C++ Premier Plus 6th edition - Programming excercise - Chapter12 -2

string2.h

// string1.h -- fixed and augmented string class definition

#ifndef STRING1_H_
#define STRING1_H_
#include <iostream>
#include<cctype>

using std::ostream;
using std::istream;

class String
{
private:
    char * str;             // pointer to string
    int len;                // length of string
    static int num_strings; // number of objects
    static const int CINLIM = 80;  // cin input limit
public:
// constructors and other methods
    String(const char * s); // constructor
    String();               // default constructor
    String(const String &); // copy constructor

	// Newly added: Stringup(),Stringlow()
	void stringup();
	void stringlow();
	int has(char ch) const;

    ~String();              // destructor
    int length () const { return len; }
// overloaded operator methods    
    String & operator=(const String &);
    String & operator=(const char *);
    char & operator[](int i);
    const char & operator[](int i) const;
// overloaded operator friends
    friend bool operator<(const String &st, const String &st2);
    friend bool operator>(const String &st1, const String &st2);
    friend bool operator==(const String &st, const String &st2);
    friend ostream & operator<<(ostream & os, const String & st);
    friend istream & operator>>(istream & is, String & st);

	// overload operator+
	friend String operator+(const String&str1, const String& str2);
	friend String operator+(const char* s, const String& str2);
// static function
    static int HowMany();
};
#endif

string2.cpp

// string1.cpp -- String class methods
#include <cstring>                 // string.h for some
#include "string2.h"               // includes <iostream>
#include<cctype>

using std::cin;
using std::cout;

// initializing static class member

int String::num_strings = 0;

// static method
int String::HowMany()
{
    return num_strings;
}

// class methods
String::String(const char * s)     // construct String from C string
{
    len = std::strlen(s);          // set size
    str = new char[len + 1];       // allot storage
    strcpy_s(str,len+1,s);           // initialize pointer
    num_strings++;                 // set object count
}

String::String()                   // default constructor
{
    len = 4;
    str = new char[1];
    str[0] = '\0';                 // default string
    num_strings++;
}

String::String(const String & st)
{
    num_strings++;             // handle static member update
    len = st.len;              // same length
    str = new char [len + 1];  // allot space
    strcpy_s(str, len+1,st.str);  // copy string to new location
}

String::~String()                     // necessary destructor
{
    --num_strings;                    // required
    delete [] str;                    // required
}

// overloaded operator methods

// assign a 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_s(str,st.len+1, st.str);
    return *this;
}

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

// read-write char access for non-const String
char & String::operator[](int i)
{
    return str[i];
}

// read-only char access for const String
const char & String::operator[](int i) const
{
    return str[i];
}

// overloaded operator friends

bool operator<(const String &st1, const String &st2)
{
    return (std::strcmp(st1.str, st2.str) < 0);
}

bool operator>(const String &st1, const String &st2)
{
    return st2 < st1;
}

bool operator==(const String &st1, const String &st2)
{
    return (std::strcmp(st1.str, st2.str) == 0);
}

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

// quick and dirty String input
istream & operator>>(istream & is, String & st)
{
    char temp[String::CINLIM];
    is.get(temp, String::CINLIM);
    if (is)
        st = temp;
    while (is && is.get() != '\n')
        continue;
    return is;
}

/********************** Newly added ***********************/
void String::stringup()
{
    for (int i = 0; i < len; i++)
    {
        if (islower(str[i]))
            str[i] = toupper(str[i]);
    }
}

void String::stringlow()
{
    for (int i = 0; i < len; i++)
    {
        if (isupper(str[i]))
            str[i] = tolower(str[i]);
    }
}

int String::has(char ch) const
{
    int count = 0;
    for (int i = 0; i < len; i++)
    {
        if (str[i] == ch)
            count++;
    }
    return count;
}

// Two approaches
// 1.use loop to copy value from str1 and str2 one by one
// 2.use strcpy_s() and strcat_s() to copy at one go

// Approach 1
String operator+(const String&str1, const String& str2)
{
    int new_len = str1.len + str2.len;

    char*ps = new char[new_len + 1];
    for (int i = 0; i < str1.len; i++)
        ps[i] = str1[i];

    for (int i = str1.len; i < new_len + 1; i++)
        ps[i] = str2[i - str1.len];

    String temp(ps);
    delete[]ps;
    return temp;
}

/*
// Approach 2
String operator+(const String&str1, const String& str2)
{
	int new_len = str1.len + str2.len;
	char*ps = new char[new_len + 1];
	// end element '\0' copied
	strcpy_s(ps, new_len + 1, str1.str);
	// str1's end element '\0' covered and str2's '\0' copied
	strcat_s(ps, new_len + 1, str2.str);

	String temp(ps);
	delete[]ps;
	return temp;
}
*/

String operator+(const char* s, const String& str2)
{
    String temp(s);
    return temp + str2;
}

main

// pe12_2.cpp
#include <iostream>
using namespace std;
#include "string2.h"
int main()
{
    String s1(" and I am a C++ student.");
    String s2 = "Please enter your name: ";
    String s3;
    cout << s2; // overloaded << operator
    cin >> s3; // overloaded >> operator
    s2 = "My name is " + s3; // overloaded =, + operators
    cout << s2 << ".\n";
    s2 = s2 + s1;
    s2.stringup(); // converts string to uppercase
    cout << "The string\n" << s2 << "\ncontains " << s2.has('A')
         << " 'A' characters in it.\n";
    s1 = "red"; // String(const char *),
    // then String & operator=(const String&)
    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(); // converts string to lowercase
        for (int i = 0; i < 3; i++)
        {
            if (ans == rgb[i]) // overloaded == operator
            {
                cout << "That's right!\n";
                success = true;
                break;
            }
        }
        if (success)
            break;
        else
            cout << "Try again!\n";
    }
    cout << "Bye\n";
    cin.get();
    return 0;
}

C++ Premier Plus 6th edition - Programming excercise - Chapter12 -2

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