Particles Revision

#include <cstdlib>
#include <cmath>
#include <cstring>
#include <iostream>
#include <Grapic.h>
#define CHMAX 255
#define MAXPART 255
#define MAXSPR 255

using namespace std;
using namespace grapic;

const char title[CHMAX] = "Particule";
const int WINX = 250;
const int WINY = 250;
const int DIMW = 500;
const int DT = 0.001;
const float G = 9.81;

struct Vec2
#pragma region Vector
{
    float x, y;
};

Vec2 make_complex(float x, float y)
{
    Vec2 c;
    c.x = x;
    c.y = y;
    return c;
}

Vec2 make_complex_exp(float r, float theta)
{
    Vec2 c;
    c.x = r * cos(theta);
    c.y = r * sin(theta);
    return c;
}

Vec2 operator+(Vec2 a, Vec2 b)
{
    Vec2 r;
    r.x = a.x + b.x;
    r.y = a.y + b.y;
    return r;
}

Vec2 operator+(float x, Vec2 a)
{
    Vec2 r;
    r.x = a.x + x;
    r.y = a.y + x;
    return r;
}

Vec2 operator-(Vec2 a, Vec2 b)
{
    Vec2 r;
    r.x = a.x - b.x;
    r.y = a.y - b.y;
    return r;
}

Vec2 operator*(float landa, Vec2 b)
{
    Vec2 r;
    r.x = landa * b.x;
    r.y = landa * b.y;
    return r;
}

Vec2 operator*(Vec2 a, Vec2 b)
{
    Vec2 r;
    r.x = a.x * b.x - a.y * b.y;
    r.y = a.x * b.y + b.x * a.y;
    return r;
}

Vec2 operator/(Vec2 a, float landa)
{
    Vec2 r;
    r.x = a.x / landa;
    r.y = a.y / landa;
    return r;
}
#pragma endregion


struct Particle
{
    Vec2 d, v, F;
    float m;
};

struct World
{
    int nbPart;
    Particle tab[MAXPART];
};

void init_part(Particle& p)
{
    p.m = 1;
    p.d = make_complex(DIMW / 2, DIMW / 2);
    p.v = make_complex(0, 0);
    p.F = make_complex(0, G * p.m);
}


void update_part(Particle& p)
{
    p.v = p.v + (1 / p.m) * DT * p.F;
    p.d = p.d + DT * p.v;
    if (p.d.y < 0)
    {
        p.d.y = -p.d.y;
        p.v.y = -p.v.y;
        p.v = 0.8 * p.v;
        p.F.y = -p.F.y;
    }
    if (p.d.y > DIMW)
    {
        p.d.y = DIMW - (p.d.y - DIMW);
        p.v.y = -p.v.y;
        p.v = 0.8 * p.v;
        p.F.y = -p.F.y;
    }
    if (p.d.x < 0)
    {
        p.d.x = -p.d.x;
        p.v.x = -p.v.x;
        p.v = 0.8 * p.v;
        p.F.x = -p.F.x;
    }
    if (p.d.x > DIMW)
    {
        p.d.x = DIMW - (p.d.x - DIMW);
        p.v.x = -p.v.x;
        p.v = 0.8 * p.v;
        p.F.x = -p.F.x;
    }
    if (p.F.y < 0)
        p.d.y -= p.F.y / (p.F.y * 10);
    else if (p.F.y > 0)
        p.d.y += p.F.y / (p.F.y * 10);
    else if (p.F.x < 0)
        p.d.x -= p.F.x / (p.F.x * 10);
    else if (p.F.x > 0)
        p.d.x += p.F.x / (p.F.x * 10);
}


void init(World& w)
{
    backgroundColor(0);
    w.nbPart = 0;
}


void update(World& w)
{
}

void draw(World& w)
{
}

int main(void)
{
    bool stop = false;
    winInit(title, WINX, WINY);
    srand(time(NULL));
    World w;
    init(w);
    while (!stop)
    {
        winClear();
        draw(w);
        update(w);
        stop = winDisplay();
    }
    winQuit();
    return 0;
}