в 14:21, 25 мая 2010

2010-05-25T14:21:06Z

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2010-05-25T10:28:22Z

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==additional meanings for the + and = operations==

<source lang="cpp">
#include <iostream>
#include <string.h>
using namespace std;
class str_type {
char string[80];
public:
str_type(char *str = "\0") { strcpy(string, str); }

str_type operator+(str_type str);
str_type operator+(char *str);

str_type operator=(str_type str);
str_type operator=(char *str);

void show_str(void) { cout << string; }
} ;

str_type str_type::operator+(str_type str) {
str_type temp;

strcpy(temp.string, string);
strcat(temp.string, str.string);
return temp;
}

str_type str_type::operator=(str_type str) {
strcpy(string, str.string);
return *this;
}

str_type str_type::operator=(char *str)
{
str_type temp;

strcpy(string, str);
strcpy(temp.string, string);
return temp;
}

str_type str_type::operator+(char *str)
{
str_type temp;

strcpy(temp.string, string);
strcat(temp.string, str);
return temp;
}

main(void)
{
str_type a("Hello "), b("There"), c;

c = a + b;

c.show_str();
cout << "\n";

a = "to program in because";
a.show_str();
cout << "\n";

b = c = "C++ is fun";

c = c+" "+a+" "+b;
c.show_str();

return 0;
}

</source>

==Define operator +(plus) and cast to double operator==

<source lang="cpp">
#include <iostream>
using namespace std;
class Power {
double b;
int e;
double val;
public:
Power(double base, int exp);
Power operator+(Power obj) {
double base;
int exp;
base = b + obj.b;
exp = e + obj.e;
Power temp(base, exp);
return temp;
}
operator double(void) {return val;}
};
Power::Power(double base, int exp){
b = base;
e = exp;
val = 1;
if (exp!=0)
while(exp-- > 0)
val *= b;
}
int main(void){
Power pwr1(4.0, 2);
double doub1;
doub1 = pwr1;
cout << (doub1 + 100.2) << endl;
Power pwr2(3.3, 3), pwr3(0,0);
pwr3 = pwr1 + pwr2;
doub1 = pwr3;
cout << doub1;
}

</source>

==Friendly operator+==

<source lang="cpp">
#include <iostream>
#include <string.h>
using namespace std;
class String{
public:
String();
String(const char *const);
String(const String &);
~String();
char & operator[](int offset);
char operator[](int offset) const;
String operator+(const String&);
friend String operator+(const String&, const String&);
void operator+=(const String&);
String & operator= (const String &);
int GetLen()const { return itsLen; }
const char * GetString() const { return itsString; }
private:
String (int);
char * itsString;
unsigned short itsLen;
};
String::String()
{
itsString = new char[1];
itsString[0] = "\0";
itsLen=0;
}
String::String(int len)
{
itsString = new char[len+1];
for (int i = 0; i<=len; i++)
itsString[i] = "\0";
itsLen=len;
}
String::String(const char * const cString)
{
itsLen = strlen(cString);
itsString = new char[itsLen+1];
for (int i = 0; i<itsLen; i++)
itsString[i] = cString[i];
itsString[itsLen]="\0";
}
String::String (const String & rhs)
{
itsLen=rhs.GetLen();
itsString = new char[itsLen+1];
for (int i = 0; i<itsLen;i++)
itsString[i] = rhs[i];
itsString[itsLen] = "\0";
}
String::~String ()
{
delete [] itsString;
itsLen = 0;
}
String& String::operator=(const String & rhs)
{
if (this == &rhs)
return *this;
delete [] itsString;
itsLen=rhs.GetLen();
itsString = new char[itsLen+1];
for (int i = 0; i<itsLen;i++)
itsString[i] = rhs[i];
itsString[itsLen] = "\0";
return *this;
}
char & String::operator[](int offset)
{
if (offset > itsLen)
return itsString[itsLen-1];
else
return itsString[offset];
}
char String::operator[](int offset) const
{
if (offset > itsLen)
return itsString[itsLen-1];
else
return itsString[offset];
}
String String::operator+(const String& rhs)
{
int totalLen = itsLen + rhs.GetLen();
String temp(totalLen);
int i, j;
for (i = 0; i<itsLen; i++)
temp[i] = itsString[i];
for (j = 0, i = itsLen; j<rhs.GetLen(); j++, i++)
temp[i] = rhs[j];
temp[totalLen]="\0";
return temp;
}
String operator+(const String& lhs, const String& rhs)
{
int totalLen = lhs.GetLen() + rhs.GetLen();
String temp(totalLen);
int i, j;
for (i = 0; i<lhs.GetLen(); i++)
temp[i] = lhs[i];
for (j = 0, i = lhs.GetLen(); j<rhs.GetLen(); j++, i++)
temp[i] = rhs[j];
temp[totalLen]="\0";
return temp;
}
int main()
{
String s1("String One ");
String s2("String Two ");
char *c1 = { "C-String One " } ;
String s3;
String s4;
String s5;
cout << "s1: " << s1.GetString() << endl;
cout << "s2: " << s2.GetString() << endl;
cout << "c1: " << c1 << endl;
s3 = s1 + s2;
cout << "s3: " << s3.GetString() << endl;
s4 = s1 + c1;
cout << "s4: " << s4.GetString() << endl;
s5 = c1 + s2;
cout << "s5: " << s5.GetString() << endl;
return 0;
}

</source>

==friend overloaded + operator==

<source lang="cpp">
#include <iostream>
using namespace std;
class Distance{
private:
int feet;
float inches;
public:
Distance(){
feet = 0;
inches = 0.0;
}
Distance( float fltfeet ){
feet = int(fltfeet);
inches = 12*(fltfeet-feet);
}
Distance(int ft, float in){
feet = ft;
inches = in;
}
void showdist(){
cout << feet << "\"-" << inches << "\"";
}
friend Distance operator + (Distance, Distance);
};
Distance operator + (Distance d1, Distance d2){
int f = d1.feet + d2.feet;
float i = d1.inches + d2.inches;
if(i >= 12.0){
i -= 12.0; f++;
}
return Distance(f,i);
}
int main(){
Distance d1 = 2.5;
Distance d2 = 1.25;
Distance d3;
cout << "\nd1 = ";
d1.showdist();
cout << "\nd2 = ";
d2.showdist();

d3 = d1 + 10.0;
cout << "\nd3 = "; d3.showdist();
d3 = 10.0 + d1;
cout << "\nd3 = "; d3.showdist();
cout << endl;
return 0;
}

</source>

==+ is overloaded for three_d + three_d and for three_d + int.==

<source lang="cpp">
#include <iostream>
using namespace std;
class three_d {
int x, y, z;
public:
three_d() { x = y = z = 0; }
three_d(int i, int j, int k) { x = i; y = j; z = k; }
// Add two three_d objects together.
three_d operator+(three_d rh_op);
// Add an integer to a three_d object.
three_d operator+(int rh_op);
// Subtract two three_d objects.
three_d operator-(three_d rh_op);
// Overload assignment.
three_d operator=(three_d rh_op);
// Overload ==.
bool operator==(three_d rh_op);
// Overload - for unary operation.
three_d operator-();
// Let the overloaded inserter be a friend.
friend ostream &operator<<(ostream &strm, three_d op);
// Let the overloaded + be a friend.
friend three_d operator+(int lh_op, three_d rh_op);
};
// Overload binary + so that corresponding coordinates are added.
three_d three_d::operator+(three_d rh_op)
{
three_d temp;
temp.x = x + rh_op.x;
temp.y = y + rh_op.y;
temp.z = z + rh_op.z;
return temp;
}
// Overload binary + so that an integer can be added to a three_d object.
three_d three_d::operator+(int rh_op)
{
three_d temp;
temp.x = x + rh_op;
temp.y = y + rh_op;
temp.z = z + rh_op;
return temp;
}
// Overload binary - so that corresponding coordinates are subtracted.
three_d three_d::operator-(three_d rh_op)
{
three_d temp;
temp.x = x - rh_op.x;
temp.y = y - rh_op.y;
temp.z = z - rh_op.z;
return temp;
}
// Overload unary - so that it negates the coordinates.
three_d three_d::operator-()
{
three_d temp;
temp.x = -x;
temp.y = -y;
temp.z = -z;
return temp;
}
// Overload assignment for three_d.
three_d three_d::operator=(three_d rh_op)
{
x = rh_op.x;
y = rh_op.y;
z = rh_op.z;
return *this;
}
// Overload == for a three_d object.
bool three_d::operator==(three_d rh_op)
{
if( (x == rh_op.x) && (y == rh_op.y) && (z == rh_op.z) )
return true;
return false;
}
// These are non-member operator functions.
//
// Overload << as a custom inserter for three_d objects.
ostream &operator<<(ostream &strm, three_d op) {
strm << op.x << ", " << op.y << ", " << op.z << endl;
return strm;
}
// Overload + for int + obj.
three_d operator+(int lh_op, three_d rh_op) {
three_d temp;
temp.x = lh_op + rh_op.x;
temp.y = lh_op + rh_op.y;
temp.z = lh_op + rh_op.z;
return temp;
}
int main()
{
three_d objA(1, 2, 3), objB(10, 10, 10), objC;
cout << "This is objA: " << objA;
cout << "This is objB: " << objB;
// Obtain the negation of objA.
objC = -objA;
cout << "This is -objA: " << objC;
// Add objA and objB together.
objC = objA + objB;
cout << "objA + objB: " << objC;
// Subtract objB from objA.
objC = objA - objB;
cout << "objA - objB: " << objC;
// Add obj + int.
objC = objA + 10;
cout << "objA + 10: " << objC;
// Add int + obj.
objC = 100 + objA;
cout << "100 + objA: " << objC;
// Compare two objects.
if(objA == objB) cout << "objA is equal to objB.\n";
else cout << "objA is not equal to objB.\n";
return 0;
}

</source>

==overloaded "+" operator adds two Distances==

<source lang="cpp">
#include <iostream>
using namespace std;
class Distance
{
private:
int feet;
float inches;
public:
Distance() : feet(0), inches(0.0){ }
Distance(int ft, float in) : feet(ft), inches(in) { }
void getdist(){
cout << "\nEnter feet: "; cin >> feet;
cout << "Enter inches: "; cin >> inches;
}
void showdist() const { cout << feet << "\"-" << inches << "\""; }
Distance operator + ( Distance ) const;
};
Distance Distance::operator + (Distance d2) const{
int f = feet + d2.feet;
float i = inches + d2.inches;
if(i >= 12.0){
i -= 12.0;
f++;
}
return Distance(f,i);
}
int main() {
Distance dist1, dist3, dist4;
dist1.getdist();
Distance dist2(11, 6.25);
dist3 = dist1 + dist2;
dist4 = dist1 + dist2 + dist3;
cout << "dist1 = "; dist1.showdist(); cout << endl;
cout << "dist2 = "; dist2.showdist(); cout << endl;
cout << "dist3 = "; dist3.showdist(); cout << endl;
cout << "dist4 = "; dist4.showdist(); cout << endl;
return 0;
}

</source>

==overloaded "+" operator concatenates strings==

<source lang="cpp">
#include <iostream>
using namespace std;
#include <string.h>
#include <stdlib.h>
class String{
private:
enum { SZ=80 };
char str[SZ];
public:
String() { strcpy(str, ""); }
String( char s[] ) { strcpy(str, s); }
void display() const { cout << str; }
String operator + (String ss) const {
String temp;
if( strlen(str) + strlen(ss.str) < SZ ){
strcpy(temp.str, str);
strcat(temp.str, ss.str);
}else{
cout << "\nString overflow"; exit(1);
}
return temp;
}
};
int main(){
String s1 = "aaa ";
String s2 = "bbb";
String s3;
s1.display();
s2.display();
s3.display();
s3 = s1 + s2;
s3.display();
return 0;
}

</source>

==Overload + for "ob + int" as well as "ob + ob".==

<source lang="cpp">
#include <iostream>
using namespace std;
class MyClass {
int x, y;
public:
MyClass() {
x=0;
y=0;
}
MyClass(int i, int j) {
x=i;
y=j;
}
void getXY(int &i, int &j) {
i=x;
j=y;
}
MyClass operator+(MyClass object2); // ob + ob
MyClass operator+(int i); // ob + int
};
// Overload + relative to MyClass class.
MyClass MyClass::operator+(MyClass object2)
{
MyClass temp;
temp.x = x + object2.x;
temp.y = y + object2.y;
return temp;
}
// Overload + for ob + int
MyClass MyClass::operator+(int i)
{
MyClass temp;
temp.x = x + i;
temp.y = y + i;
return temp;
}
int main()
{
MyClass object1(10, 10), object2(5, 3), object3;
int x, y;
object3 = object1 + object2; // add two objects - this calls operator+(MyClass)
object3.getXY(x, y);
cout << "(object1+object2) X: " << x << ", Y: " << y << endl;
object3 = object1 + 100; // add object + int - this call operator+(int)
object3.getXY(x, y);
cout << "(object1+100) X: " << x << ", Y: " << y << endl;
return 0;
}

</source>

==Overloading the + (or any other binary operator) using a friend allows a built-in type to occur on the left or right side of the operator.==

<source lang="cpp">
#include <iostream>
using namespace std;
class MyClass {
public:
int count;
MyClass operator=(int i);
friend MyClass operator+(MyClass ob, int i);
friend MyClass operator+(int i, MyClass ob);
};

MyClass MyClass::operator=(int i)
{
count = i;
return *this;
}

// This handles ob + int.
MyClass operator+(MyClass ob, int i)
{
MyClass temp;

temp.count = ob.count + i;
return temp;
}

// This handles int + ob.
MyClass operator+(int i, MyClass ob)
{
MyClass temp;

temp.count = ob.count + i;
return temp;
}

main(void)
{
MyClass obj;
obj = 10;
cout << obj.count << " ";

obj = 10 + obj;
cout << obj.count << " ";

obj = obj + 12;
cout << obj.count;

return 0;
}

</source>

==overload the "+" operator so that several angles, in the format degrees minutes seconds, can be added directly.==

<source lang="cpp">
#include <iostream>
#include <stdlib.h>
#include <string.h>
using namespace std;
int totaldegrees, totalminutes, totalseconds;
class angle_value {
int degrees, minutes, seconds;

public:
angle_value() {degrees=0,minutes=0, seconds=0;} // constructor
angle_value(char *);
angle_value operator +(angle_value);
};
angle_value::angle_value(char *angle_sum)
{
degrees=atoi(strtok(angle_sum,"d"));
minutes=atoi(strtok(0,"m"));
seconds=atoi(strtok(0,"s"));
}

angle_value angle_value::operator+(angle_value angle_sum){
angle_value ang;
ang.seconds=(seconds+angle_sum.seconds)%60;
ang.minutes=((seconds+angle_sum.seconds)/60+ minutes+angle_sum.minutes)%60;
ang.degrees=((seconds+angle_sum.seconds)/60+ minutes+angle_sum.minutes)/60;
ang.degrees+=degrees+angle_sum.degrees;
totaldegrees=ang.degrees;
totalminutes=ang.minutes;
totalseconds=ang.seconds;
return ang;
}
main()
{
char str1[] = "37d 15m 56s";
angle_value angle1(str1);

char str2[] = "10d 44m 44s";
angle_value angle2(str2);

char str3[] = "75d 17m 59s";
angle_value angle3(str3);

char str4[] = "130d 32m 54s";
angle_value angle4(str4);

angle_value sum_of_angles;
sum_of_angles=angle1+angle2+angle3+angle4;
cout << "The sum of the angles is " << totaldegrees << "d "
<< totalminutes << "m " << totalseconds << "s" << endl;
return (0);
}

</source>

==Overload the + relative to MyClass.==

<source lang="cpp">
#include <iostream>
using namespace std;
class MyClass {
int x, y;
public:
MyClass() {
x=0;
y=0;
}
MyClass(int i, int j) {
x=i;
y=j;
}
void getXY(int &i, int &j) {
i=x;
j=y;
}
MyClass operator+(MyClass object2);
};
// Overload +
MyClass MyClass::operator+(MyClass object2)
{
MyClass temp;
temp.x = x + object2.x;
temp.y = y + object2.y;
return temp;
}
int main()
{
MyClass object1(10, 10), object2(5, 3), object3;
int x, y;
object3 = object1 + object2; // add two objects - this calls operator+()
object3.getXY(x, y);
cout << "(object1+object2) X: " << x << ", Y: " << y << endl;
return 0;
}

</source>

==String class with custom +/- operator==

<source lang="cpp">
#include <iostream>
#include <iomanip>
#include <string.h>
using namespace std;
class String
{
public:
char *operator +(char *append_str)
{ return(strcat(buffer, append_str)); };

char *operator -(char letter);
String(char *string)
{ strcpy(buffer, string);
length = strlen(buffer);
}
void show_string() { cout << buffer; };
private:
char buffer[256];
int length;
};
int main(void){
String title("A");
title = title + "Programmer"s Bible\n";
title.show_string();
}

</source>

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