This is a simple sample program:
#include <iostream>
#include <string>
using namespace std;
string replaceSubstring(string, string, string);
int main()
{
string str1, str2, str3;
cout << "These are the strings: " << endl;
cout << "str1: \"the dog jumped over the fence\"" << endl;
cout << "str2: \"the\"" << endl;
cout << "str3: \"that\"" << endl << endl;
cout << "This program will search str1 for str2 and replace it with str3\n\n";
cout << "The new str1: " << replaceSubstring(str1, str2, str3);
cout << endl << endl;
}
string replaceSubstring(string s1, string s2, string s3)
{
int index = s1.find(s2, 0);
s1.replace(index, s2.length(), s3);
return s1;
}
It compiles however the function returns nothing. If I change return s1 to return "asdf" it will return asdf. How can I return a string with this function?
This question is related to
c++
string
return-value
You never give any value to your strings in main so they are empty, and thus obviously the function returns an empty string.
Replace:
string str1, str2, str3;
with:
string str1 = "the dog jumped over the fence";
string str2 = "the";
string str3 = "that";
Also, you have several problems in your replaceSubstring function:
int index = s1.find(s2, 0);
s1.replace(index, s2.length(), s3);
std::string::find returns a std::string::size_type (aka. size_t) not an int. Two differences: size_t is unsigned, and it's not necessarily the same size as an int depending on your platform (eg. on 64 bits Linux or Windows size_t is unsigned 64 bits while int is signed 32 bits).s2 is not part of s1? I'll leave it up to you to find how to fix that. Hint: std::string::npos ;)string str1, str2, str3;
cout << "These are the strings: " << endl;
cout << "str1: \"the dog jumped over the fence\"" << endl;
cout << "str2: \"the\"" << endl;
cout << "str3: \"that\"" << endl << endl;
From this, I see that you have not initialized str1, str2, or str3 to contain the values that you are printing. I might suggest doing so first:
string str1 = "the dog jumped over the fence",
str2 = "the",
str3 = "that";
cout << "These are the strings: " << endl;
cout << "str1: \"" << str1 << "\"" << endl;
cout << "str2: \"" << str2 << "\"" << endl;
cout << "str3: \"" << str3 << "\"" << endl << endl;
Assign something to your strings. This will definitely help.
Source: Stackoverflow.com