Recursively replace chars in a string

[lesliebellamy]

This function recursively replaces every instance of the char "-" in the string "-h-e-l-l-o-", with the char " ". After running the code it gave me a segmentation error, which I'm not sure how to fix. I've included the function call along with the function. Can anyone help?

edit: I fixed the segmentation error, and the code runs, but I've run into another issue. The function doesn't replace '-' with ' '. The compiler just spits out 'h-e-l-l-o' with no modifications.

/****   Recursive string replace   > Replaces all instances of a character in a string with another character*****/
    void recReplace(string s2, int i, char old, char neW)
   { 
    if(s2[i] == old) //search for old char
      {
        i = neW; //replace it
        i++; //iterate i
        recReplace(s2, i, old, neW); //call function
       }
    else if(s2[i] == '\0')
      return;
   }
    
    /* Replaces a character in a string with a new one */    
        cout << "REPLACE" << endl;    
        cout << "----------" << endl;    
        string s2 = "-h-e-l-l-o-";    
        char oldChar = '-';    
        char newChar = ' ';   
        cout << "String: " << s2 << endl;    
        cout << "> Replace '" << oldChar << "' with '" << newChar << endl;    
        recReplace(s2, 0, oldChar, newChar);    
        cout << "String: " <<  s2 << endl;    
        cout << endl;    

[lastchance]

Pass s2 and i by reference, not by value, or neither will return changed values to the calling program. Set s2[i], not i, to neW.

Do you really want to do this by recursion? Also, checking for null termination is not such a natural thing to do with a std::string as with a c-string.

And neW is not a good name for a variable - it's asking for trouble as there is a rather important keyword "new".

[JLBorges]

std::string replace( std::string str, char old, char replace_with, std::size_t from_pos = 0 )
{
    if( from_pos < str.size() ) // if we have not reached the end of the string
    {
        // replace the char at position from_pos if it is equal to old
        if( str[from_pos] == old ) str[from_pos] = replace_with ;

        // recursively replace chars at later positions and return the result
        return replace( str, old, replace_with, from_pos+1 ) ;
    }

    else return str ; // reached the end of the string; return it unchanged
}

[seeplus]

Unless this is an exercise using recursion, this is an extremely inefficient way of doing this.