Question

Help C++

Write a string class. To avoid conflicts with other similarly named classes, we will call our version MyString. This object is designed to make working with sequences of characters a little more convenient and less error-prone than handling raw c-strings, (although it will be implemented as a c-string behind the scenes). The MyString class will handle constructing strings, reading/printing, and accessing characters. In addition, the MyString object will have the ability to make a full deep-copy of itself when copied.

Your class must have only one data member, a c-string implemented as a dynamic array. In particular, you must not use a data member to keep track of the size or length of the MyString.

This is the first part of a two part assignment. In the next assignment you will be making some refinements to the class that you create in this assignment. For example, no documentation is required this week, but full documentation will be required next week.

Here is a list of the operations this class must support:

• A length member function that returns the number of characters in the string. Use strlen().

• Construction of a MyString from a const c-string. You should copy the string data, not just store a pointer to an argument passed to the constructor. Constructing a MyString with no arguments creates an empty MyString object (i.e. ""). A MyString object should be implemented efficiently (space-wise) which is to say you should not have a fixed-size buffer of chars, but instead allocate space for chars on an as-needed basis. Use strcpy().

• Printing a MyString to a stream using an overloaded << (insertion) operator, which should simply print out its characters. Use <<.

• Your MyString object should overload the square brackets [ ] operator to allow direct access to the individual characters of the string. This operation should range-check and assert if the index is out of bounds. You will write two versions of the [ ] operator, a const version that allows read access to the chars, and a non-const version that returns the client a reference to the char so they can change the value.

• All six of the relational operators (<, <=, >, >=, ==, !=) should be supported. They should be able to compare MyString objects to other MyStrings as well as MyStrings to c-strings. The ordering will be based on ASCII values. You can think of this as essentially alphabetical order; however, because of the way that ASCII values are defined, uppercase letters will always come before lowercase letters, and punctuation will make things even more complicated. Confused? You don't need to worry about any of this: just use the results of calling the strcmp() function. MyStrings or c-strings should be able to appear on either side of the comparison operator.

• Don't forget to include the big-3.

You may use all of the c-string functionality provided by C++. This will include the strlen(), strcmp(), and strcpy() functions, along with the overloaded insertion operator for c-strings. These functions are all covered in detail in the text. When you use strcpy() treat it as a void function despite the fact that it has a return value. Do not use strncpy(), strncat(), or strncmp() since they are not implemented in all versions of C++. You may NOT use anything from the C++ string class!!

Unfortunately, Visual C++ will, under its default settings, report an error when you try to use strcpy() or strcat(), even though they are standard C++. You can prevent this by adding this line as the first line in your file:

#pragma warning(disable:4996)

You must place your header file and implementation file in a namespace. Normally one would call a namespace something more likely to be unique, but for purposes of convenience we will call our namespace "cs_mystring".

Client Program:

/* 
 * These functions are designed to help you test your MyString objects, 
 * as well as show the client usage of the class.
 *
 * The BasicTest function builds an array of strings using various
 * constructor options and prints them out.  It also uses the String
 * stream operations to read some strings from a data file.
 *
 * The RelationTest function checks out the basic relational operations
 * (==, !=, <, etc) on Strings and char *s.
 *
 *
 * The CopyTest tries out the copy constructor and assignment operators
 * to make sure they do a true deep copy.
 *
 * Although not exhaustive, these tests will help you to exercise the basic
 * functionality of the class and show you how a client might use it.
 *
 * While you are developing your MyString class, you might find it
 * easier to comment out functions you are ready for, so that you don't
 * get lots of compile/link complaints.
*/
 
#include "mystring.h"
#include <cctype>      // for toupper()
#include <iostream>
#include <string>
using namespace std;
using namespace cs_mystring;

void BasicTest();
void RelationTest();
void CopyTest();
MyString AppendTest(const MyString& ref, MyString val);
string boolString(bool convertMe);

int main()
{
    BasicTest();
    RelationTest();
    CopyTest();
}





void BasicTest()
{
    MyString s;
    cout << "----- Testing basic String creation & printing" << endl;
    
    const MyString strs[] = 
                {MyString("Wow"), MyString("C++ is neat!"),
                 MyString(""), MyString("a-z")};
                         
    for (int i = 0; i < 4; i++){
        cout << "string [" << i <<"] = " << strs[i] << endl;
    }

    cout << endl << "----- Testing access to characters (using const)" << endl;
    const MyString s1("abcdefghijklmnopqsrtuvwxyz");
    cout <<  "Whole string is " << s1 << endl;
    cout << "now char by char: ";
    for (int i = 0; i < s1.length(); i++){
        cout << s1[i];
    }

    cout << endl << "----- Testing access to characters (using non-const)" << endl;
    MyString s2("abcdefghijklmnopqsrtuvwxyz");
    cout <<  "Start with " << s2;
    for (int i = 0; i < s2.length(); i++){
        s2[i] = toupper(s2[i]);
    }
    cout << " and convert to " << s2 << endl;
}





string boolString(bool convertMe) {
    if (convertMe) {
        return "true";
    } else {
        return "false";
    }
}





void RelationTest()
{
    cout << "\n----- Testing relational operators between MyStrings\n";

    const MyString strs[] = 
        {MyString("app"), MyString("apple"), MyString(""), 
        MyString("Banana"), MyString("Banana")};

    for (int i = 0; i < 4; i++) {
        cout << "Comparing " << strs[i] << " to " << strs[i+1] << endl;
        cout << "    Is left < right? " << boolString(strs[i] < strs[i+1]) << endl;
        cout << "    Is left <= right? " << boolString(strs[i] <= strs[i+1]) << endl;
        cout << "    Is left > right? " << boolString(strs[i] > strs[i+1]) << endl;
        cout << "    Is left >= right? " << boolString(strs[i] >= strs[i+1]) << endl;
        cout << "    Does left == right? " << boolString(strs[i] == strs[i+1]) << endl;
        cout << "    Does left != right ? " << boolString(strs[i] != strs[i+1]) << endl;
    }
 
    cout << "\n----- Testing relations between MyStrings and char *\n";
    MyString s("he");
    const char *t = "hello";
    cout << "Comparing " << s << " to " << t << endl;
    cout << "    Is left < right? " << boolString(s < t) << endl;
    cout << "    Is left <= right? " << boolString(s <= t) << endl;
    cout << "    Is left > right? " << boolString(s > t) << endl;
    cout << "    Is left >= right? " << boolString(s >= t) << endl;
    cout << "    Does left == right? " << boolString(s == t) << endl;
    cout << "    Does left != right ? " << boolString(s != t) << endl;
    
    MyString u("wackity");
    const char *v = "why";
    cout << "Comparing " << v << " to " << u << endl;
    cout << "    Is left < right? " << boolString(v < u) << endl;
    cout << "    Is left <= right? " << boolString(v <= u) << endl;
    cout << "    Is left > right? " << boolString(v > u) << endl;
    cout << "    Is left >= right? " << boolString(v >= u) << endl;
    cout << "    Does left == right? " << boolString(v == u) << endl;
    cout << "    Does left != right ? " << boolString(v != u) << endl;  
}





MyString AppendTest(const MyString& ref, MyString val)
{
    val[0] = 'B';
    return val;
}





void CopyTest()
{
    cout << "\n----- Testing copy constructor and operator= on MyStrings\n";

    MyString orig("cake");
    
    MyString copy(orig);    // invoke copy constructor

    copy[0] = 'f';  // change first letter of the *copy*
    cout << "original is " << orig << ", copy is " << copy << endl;
    
    MyString copy2;      // makes an empty string
    
    copy2 = orig;        // invoke operator=
    copy2[0] = 'f';      // change first letter of the *copy*
    cout << "original is " << orig << ", copy is " << copy2 << endl;
    
    copy2 = "Copy Cat";
    copy2 = copy2;        // copy onto self and see what happens
    cout << "after self assignment, copy is " << copy2 << endl;
    
    cout << "Testing pass & return MyStrings by value and ref" << endl;
    MyString val = "winky";
    MyString sum = AppendTest("Boo", val);
    cout << "after calling Append, sum is " << sum << endl;
    cout << "val is " << val << endl;
    val = sum;
    cout << "after assign,  val is " << val << endl;
}

Correct Output:

----- Testing basic String creation & printing
string [0] = Wow
string [1] = C++ is neat!
string [2] = 
string [3] = a-z

----- Testing access to characters (using const)
Whole string is abcdefghijklmnopqsrtuvwxyz
now char by char: abcdefghijklmnopqsrtuvwxyz
----- Testing access to characters (using non-const)
Start with abcdefghijklmnopqsrtuvwxyz and convert to ABCDEFGHIJKLMNOPQSRTUVWXYZ

----- Testing relational operators between MyStrings
Comparing app to apple
    Is left < right? true
    Is left <= right? true
    Is left > right? false
    Is left >= right? false
    Does left == right? false
    Does left != right ? true
Comparing apple to 
    Is left < right? false
    Is left <= right? false
    Is left > right? true
    Is left >= right? true
    Does left == right? false
    Does left != right ? true
Comparing  to Banana
    Is left < right? true
    Is left <= right? true
    Is left > right? false
    Is left >= right? false
    Does left == right? false
    Does left != right ? true
Comparing Banana to Banana
    Is left < right? false
    Is left <= right? true
    Is left > right? false
    Is left >= right? true
    Does left == right? true
    Does left != right ? false

----- Testing relations between MyStrings and char *
Comparing he to hello
    Is left < right? true
    Is left <= right? true
    Is left > right? false
    Is left >= right? false
    Does left == right? false
    Does left != right ? true
Comparing why to wackity
    Is left < right? false
    Is left <= right? false
    Is left > right? true
    Is left >= right? true
    Does left == right? false
    Does left != right ? true

----- Testing copy constructor and operator= on MyStrings
original is cake, copy is fake
original is cake, copy is fake
after self assignment, copy is Copy Cat
Testing pass & return MyStrings by value and ref
after calling Append, sum is Binky
val is winky
after assign,  val is Binky

Answer 1

CODE STRING:

#include <iostream>

using namespace std;

#ifndef _MYSTRING_H_
#define _MYSTRING_H_

class myString{
private:
   char *str;
public:
   myString();
   myString(const char *s);
   void operator = (myString &s);
   int length();
   friend ostream &operator <<(ostream &out, myString &s);
   friend istream &operator >>(istream &out, myString &s);
   bool operator <(myString &s);
   bool operator <=(myString &s);
   bool operator >(myString &s);
   bool operator >=(myString &s);
   bool operator ==(myString &s);
   bool operator !=(myString &s);
};

#endif

$\color{blue}\underline{myString.cpp:}$

#include "myString.h"
#include <cstring>

myString::myString(){
   str = new char;
   str[0] = '\0';
}

myString::myString(const char *s){
   int len = strlen(s);
   str = new char[len + 1];
   for(int i = 0; i < len; ++i){
       str[i] = s[i];
   }
   str[len] = '\0';
}

void myString::operator = (myString &s){
   s.str = new char[length() + 1];
   for(int i = 0; i < length(); ++i){
       s.str[i] = str[i];
   }
   s.str[length()] = '\0';
}

int myString::length(){
   return strlen(str);
}

ostream &operator <<(ostream &out, myString &s){
   out << s.str;
   return out;
}

istream &operator >>(istream &in, myString &s){
   in >> s.str;
   return in;
}

bool myString::operator < (myString &s){
   return strcmp(str, s.str) < 0;
}

bool myString::operator <= (myString &s){
   return strcmp(str, s.str) <= 0;
}

bool myString::operator > (myString &s){
   return strcmp(str, s.str) > 0;
}

bool myString::operator >= (myString &s){
   return strcmp(str, s.str) >= 0;
}

bool myString::operator == (myString &s){
   return strcmp(str, s.str) == 0;
}

bool myString::operator != (myString &s){
   return strcmp(str, s.str) != 0;
}

$\color{blue}\underline{main.cpp:}$

#include "myString.h"
#include <iostream>

using namespace std;

int main(){
   myString s1, s2;
   cout << "Enter first string: ";
   cin >> s1;
   cout << "Enter second string: ";
   cin >> s2;
   cout << "you entered: " << s1 << " and " << s2 << endl;
   myString s3 = s1;
   cout << "Value of s3 is " << s3 << endl;
   if(s1 < s2){
       cout << s1 << " < " << s2 << endl;
   }
   if(s1 <= s2){
       cout << s1 << " <= " << s2 << endl;
   }
   if(s1 > s2){
       cout << s1 << " > " << s2 << endl;
   }
   if(s1 >= s2){
       cout << s1 << " >= " << s2 << endl;
   }
   if(s1 == s2){
       cout << s1 << " == " << s2 << endl;
   }
   if(s1 != s2){
       cout << s1 << " != " << s2 << endl;
   }
   return 0;
}