C++ String.Replace - no overloaded function takes 2 arguments? [duplicate]

I am trying to write a program that compresses text. For example, it would change aaaa to a^4.

For whatever reason, my compiler thinks that I am trying to overload a function when I am not. Here is my code (I apologize if it's long):

Code:

#include <iostream> #include <string> using namespace std; string compress(string str); int main() { string input; string str = "gggxxx"; cout << str; cout << compress(str); cin >> input; } string compress(string str) { //Adds space to the end and front of a string str = " " + str + " "; string final = str; int repeatingcharnum = 0; char relavantchar = ' '; string replacestr = ""; string placeholder = ""; bool flag = false; for (int i = 1; i < str.length(); i++) { char lastchar = str[i - 1]; char currentchar = str[i]; if (lastchar == currentchar) { relavantchar = currentchar; repeatingcharnum++; flag = true; } else if (lastchar != currentchar && flag) { flag = false; //cout << repeatingcharnum << endl; //cout << "relavant:" <<relavantchar << endl; string replacestr = ""; for (int x = 0; x < repeatingcharnum; x++) { replacestr += relavantchar; } placeholder = relavantchar + "^" + repeatingcharnum; final.replace(replacestr, placeholder); replacestr = ""; placeholder = ""; repeatingcharnum = 0; relavantchar = ' '; } } return final; } 

Output:

1>------ Build started: Project: Compression, Configuration: Debug Win32 ------ 1>Compression.cpp 1>C:\Users\Admin\source\repos\Compression\Compression\Compression.cpp(27,23): warning C4018: '<': signed/unsigned mismatch 1>C:\Users\Admin\source\repos\Compression\Compression\Compression.cpp(47,50): error C2661: 'std::basic_string<char,std::char_traits<char>,std::allocator<char>>::replace': no overloaded function takes 2 arguments 1>Done building project "Compression.vcxproj" -- FAILED. ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== 

I am programming in C++ using Visual Studio 2019 Community Edition.