How to return a string from a C function

Question

This is a simple sample program    include  lt iostream gt   include  lt string gt   using namespace std   string replaceSubstring string  string  string    int main         string str1  str2  str3       cout  lt  lt   These are the strings     lt  lt  endl      cout  lt  lt   str1    the dog jumped over the fence     lt  lt  endl      cout  lt  lt   str2    the     lt  lt  endl      cout  lt  lt   str3    that     lt  lt  endl  lt  lt  endl      cout  lt  lt   This program will search str1 for str2 and replace it with str3 n n        cout  lt  lt   The new str1     lt  lt  replaceSubstring str1  str2  str3        cout  lt  lt  endl  lt  lt  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

User · Accepted Answer

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).
What happens if s2 is not part of s1? I'll leave it up to you to find how to fix that. Hint: std::string::npos ;)

User · Answer

Assign something to your strings  This will definitely help

User · Answer

string str1  str2  str3   cout  lt  lt   These are the strings     lt  lt  endl  cout  lt  lt   str1    the dog jumped over the fence     lt  lt  endl  cout  lt  lt   str2    the     lt  lt  endl  cout  lt  lt   str3    that     lt  lt  endl  lt  lt  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  lt  lt   These are the strings     lt  lt  endl  cout  lt  lt   str1       lt  lt  str1  lt  lt        lt  lt  endl  cout  lt  lt   str2       lt  lt  str2  lt  lt        lt  lt  endl  cout  lt  lt   str3       lt  lt  str3  lt  lt        lt  lt  endl  lt  lt  endl

[c++] How to return a string from a C++ function?

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