Stepping Up To C++

Listing 1 A simple string class

//
// String class with overloaded cat function
//

#include <iostream.h>
#include <string.h>

class String
   {
public:
   String(const char *);
   String(const String &);
   ~String()
       { delete [] str; }
   String &operator=(const String &);
   String &operator+=(const String &);
   size_t length()
       { return len; }
   operator const char *()
       { return str; }
   char &operator[](size_t i)
       { return str[i]; }
   // ...
private:
    size_t len;
    char *str;
    };

String::(const char *s)
    {
    len = strlen(s);
    str = strcpy(new char[len + 1], s);
    }

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

String &String::operator=(const String &s)
    {
    if (len != s.len)
       {
       char *p = new char[s.len + 1];
       strcpy(p, s.str);
       delete [] str;
       len = s.len;
       str = p;
       }
    return *this;
    }

String &String::operator+=(const String &s)
    {
    if (s.len > 0)
       {
       char *p = new char[len + s.len + 1];
       strcat(strcpy(p, str), s.str);
       delete [] str;
       len += s.len + 1;
       str = p;
       }
    return *this;
    }

String operator+(const String &s1, const String &s2)
    {
    String s = s1;
    return s += s2;
    }

// End of File