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//This is the definition for the class StringVar
//whose values are strings. An object is declared as follows.
//Note that you use (max_size), not [max_size]
//StringVar the_object(max_size);
//where max_size is the longest string length allowed.
#include<iostream>
using namespace std;
#include<fstream>
class StringVar
{
public:
StringVar(int size);
//Initializes the object so it can accept string values up to size
//in length. Sets the value of the object equal to the empty string.
StringVar( );
//Initializes the object so it can accept string values of length 100
//or less. Sets the value of the object equal to the empty string.
StringVar(const char a[]);
//Precondition: The array a contains characters terminated with '\0'.
//Initializes the object so its value is the string stored in a and
//so that it can later be set to string values up to strlen(a) in length.
StringVar(const StringVar& string_object);
//Copy constructor.
~StringVar( );
//Returns all the dynamic memory used by the object to the freestore.
int length( ) const;
//Returns the length of the current string value.
void input_line(istream& ins);
//Precondition: If ins is a file input stream, then ins has been
//connected to a file.
//Action: The next text in the input stream ins, up to '\n', is copied
//to the calling object. If there is not sufficient room, then
//only as much as will fit is copied.
friend ostream& operator <<(ostream& outs, const StringVar& the_string);
//Overloads the << operator so it can be used to output values
//of type StringVar
//Precondition: If outs is a file output stream, then outs
//has already been connected to a file.
void operator=(const StringVar& right_side);
//Overloads the assignment operator= to copy a string
//form one object to another.
void conversation(int max_name_size);
private:
char *value; //pointer to dynamic array that holds the string value.
int max_length; //declared max length of any string value.
};
//This is the implementation of the class StringVar.
//The definition for the class StringVar is in Display 11.11.
#include <cstdlib>
#include <cstddef>
#include <cstring>
//Uses cstddef and cstdlib:
StringVar::StringVar(int size) : max_length(size)
{
value = new char[max_length + 1];//+1 is for '\0'.
value[0] = '\0';
}
//Uses cstddef and cstdlib:
StringVar::StringVar( ) : max_length(100)
{
value = new char[max_length + 1];//+1 is for '\0'.
value[0] = '\0';
}
//Uses cstring, cstddef, and cstdlib:
StringVar::StringVar(const char a[]) : max_length(strlen(a))
{
value = new char[max_length + 1];//+1 is for '\0'.
strcpy(value, a);
}
//Uses cstring, cstddef, and cstdlib:
StringVar::StringVar(const StringVar& string_object)
: max_length(string_object.length( ))
{
value = new char[max_length + 1];//+1 is for '\0'.
strcpy(value, string_object.value);
}
StringVar::~StringVar( )
{
delete [] value;
}
//Uses cstring:
int StringVar::length( ) const
{
return strlen(value);
}
//Uses iostream:
void StringVar::input_line(istream& ins)
{
ins.getline(value, max_length + 1);
}
//Uses iostream:
ostream& operator <<(ostream& outs, const StringVar& the_string)
{
outs << the_string.value;
return outs;
}
void StringVar::operator=(const StringVar& right_side)
{
int new_length = strlen(right_side.value);
if(new_length > max_length)
{
delete [] value;
max_length = new_length;
value = new char[max_length + 1];
}
for (int i = 0; i < new_length; i++)
value[i] = right_side.value[i];
value[new_length] = '\0';
}
#include <iostream>
using namespace std;
int main( )
{
conversation(30);
cout << "End of demonstration.\n";
return 0;
}
//This is only a demonstration function:
void conversation(int max_name_size)
{
using namespace std;
StringVar your_name(max_name_size), our_name("Borg");
cout << "What is your name?\n";
your_name.input_line(cin);
cout << "We are " << our_name << endl;
cout << "We will meet again " << your_name << endl;
}
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