Challenge 3 – Can you draw the linear function correctly? in C++, using graphics.h BGI library

Difficulty x10

x5

This Challenge was proposed for the now defunct C/C++ programming list CWORLD in 1999.
The source code of the challenge has been updated to modern C++, but maintaining the essence of the challenge, which its original author wanted to transmit.

This code draws the linear function in an incorrect position, the objective of the challenge is to find and correct the error, so that the linear function is drawn in the correct position.

The WinBGIDLL library (graphics.h and conio.h) must be used to run the challenge code.

The final result of the program should look like the initial image of this post.

Source Code

#include "graphics.h"
#include "conio.h"
#include <string>
#include <iomanip>
#include <sstream>

#define MAXX		getmaxx()
#define MAXY		getmaxy()
#define CX		(MAXX / 2) /* This combination of macros defines the center of */
#define CY		(MAXY / 2) /* the coordinates on the screen */
#define DESDEX	-10 /* Defines from which x value the graphing will begin */
#define HASTAX	10 /* Needs explanation? */
#define ZOOM	4 /* The larger it is, the greater the range of coordinates that is shown on the screen */
#define CADA	(MAXX / 10) /* For the number of values ​​that will be shown on the axes */
/* In reality, the true zoom is the combination between ZOOM, and CADA */

#define F(X) (X*2/3)+4 /* This is the function that will be graphed */
#define DEFINICION 0.001

void axis();
void draw_func();


void main()
{	
	initwindow(1024, 768, "The world of chaos in C++ - Unlimited Programming");
	axis();
	draw_func();
	getchar();
	closegraph();
}


void axis() /* This procedure draws the axes according to the values ​​of the macros */
{
	int i;
	double j;
	std::string res;

	setcolor(WHITE);
	line(0, CY, MAXX, CY);	/* Draw the X axis */
	line(CX, 0, CX, MAXY);  /* Draw the Y axis */


	settextstyle(DEFAULT_FONT, VERT_DIR, 1);
	for (i = CX - CADA, j = 0; i >= 0; i -= CADA)	/* Draw at -X */
	{
		line(i, CY - 3, i, CY + 3);
		j -= ZOOM;

		std::stringstream stream;
		stream << std::fixed << std::setprecision(2) << j;
		res = stream.str();

		setcolor(CYAN);
		outtextxy(i, CY + 5, res.c_str());
		setcolor(WHITE);
	}

	for (i = CX + CADA, j = 0; i <= MAXX; i += CADA)	/* Draw at +X */
	{
		line(i, CY - 3, i, CY + 3);
		j += ZOOM;

		std::stringstream stream;
		stream << std::fixed << std::setprecision(2) << j;
		res = stream.str();

		setcolor(CYAN);
		outtextxy(i, CY + 5, res.c_str());
		setcolor(WHITE);
	}
	settextstyle(DEFAULT_FONT, HORIZ_DIR, 1);
	for (i = CY - CADA, j = 0; i >= 0; i -= CADA)	/* Draw at +Y */
	{
		line(CX - 3, i, CX + 3, i);
		j += ZOOM;

		std::stringstream stream;
		stream << std::fixed << std::setprecision(2) << j;
		res = stream.str();

		setcolor(CYAN);
		outtextxy(CX + 5, i, res.c_str());
		setcolor(WHITE);
	}

	for (i = CY + CADA, j = 0; i <= MAXY; i += CADA)	/* Draw at -Y */
	{
		line(CX - 3, i, CX + 3, i);
		j -= ZOOM;

		std::stringstream stream;
		stream << std::fixed << std::setprecision(2) << j;
		res = stream.str();

		setcolor(CYAN);
		outtextxy(CX + 5, i, res.c_str());
		setcolor(WHITE);
	}
	setcolor(GREEN);
	outtextxy(0, CY - 16, "-X");
	outtextxy(MAXX - 20, CY - 16, "+X");
	outtextxy(CX - 20, 0, "+Y");
	outtextxy(CX - 20, MAXY - 20, "-Y");
}

void draw_func() /* This procedure draws the function on the screen */
{
	double y, x, proporcion = CADA / ZOOM;
	for (x = DESDEX; x <= HASTAX; x += DEFINICION)
	{
		y = F(x);
		putpixel(x*proporcion, y*proporcion, YELLOW);
	}
}

AND FINALLY I CAN ONLY SAY …. BEST OF LUCK AND MAY THE BEST CODE WIN….

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Solution