problems with >> istream overloading

Though I managed to get the program too compile I still have a runtime error. The program crashes after I enter my name.

here is stringm.cpp

Code:

#include <stdlib.h>
#include "stringh.hpp"

int main()
{
    String s1(" and I am a C++ student.");
    String s2="Please enter your name: ";
    String s3;
    cout << s2;
    cin >> s3;
    s2="My name is "+s3;
    cout << s2 << ".\n";
    s2=s2+s1; // overloaded =, + operators
    s2.stringup();// convert to upper case
    cout << "The string\n" << s2 << "\ncontains" <<s2.has('A')
         << " 'A' chachters in it.\n";
    s1="red";  
    String rgb[3]={String(s1), String("green"), String("blue")};
    cout << "Enter the name of a primary color for mixing light: ";
    String ans;
    bool success=false;
    while (cin>>ans)
    {
          ans.stringlow();  //convert to lower case
          for (int i=0;i<3;i++)
          {
              if (ans==rgb[i])
              {
                 cout << "That's right!\n";
                 success=true;
                 break;
              }
          }
          if (success)
             break;
          else
              cout << "Try again!\n";
    }
    cout << "Bye!\n";
    system("PAUSE");
    return 0;
}

here is the header

Code:

//string prblm 2 pg 537 C++ Primer plus Third Edition
#ifndef _STRINGH_HPP_
#define _STRINGH_HPP_
#include <iostream>
using namespace std;

class String
{
      private:
              char * str;
              int len;
      public:
             // constructor
             String(const char * s);
             String();
             // copy constructor
             String(const String & st);
             //destructor
             ~String();
             // inline function
             int length() const {return len;}
             
             void stringup(); //{str=strupr(str);} string.h
             void stringlow(); //{str=strlwr(str);}
             
             int has(char s);// count chars 
             // overloaded operators
             String & operator=(const String & st);  
             String & operator=(const char * s);
             //friend functions
             friend String operator+(String & str1,const String &str2);
             friend String operator+(char * s,String &str2);
             friend bool operator>(const String &str1,const String &str2);
             friend bool operator<(const String &str1,const String &str2);
             friend bool operator==(const String &str1,const String &str2);
             friend ostream & operator<<(ostream & os, const String & st);
             friend istream & operator>>(istream & is, String & st);
};
#endif

here is the function definitons

Code:

//string prblm 2 pg 537 C++ Primer plus Third Edition
#include <iostream>
#include <cstring>
#include <cctype>
using namespace std;
#include "stringh.hpp"

//class methods
String::String(const char*s) // make String from c string
{
       len=strlen(s);
       str=new char[len+1];
       strcpy(str,s);
}

String::String()
{
       len=0;
       str = new char[1];
       str[0]='\0';
}

String::String(const String & st) // copy constructor
{
       len=st.len;
       str=new char[len+1];
       strcpy(str,st.str);
}

String::~String()
{
       delete [] str;
}
void String::stringup()
{
     for ( int x = 0; x < strlen (str); x++ )
           str[x] = toupper ( str[x] );
}

void String::stringlow()
{
     for ( int x = 0; x < strlen (str); x++ )
           str[x] = tolower ( str[x] );
}
int String::has(char s)
{
    int c=0;
    for (int i=0; i<strlen(str); i++)
        if (str[i]==s)
           c++;
    return c;
}

// assign String to a String
String & String::operator=(const String & st)
{
       if (this==&st)
          return *this;
       delete [] str;
       len=st.len;
       str=new char[len+1];
       strcpy(str,st.str);
       return *this;
}

// assign a C string to a String
String & String::operator=(const char * s)
{
       delete [] str;
       len = strlen(s);
       str=new char[len+1];
       strcpy(str,s);
       return *this;
}

//concatinate two strings
String operator+(String &str1,const String &str2)
{      
       int size=str1.len+str2.len+1;
       char * temp=new char[str1.len+1];
       strcpy(temp,str1.str);
       //resize str1.str to hold concatenate string
       delete [] str1.str;
       str1.str=new char[size];
       strcpy(str1.str,temp);
       delete [] temp;
       strcat(str1.str,str2.str);
       return str1;
}

String operator+(char * s,String &str2)
{
       int size=str2.len+strlen(s)+1;
       char * temp=new char[str2.len+1];
       strcpy(temp,str2.str);
       //resize str1.str to hold concatenate string
       delete [] str2.str;
       str2.str=new char[size];
       strcpy(str2.str,temp);
       delete [] temp;
       str2.str=strcat(s,str2.str);
       return str2;
}

// true if st1 preceds st2 in collating sequence
bool operator<(const String &st1, const String &st2)
{
     if (strcmp(st1.str,st2.str)<0)
        return true;
     else 
          return false;
}

// true if st1 same as st2 
bool operator==(const String &st1, const String &st2)
{
     if (strcmp(st1.str,st2.str)==0)
        return true;
     else 
          return false;
}

//display String
ostream & operator<<(ostream & os,const String & st)
{
        os << st.str;
        return os;
}

istream & operator>>(istream & is, String & st)
{
        char temp[80];
        is.get(temp,80);
        if (is)
           st=temp;
        while (is && is.get() != '\n')
              continue;
        return is;
}

I know this is a lot of code I suspect there is an error in the 2nd overloaded + operator used to concat the strings please help.

double posting will not help you. please delete this thread.

I posted on the C board by accident.
It has been moved here.

I manage to get my program to compile I will edit my post with the complete source because my prog crashes right after I enter the name. Hopefully someone can help.

here is another update to the second operator+ function

Code:

String operator+(char * s,String &str2)
{
       int size=str2.len+strlen(s)+1;
       char * temp=new char[str2.len+1];
       strcpy(temp,str2.str);
       //resize str2.str to hold concatenate string
       delete [] str2.str;
       str2.str=new char[size];
       str2.str=strcat(s,temp);
       delete [] temp;
       return str2;
}

I guess i should edit the subject of this post too.

I managed to correct the problem on my own, wich is usually more rewarding
here is a simple solution for the second operator+
maybe this will help someone else

Code:

String operator+(char * s,String &str2)
{      
       String temp(s);
       str2=temp+str2; uses previous overloaded + operator      
       return str2;
}