C++/Data Type/Double
Содержание
- 1 Calculates the area of a circle based on a radius inputted by the user.
- 2 Circumference and area of a circle with radius 2.5
- 3 Create a table of square roots and squares.
- 4 Define, input and output double
- 5 double value cout format
- 6 Do while loop with double value type
- 7 Get sin, cos and tan value of an angle in double
- 8 Get the square root, power and log value of a double
- 9 long double: Formatting includes precision, width, alignment, and format of large numbers.
- 10 long double: Formatting includes precision, width and fixed with default of right justification when printing.
- 11 Read double value from keyboard and save it to another value
- 12 Using atof: convert string to double
- 13 Using strtod: convert string to double
Calculates the area of a circle based on a radius inputted by the user.
#include <iostream>
#include <cmath>
using namespace std;
int main(void)
{
double radius, area;
cout << "Enter radius of circle: ";
cin >> radius;
area = 3.14159 * pow(radius, 2);
cout << "The area is " << area << endl;
return 0;
}
Circumference and area of a circle with radius 2.5
#include <iostream>
using namespace std;
const double pi = 3.141593;
int main()
{
double area, circuit, radius = 1.5;
area = pi * radius * radius;
circuit = 2 * pi * radius;
cout << "\nTo Evaluate a Circle\n" << endl;
cout << "Radius: " << radius << endl
<< "Circumference: " << circuit << endl
<< "Area: " << area << endl;
return 0;
}
Create a table of square roots and squares.
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
double x;
cout.precision(4);
cout << " x sqrt(x) x^2\n\n";
for(x = 2.0; x <= 20.0; x++) {
cout.width(7);
cout << x << " ";
cout.width(7);
cout << sqrt(x) << " ";
cout.width(7);
cout << x*x << "\n";
}
return 0;
}
Define, input and output double
#include <iostream>
using namespace std;
int main()
{
double hours, wage;
cout << "Enter hours worked: ";
cin >> hours;
cout << "Enter wage per hour: ";
cin >> wage;
cout << "Pay is: $" << wage * hours;
return 0;
}
double value cout format
#include <iostream>
using namespace std;
int main()
{
double x = 12.0;
cout.precision(2); // Precision 2
cout << " By default: " << x << endl;
cout << " showpoint: " << showpoint << x << endl;
cout << " fixed: " << fixed << x << endl;
cout << " scientific: " << scientific << x << endl;
return 0;
}
Do while loop with double value type
#include <iostream>
using namespace std;
int main()
{
double feet;
do {
cout << "Enter feet (0 to quit): ";
cin >> feet;
cout << feet * 12 << " inches\n";
} while (feet != 0.0);
return 0;
}
Get sin, cos and tan value of an angle in double
#include <iostream>
#include <cmath>
using namespace std;
int main(){
double angle, dsine,dcos,dtan;
cout << "Please enter an angle in radians \n";
cin >> angle;
dcos =cos(angle);
dsine =sin(angle);
dtan =tan(angle);
cout << " Your angles trigonometric functions are \n";
cout << " Sine is " << dsine << "\n";
cout << " Cosine is " << dcos << "\n";
cout << " Tangent is " << dtan << "\n";
return 0;
}
Get the square root, power and log value of a double
#include <iostream>
#include <cmath>
using namespace std;
int main()
{
double number, dsqrt,dpow,dlog;
cout << "Please enter a number \n";
cin >> number;
dsqrt =sqrt(number);
dpow =pow(number,5);
dlog =log(number);
cout << " Math Example\n";
cout << " Square Root is " << dsqrt << "\n";
cout << " Raised to the fifth power is " << dpow << "\n";
cout << " Log is " << dlog << "\n";
return 0;
}
long double: Formatting includes precision, width, alignment, and format of large numbers.
#include <iostream>
#include <iomanip>
using namespace std;
int main(){
long double number,factorial;
number=1.0;
factorial=1.0;
cout.precision(0); // no decimal point
cout.setf(ios::left); // left justify numbers
cout.setf(ios::fixed); // use fixed format
for(int i=0;i<25;i++) {
factorial*=number;
number=number+1.0;
cout.width(30); // width of 30 characters
cout << factorial << endl;
}
return (0);
}
long double: Formatting includes precision, width and fixed with default of right justification when printing.
#include <iostream>
#include <iomanip>
using namespace std;
main( )
{
long double number,factorial;
number=1.0;
factorial=1.0;
cout.precision(0); // no decimal place
cout.setf(ios::fixed); // use fixed format
for(int i=0;i<25;i++) {
factorial*=number;
number=number+1.0;
cout.width(30); // width of 30 characters
cout << factorial << endl;
}
return (0);
}
Read double value from keyboard and save it to another value
#include <iomanip>
#include <ios>
#include <iostream>
#include <string>
using std::cin; using std::setprecision;
using std::cout; using std::string;
using std::endl; using std::streamsize;
int main()
{
cout << "Please enter your first name: ";
string name;
cin >> name;
cout << "Hello, " << name << "!" << endl;
cout << "Please enter your midterm and final exam grades: ";
double midterm, final;
cin >> midterm >> final;
cout << "Enter all your homework grades, " "followed by end-of-file: ";
int count = 0;
double sum = 0;
double x;
while (cin >> x) {
++count;
sum += x;
}
streamsize prec = cout.precision();
cout << "Your final grade is " << setprecision(3)
<< 0.2 * midterm + 0.4 * final + 0.4 * sum / count
<< setprecision(prec) << endl;
return 0;
}
Using atof: convert string to double
#include <iostream>
#include <stdlib.h>
using namespace std;
int main()
{
double d = atof( "99.0" );
cout << "The string \"99.0\" converted to double is "
<< d << "\nThe converted value divided by 2 is "
<< d / 2.0 << endl;
return 0;
}
Using strtod: convert string to double
#include <iostream>
#include <stdlib.h>
using namespace std;
int main()
{
double d;
char *string = "51.2% are admitted", *stringPtr;
d = strtod( string, &stringPtr );
cout << "The string \"" << string
<< "\" is converted to the\ndouble value " << d
<< " and the string \"" << stringPtr << "\"" << endl;
return 0;
}