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I am trying to replace phrases in a text, but I tried to run this c++ program, but this deletes all the string after the replaced one, so I can't continue replacing different texts using this function. for example: input is hellookyou and the output is hellohello. the "you" part is missing. could you please explain why it is missing and what I should do. Thanks in advance

//edited this header part, and altered some of the code so that it is buildable #include <iostream> #include <conio.h>// for getch() function std::string replaceOK(std::string a){ char ok[] = "ok"; while(a.find(ok, 0) < a.length()){ a.replace(a.find(ok, 0), a.length() - a.find(ok, 3),"hello"); } return a; } int main(){ std::string a; std::cin >> a; a = replaceOK(a); std::cout << a << std::endl; return 0; }

Fixed code. This won't work if it has the same phrase that I want to change in the resulting changed phrase. It will loop on endlessly.

 #include <iostream> #include <conio.h>// for getch() function std::string replaceOK(std::string a){ char ok[] = "ok"; while(a.find(ok, 0) < a.length()){ std::cout << "1"; // for visualization of the loop. a.replace(a.find(ok, 0), a.length() - a.find(ok, 3),"ok1"); // changed "hello" to "ok1" } return a; } int main(){ std::string a; std::cin >> a; a = replaceOK(a); std::cout << a << std::endl; return 0; }
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    What are you doing with the modified string that replaceOK returns? Commented Mar 30, 2021 at 5:00
  • nothing in this code snippet just cout it. in the real program it writes the modified version into a file. Commented Mar 30, 2021 at 5:05
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    Please edit your question to show us a proper minimal reproducible example. One that only exhibits the problem you're asking about and nothing more (the shown code will not build). Commented Mar 30, 2021 at 5:06
  • Also, please take some time to think about the difference between passing arguments by value or by reference. Commented Mar 30, 2021 at 5:07
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    a.length() - a.find(ok, 3) what is it intended to do? Why not the constant 2? Commented Mar 30, 2021 at 5:07

1 Answer 1

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The problem lies in the way you are using the a.replace() function. The replace() function works in the way a.replace(0,3,"red") This would change 3 characters from the 0th index and replace them with the string "red".

So in you case you are going to the index where you encounter the first occurence of "ok" string using a.find("ok",0), then by using a.length()-a.find("ok",3), you are getting 5 as the value and replacing them with "hello".

So you are basically doing a.replace(5,5,"hello"). Because of this the "okyou" part gets replaced by "hello" string.

The code is here:

#include <iostream> #include <conio.h>// for getch() function using namespace std; string replaceOK(string a){ string ok = "ok"; int n=a.find("ok",0); int p=1;//for counting the number of occurence of "ok" while(n < a.length()){ if(p==1) a.replace(n,ok.size(),"hello"); //replace 1st occurence of ok to hello if(p==3) a.replace(n,ok.size(),"ok1"); //replace 3rd occurence of ok to ok1 if(n+2>=a.length()) break; n=a.find("ok",n+2); p+=1; } return a; } int main(){ string a; cin >> a; a = replaceOK(a); cout << a << std::endl; return 0; }
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4 Comments

thanks. It helped with the first code, but the second one, it just kind of looped through endlessly. is there a way to fix that?(I edited the question so pls take a look.)
So you want to replace different instances of "ok" with different strings Is that so?
yes. that is what I'm trying to do. but sometimes, there's the same phrase as the replaced phrase in the phrase that I want to change it into. I hope you got that last sentence.....
Okay. Now I understood what you want. I have edited my answer and uploaded the code there. Now you can store the pth occurrence in the variable 'p' and then replace whichever occurrence you want with the word of your choice. You can create a function for that also. Hope it helps

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