c_cpp hello_world.cpp

Posted 2021-05-14

#include<iostream>

#define PI 3.14159
#define NEWLINE '\n'

int main()
{
    double r = 5; // radius
    double circle;

    circle = 2 * PI * r;
    std::cout << circle;
    std::cout << NEWLINE;
}

#include<iostream>

const double pi = 3.14159;
const char newline = '\n';

int main()
{
    double r = 5;
    double circle;

    circle = 2 * pi * r;
    std::cout << circle;
    std::cout << newline;
}

#include <iostream>
#include <string>

int main()
{
    // std::string mystring;
    // mystring = "This is a sting";
    std::string mystring ("This is a string");
    std::cout << mystring;
    return 0;
}

// initialization of variables

#include <iostream>
using namespace std;

int main ()
{
    int a=5;               // initial value: 5
    int b(3);              // initial value: 3
    int c(2);              // initial value: 2
    int result;            // initial value undetermined

    a = a + b;
    result = a - c;
    cout << result;

    return 0;
}

// operating with variables

#include <iostream>
using namespace std;

int main ()
{
    // declaring variables:
    int a, b;
    int result;

    // process:
    a = 5;
    b = 2;
    a = a + 1;
    result = a - b;

    // print out the result:
    cout << result;

    // terminate the program:
    return 0;
}

#include <vector>
#include <iostream>

int main()
{
    std::vector<int> array;

    for (int i=0; i<10; i++) {
        array.push_back(i);
    }

    for (int i=0; i<10; i++) {
        std::cout << array[i] << std::endl;
    }

    return 0;
}

#include <stdio.h>

//関数vAdd , vSetもクラスに含めます。アクセスは当然publicで
class C3DVec{
    private:

    public:
        float x , y , z;

        C3DVec operator+(C3DVec v2)
        {
            C3DVec vRet;
            //v1は自分の値を使えばよいので、引数はv2だけでよくなる。

            vRet.x = x + v2.x;
            vRet.y = y + v2.y;
            vRet.z = z + v2.z;

            return vRet;
        }
        void vSet(double ix , double iy , double iz)
        {
            //メンバ変数の名前とダブらないように引数をix,iy,izとする。
            //自分のメンバ変数の値をセットすればよいので戻り値は必要ない
            x = ix;
            y = iy;
            z = iz;
        }
};

int main()
{
    C3DVec vA , vB , vC;

    vA.vSet(2 , 1 , -2);
    vB.vSet(1 , 1 , 1 );


    // vC = vA.operator+(vB);
    vC = vA + vB;

    printf("C = %f %f %f\n" , vC.x , vC.y , vC.z);

    return 0;
}

#include <stdio.h>

class C3DVec {
    private:

    public:
        float x, y, z;
};

int main()
{
    C3DVec vA, vB, vC;

    vA.x = 2;
    vA.y = 1;
    vA.z = -2;

    vB.x = 1;
    vB.y = 1;
    vB.z = 1;

    vC.z = vA.x + vB.x;
    vC.y = vA.y + vB.y;
    vC.z = vA.z + vB.z;

    printf("C = %f %f %f\n" , vC.x , vC.y , vC.z);

    return 0;
}

#include <stdio.h>
int main()
{
    float ax,ay,az , bx,by,bz , cx,cy,cz;

    ax = 2;
    ay = 1;
    az = -2;

    bx = 1;
    by = 1;
    bz = 1;

    cx = ax + bx;
    cy = ay + by;
    cz = az + bz;

    printf("C = %f %f %f\n" , cx , cy , cz);

    return 0;
}

#include <iostream>

int main()
{
    std::cout << "Hello, World! ";
    std::cout << "I'm a C++ program";
}

#include <iostream>

int main()
{
    std::cout << "Hello, World!";
}