Now the final digit is not part of the match:

Some Words 1 2 3 4

           ^^?

         first match, replace by "1"



Some Words 12 3 4

            ^

            +-- continue searching here



Some Words 12 3 4

            ^^?

            next match, replace by "2"



...

share|improve this answer

edited 2 hours ago

answered 2 hours ago

HeinziHeinzi

123k38271408

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Wanted to explain, but it wasn't easy. Yours were the best explanation 👍
  
  – DMA
  2 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you for the detailed explanation !
  
  – nnty
  2 hours ago
  

  
  
  
  

add a comment | 

9

Your regex consumes the digit on the right. (d)s(d) matches and captures 1 in Some Words 1 2 3 4 into Group 1, then matches 1 whitespace, and then matches and consumes (i.e. adds to the match value and advances the regex index) 2. Then, the regex engine tries to find another match from the current index, that is already after 1 2. So, the regex does not match 2 3, but finds 3 4.

Here is your regex demo and a diagram showing that:

Also, see the process of matching here:

Use lookarounds instead that are non-consuming:

(?<=d)s+(?=d)

See the regex demo

Details

• 
  (?<=d) - a positive lookbehind that matches a location in string immediately preceded with a digit


• 
  s+ - 1+ whitespaces


• 
  (?=d) - a positive lookahead that matches a location in string immediately followed with a digit.

C# demo:

string test = "Some Words 1 2 3 4";

string result = Regex.Replace(test, @"(?<=d)s+(?=d)", "");

See the online demo:

var strs = new List<string> {"Some Words 1 2 3 4", "Some Words That Should not be replaced 12 9 123 4 12", "test 9 8", "t e s t 9 8", "Another 12 000" };

foreach (var test in strs) 

{

    Console.WriteLine(Regex.Replace(test, @"(?<=d)s+(?=d)", ""));

}

Output:

Some Words 1234

Some Words That Should not be replaced 129123412

test 98

t e s t 98

Another 12000

share|improve this answer

edited 52 mins ago

answered 2 hours ago

Wiktor StribiżewWiktor Stribiżew

319k16139221

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you ! Good answer, but @heinzi 's explanation was a little bit more clearer. Therefore I accepted his answer.
  
  – nnty
  2 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @nnty Ok, just in case, I added diagrams.
  
  – Wiktor Stribiżew
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @nnty I hope the animation showing how your regex works is fine.
  
  – Wiktor Stribiżew
  52 mins ago
  

  
  
  
  

add a comment | 

Your Answer

StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f54883163%2fregex-replace-seems-to-replace-only-first-occurrence%23new-answer', 'question_page');
}
);

Post as a guest

Name

Email

Required, but never shown

8

Regex.Replace continues to search after the previous match:

Some Words 1 2 3 4

           ^^^

         first match, replace by "12"



Some Words 12 3 4

             ^

             +-- continue searching here



Some Words 12 3 4

              ^^^

            next match, replace by "34"

You can use a zero-width positive lookahead assertion to avoid that:

string result = Regex.Replace(test, @"(d)s(?=d)", @"$1");

Now the final digit is not part of the match:

Some Words 1 2 3 4

           ^^?

         first match, replace by "1"



Some Words 12 3 4

            ^

            +-- continue searching here



Some Words 12 3 4

            ^^?

            next match, replace by "2"



...

share|improve this answer

edited 2 hours ago

answered 2 hours ago

HeinziHeinzi

123k38271408

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Wanted to explain, but it wasn't easy. Yours were the best explanation 👍
  
  – DMA
  2 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you for the detailed explanation !
  
  – nnty
  2 hours ago
  

  
  
  
  

add a comment | 

8

Regex.Replace continues to search after the previous match:

Some Words 1 2 3 4

           ^^^

         first match, replace by "12"



Some Words 12 3 4

             ^

             +-- continue searching here



Some Words 12 3 4

              ^^^

            next match, replace by "34"

You can use a zero-width positive lookahead assertion to avoid that:

string result = Regex.Replace(test, @"(d)s(?=d)", @"$1");

Now the final digit is not part of the match:

Some Words 1 2 3 4

           ^^?

         first match, replace by "1"



Some Words 12 3 4

            ^

            +-- continue searching here



Some Words 12 3 4

            ^^?

            next match, replace by "2"



...

share|improve this answer

edited 2 hours ago

answered 2 hours ago

HeinziHeinzi

123k38271408

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Wanted to explain, but it wasn't easy. Yours were the best explanation 👍
  
  – DMA
  2 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you for the detailed explanation !
  
  – nnty
  2 hours ago
  

  
  
  
  

add a comment | 

Regex.Replace continues to search after the previous match:

Some Words 1 2 3 4

           ^^^

         first match, replace by "12"



Some Words 12 3 4

             ^

             +-- continue searching here



Some Words 12 3 4

              ^^^

            next match, replace by "34"

You can use a zero-width positive lookahead assertion to avoid that:

string result = Regex.Replace(test, @"(d)s(?=d)", @"$1");

Now the final digit is not part of the match:

Some Words 1 2 3 4

           ^^?

         first match, replace by "1"



Some Words 12 3 4

            ^

            +-- continue searching here



Some Words 12 3 4

            ^^?

            next match, replace by "2"



...

share|improve this answer

edited 2 hours ago

answered 2 hours ago

HeinziHeinzi

123k38271408

Some Words 1 2 3 4

           ^^^

         first match, replace by "12"



Some Words 12 3 4

             ^

             +-- continue searching here



Some Words 12 3 4

              ^^^

            next match, replace by "34"

string result = Regex.Replace(test, @"(d)s(?=d)", @"$1");

Some Words 1 2 3 4

           ^^?

         first match, replace by "1"



Some Words 12 3 4

            ^

            +-- continue searching here



Some Words 12 3 4

            ^^?

            next match, replace by "2"



...

share|improve this answer

edited 2 hours ago

answered 2 hours ago

HeinziHeinzi

123k38271408

answered 2 hours ago

HeinziHeinzi

123k38271408

answered 2 hours ago

HeinziHeinzi

123k38271408

9

Your regex consumes the digit on the right. (d)s(d) matches and captures 1 in Some Words 1 2 3 4 into Group 1, then matches 1 whitespace, and then matches and consumes (i.e. adds to the match value and advances the regex index) 2. Then, the regex engine tries to find another match from the current index, that is already after 1 2. So, the regex does not match 2 3, but finds 3 4.

Here is your regex demo and a diagram showing that:

Also, see the process of matching here:

Use lookarounds instead that are non-consuming:

(?<=d)s+(?=d)

See the regex demo

Details

• 
  (?<=d) - a positive lookbehind that matches a location in string immediately preceded with a digit


• 
  s+ - 1+ whitespaces


• 
  (?=d) - a positive lookahead that matches a location in string immediately followed with a digit.

C# demo:

string test = "Some Words 1 2 3 4";

string result = Regex.Replace(test, @"(?<=d)s+(?=d)", "");

See the online demo:

var strs = new List<string> {"Some Words 1 2 3 4", "Some Words That Should not be replaced 12 9 123 4 12", "test 9 8", "t e s t 9 8", "Another 12 000" };

foreach (var test in strs) 

{

    Console.WriteLine(Regex.Replace(test, @"(?<=d)s+(?=d)", ""));

}

Output:

Some Words 1234

Some Words That Should not be replaced 129123412

test 98

t e s t 98

Another 12000

share|improve this answer

edited 52 mins ago

answered 2 hours ago

Wiktor StribiżewWiktor Stribiżew

319k16139221

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you ! Good answer, but @heinzi 's explanation was a little bit more clearer. Therefore I accepted his answer.
  
  – nnty
  2 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @nnty Ok, just in case, I added diagrams.
  
  – Wiktor Stribiżew
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @nnty I hope the animation showing how your regex works is fine.
  
  – Wiktor Stribiżew
  52 mins ago
  

  
  
  
  

add a comment | 

9

Your regex consumes the digit on the right. (d)s(d) matches and captures 1 in Some Words 1 2 3 4 into Group 1, then matches 1 whitespace, and then matches and consumes (i.e. adds to the match value and advances the regex index) 2. Then, the regex engine tries to find another match from the current index, that is already after 1 2. So, the regex does not match 2 3, but finds 3 4.

Here is your regex demo and a diagram showing that:

Also, see the process of matching here:

Use lookarounds instead that are non-consuming:

(?<=d)s+(?=d)

See the regex demo

Details

• 
  (?<=d) - a positive lookbehind that matches a location in string immediately preceded with a digit


• 
  s+ - 1+ whitespaces


• 
  (?=d) - a positive lookahead that matches a location in string immediately followed with a digit.

C# demo:

string test = "Some Words 1 2 3 4";

string result = Regex.Replace(test, @"(?<=d)s+(?=d)", "");

See the online demo:

var strs = new List<string> {"Some Words 1 2 3 4", "Some Words That Should not be replaced 12 9 123 4 12", "test 9 8", "t e s t 9 8", "Another 12 000" };

foreach (var test in strs) 

{

    Console.WriteLine(Regex.Replace(test, @"(?<=d)s+(?=d)", ""));

}

Output:

Some Words 1234

Some Words That Should not be replaced 129123412

test 98

t e s t 98

Another 12000

share|improve this answer

edited 52 mins ago

answered 2 hours ago

Wiktor StribiżewWiktor Stribiżew

319k16139221

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thank you ! Good answer, but @heinzi 's explanation was a little bit more clearer. Therefore I accepted his answer.
  
  – nnty
  2 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @nnty Ok, just in case, I added diagrams.
  
  – Wiktor Stribiżew
  1 hour ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @nnty I hope the animation showing how your regex works is fine.
  
  – Wiktor Stribiżew
  52 mins ago
  

  
  
  
  

add a comment | 

Your regex consumes the digit on the right. (d)s(d) matches and captures 1 in Some Words 1 2 3 4 into Group 1, then matches 1 whitespace, and then matches and consumes (i.e. adds to the match value and advances the regex index) 2. Then, the regex engine tries to find another match from the current index, that is already after 1 2. So, the regex does not match 2 3, but finds 3 4.

Here is your regex demo and a diagram showing that:

Also, see the process of matching here:

Use lookarounds instead that are non-consuming:

(?<=d)s+(?=d)

See the regex demo

Details

• 
  (?<=d) - a positive lookbehind that matches a location in string immediately preceded with a digit


• 
  s+ - 1+ whitespaces


• 
  (?=d) - a positive lookahead that matches a location in string immediately followed with a digit.

C# demo:

string test = "Some Words 1 2 3 4";

string result = Regex.Replace(test, @"(?<=d)s+(?=d)", "");

See the online demo:

var strs = new List<string> {"Some Words 1 2 3 4", "Some Words That Should not be replaced 12 9 123 4 12", "test 9 8", "t e s t 9 8", "Another 12 000" };

foreach (var test in strs) 

{

    Console.WriteLine(Regex.Replace(test, @"(?<=d)s+(?=d)", ""));

}

Output:

Some Words 1234

Some Words That Should not be replaced 129123412

test 98

t e s t 98

Another 12000

share|improve this answer

edited 52 mins ago

answered 2 hours ago

Wiktor StribiżewWiktor Stribiżew

319k16139221

(?<=d)s+(?=d)

string test = "Some Words 1 2 3 4";

string result = Regex.Replace(test, @"(?<=d)s+(?=d)", "");

var strs = new List<string> {"Some Words 1 2 3 4", "Some Words That Should not be replaced 12 9 123 4 12", "test 9 8", "t e s t 9 8", "Another 12 000" };

foreach (var test in strs) 

{

    Console.WriteLine(Regex.Replace(test, @"(?<=d)s+(?=d)", ""));

}

Some Words 1234

Some Words That Should not be replaced 129123412

test 98

t e s t 98

Another 12000

share|improve this answer

edited 52 mins ago

answered 2 hours ago

Wiktor StribiżewWiktor Stribiżew

319k16139221

answered 2 hours ago

Wiktor StribiżewWiktor Stribiżew

319k16139221

answered 2 hours ago

Wiktor StribiżewWiktor Stribiżew

319k16139221