c++ string class concantenate

[tommyo]

I can't figure out how to write this ConCatenation member function for my Mystring class. I need it to ConCat Mystring s onto the tail end of another Mystring (stored in sval).

The error i get "Control reaches end of non void function"
sval stores the string values
slen stores the string length



Mystring Mystring :: ConCat(Mystring s){
for(int i= 0; s.sval[i] <= s.slen; i++){
sval[slen + 1] = s.sval[i];
}

}


---------------------------------------

  #include <iostream>
using namespace std;


class Mystring{
    private:
        char sval[100];
        int slen;
    public:
    //constructors
    Mystring(): slen(0){}
    Mystring(char s[]);
    
    //access functions
    bool EqualTo(Mystring s);
    bool GreaterThan(Mystring s);
    bool LessThan(Mystring s);
    int Length();
    Mystring ConCat(Mystring s);

    
    //modifier funtions
    char& At(int pos);
    void Reverse();
    void ToLowercase();
    void ToUppercase();
    
    //input & output functions
    void Read();
    void Write();
    
    //tools
    bool IsPalindrome();
    
};

bool go = true;
int inputcount = 0;
bool IsPalindrome(char s[]);


int main(){
    Mystring object[100];
    Mystring y_n_object[100];
    int inputcount = 0;
    //object[inputcount];   //create object? Or is object already created?
    //y_n_object[inputcount];  //create object? Or is object already created?
    
    
    cout << "Do you want to input a String? ('Yes' or 'No')" << ": ";
    y_n_object[inputcount].Read();               // cin.getline(yes_no, MAX2);
    
    y_n_object[inputcount].ToLowercase();
    
    
    do{
      if(y_n_object[inputcount].EqualTo(Mystring("n")))
            go = false;
        
       else if(y_n_object[inputcount].EqualTo(Mystring("yes")))
        {
            cout << "Please Enter String" << ": ";
            object[inputcount].Read();
            ++inputcount;
            
            
            cout << "Do you want to input another String (Yes or No)" ;
            y_n_object[inputcount].Read();
            
            y_n_object[inputcount].ToLowercase();
        
        }
        
        else{
            cout << "Please enter a valid response - Either 'Yes' or 'No':";
            y_n_object[inputcount].Read();
            
            y_n_object[inputcount].ToLowercase();
        }
        
    }
    
    while (go);
    
    
               
    cout << endl << "There are a total of " << inputcount << " " << "strings input";
    cout << endl;
    
               
    for(int i = 0; i < inputcount; i++){
        if(object[i].IsPalindrome()){
            object[i].ConCat(Mystring("   Plaindrome"));
            object[i].Write();
               cout << endl;
        }
        else
            object[i].Write();
            cout << endl;
        
  }
    
    return 0;
    
}

               
               
//string class constructors

Mystring :: Mystring(char s[])
{
    for (slen=0; s[slen] && (slen < 100); slen++)
    sval[slen] = s[slen];
}





//String class access functions

int Mystring:: Length(){   //Is correct
    
    return slen;
}


bool Mystring:: EqualTo(Mystring s){
    if ( slen != s.slen)
        return false;
    
    for(int i = 0; i<slen && sval[i] == s.sval[i]; i++){
        if( i == slen)
            return true;
    }
    
    return false;
}

bool Mystring:: GreaterThan(Mystring s){
    for(int i = 0;  i < slen; i++){
        if (s.sval[i] > sval[i])
            return true;
    
        else if(s.sval[i] < sval[i])
        return false;
    }
    
    if(s.sval[slen] > sval[slen])
        return true;
    
    
    return false;
}
                                                 //if both strings are the same but one is a char longer, watch out for this.
 
bool Mystring:: LessThan(Mystring s){
        for(int i = 0;  i < slen; i++){
            if (s.sval[i] < sval[i])
                return true;
            
            else if(s.sval[i] > sval[i])
                return false;
        }
    
            if(s.sval[slen] < sval[slen])
                return true;
                
                      
           return false;
}                                              //what is wrong with this?


Mystring Mystring :: ConCat(Mystring s){
    for(int i= 0; s.sval[i] <= s.slen; i++){
        sval[slen+1] = s.sval[i];
    }
    
}                                                   //what is wrong with this?

 
//modifier functions
    char& Mystring :: At(int pos){    //Is Correct
    
    return (pos < slen) ? sval[pos] : sval[slen-1];
}

    void Mystring :: ToLowercase(){
        for(int i = 0; sval[i] != '\0'; i++ )
            if((sval[i] >='A') && (sval[i] <= 'Z'))
                sval[i] += 32;
}

    void Mystring :: ToUppercase(){
        for(int i = 0; sval[i] != '\0'; i++ )
            if((sval[i] >='a') && (sval[i] <= 'A'))
                sval[i] -= 32;
    }
    
    
    void Mystring:: Reverse(){
        char temp[100];
        for(int i = 0; i < slen; i++){
            temp[i] = sval[i];
            sval[i] = sval[slen];
            sval[slen] = temp[i];
            slen--;
    }
            }
//input/output functions
void Mystring:: Read(){
    char input_string[101];
    
    cin >> input_string;
    for(slen=0; input_string[slen] && (slen<100); slen++)
        sval[slen] = input_string[slen];
}

void Mystring:: Write(){
    for (int i = 0; i < slen; i++)
        cout << sval[i];
}
    

bool Mystring:: IsPalindrome(){
    
        int leftpos = 0;
        int rightpos = slen;
        
        for( ; sval[leftpos] == sval[rightpos] && leftpos < rightpos; leftpos++, rightpos--)
        {
            while(sval[leftpos] == ' ')
                ++leftpos;
            
            while(sval[rightpos] == ' ')
                --rightpos;
            
            if(sval[leftpos] != sval[rightpos])
                return false;
            
        }

        return true;
}

[kevinkjt2000]

Your ConCat method is missing a return statement. The return type appears to be Mystring.

[ats15]

Your function is supposed to return a Mystring. Probably you want to add return *this;