Confusing Java syntax...
- by posfan12
I'm trying to convert the following code (from Wikipedia) from Java to JavaScript:
/*
* 3 June 2003, [[:en:User:Cyp]]:
* Maze, generated by my algorithm
* 24 October 2006, [[:en:User:quin]]:
* Source edited for clarity
* 25 January 2009, [[:en:User:DebateG]]:
* Source edited again for clarity and reusability
* 1 June 2009, [[:en:User:Nandhp]]:
* Source edited to produce SVG file when run from the command-line
*
* This program was originally written by [[:en:User:Cyp]], who
* attached it to the image description page for an image generated by
* it on en.wikipedia. The image was licensed under CC-BY-SA-3.0/GFDL.
*/
import java.awt.*;
import java.applet.*;
import java.util.Random;
/* Define the bit masks */
class Constants {
public static final int WALL_ABOVE = 1;
public static final int WALL_BELOW = 2;
public static final int WALL_LEFT = 4;
public static final int WALL_RIGHT = 8;
public static final int QUEUED = 16;
public static final int IN_MAZE = 32;
}
public class Maze extends java.applet.Applet {
/* The width and height (in cells) of the maze */
private int width;
private int height;
private int maze[][];
private static final Random rnd = new Random();
/* The width in pixels of each cell */
private int cell_width;
/* Construct a Maze with the default width, height, and cell_width */
public Maze() {
this(20,20,10);
}
/* Construct a Maze with specified width, height, and cell_width */
public Maze(int width, int height, int cell_width) {
this.width = width;
this.height = height;
this.cell_width = cell_width;
}
/* Initialization method that will be called when the program is
* run from the command-line. Maze will be written as SVG file. */
public static void main(String[] args) {
Maze m = new Maze();
m.createMaze();
m.printSVG();
}
/* Initialization method that will be called when the program is
* run as an applet. Maze will be displayed on-screen. */
public void init() {
createMaze();
}
/* The maze generation algorithm. */
private void createMaze(){
int x, y, n, d;
int dx[] = { 0, 0, -1, 1 };
int dy[] = { -1, 1, 0, 0 };
int todo[] = new int[height * width], todonum = 0;
/* We want to create a maze on a grid. */
maze = new int[width][height];
/* We start with a grid full of walls. */
for (x = 0; x < width; ++x) {
for (y = 0; y < height; ++y) {
if (x == 0 || x == width - 1 || y == 0 || y == height - 1) {
maze[x][y] = Constants.IN_MAZE;
} else {
maze[x][y] = 63;
}
}
}
/* Select any square of the grid, to start with. */
x = 1 + rnd.nextInt (width - 2);
y = 1 + rnd.nextInt (height - 2);
/* Mark this square as connected to the maze. */
maze[x][y] &= ~48;
/* Remember the surrounding squares, as we will */
for (d = 0; d < 4; ++d) {
if ((maze[][d][][d] & Constants.QUEUED) != 0) {
/* want to connect them to the maze. */
todo[todonum++] = ((x + dx[d]) << Constants.QUEUED) | (y + dy[d]);
maze[][d][][d] &= ~Constants.QUEUED;
}
}
/* We won't be finished until all is connected. */
while (todonum > 0) {
/* We select one of the squares next to the maze. */
n = rnd.nextInt (todonum);
x = todo[n] >> 16; /* the top 2 bytes of the data */
y = todo[n] & 65535; /* the bottom 2 bytes of the data */
/* We will connect it, so remove it from the queue. */
todo[n] = todo[--todonum];
/* Select a direction, which leads to the maze. */
do {
d = rnd.nextInt (4);
}
while ((maze[][d][][d] & Constants.IN_MAZE) != 0);
/* Connect this square to the maze. */
maze[x][y] &= ~((1 << d) | Constants.IN_MAZE);
maze[][d][][d] &= ~(1 << (d ^ 1));
/* Remember the surrounding squares, which aren't */
for (d = 0; d < 4; ++d) {
if ((maze[][d][][d] & Constants.QUEUED) != 0) {
/* connected to the maze, and aren't yet queued to be. */
todo[todonum++] = ((x + dx[d]) << Constants.QUEUED) | (y + dy[d]);
maze[][d][][d] &= ~Constants.QUEUED;
}
}
/* Repeat until finished. */
}
/* Add an entrance and exit. */
maze[1][1] &= ~Constants.WALL_ABOVE;
maze[width - 2][height - 2] &= ~Constants.WALL_BELOW;
}
/* Called by the applet infrastructure to display the maze on-screen. */
public void paint(Graphics g) {
drawMaze(g);
}
/* Called to write the maze to an SVG file. */
public void printSVG() {
System.out.format("<svg width=\"%d\" height=\"%d\" version=\"1.1\""
+ " xmlns=\"http://www.w3.org/2000/svg\">\n",
width*cell_width, height*cell_width);
System.out.println(" <g stroke=\"black\" stroke-width=\"1\""
+ " stroke-linecap=\"round\">");
drawMaze(null);
System.out.println(" </g>\n</svg>");
}
/* Main maze-drawing loop. */
public void drawMaze(Graphics g) {
int x, y;
for (x = 1; x < width - 1; ++x) {
for (y = 1; y < height - 1; ++y) {
if ((maze[x][y] & Constants.WALL_ABOVE) != 0)
drawLine( x * cell_width, y * cell_width,
(x + 1) * cell_width, y * cell_width, g);
if ((maze[x][y] & Constants.WALL_BELOW) != 0)
drawLine( x * cell_width, (y + 1) * cell_width,
(x + 1) * cell_width, (y + 1) * cell_width, g);
if ((maze[x][y] & Constants.WALL_LEFT) != 0)
drawLine( x * cell_width, y * cell_width,
x * cell_width, (y + 1) * cell_width, g);
if ((maze[x][y] & Constants.WALL_RIGHT) != 0)
drawLine((x + 1) * cell_width, y * cell_width,
(x + 1) * cell_width, (y + 1) * cell_width, g);
}
}
}
/* Draw a line, either in the SVG file or on the screen. */
public void drawLine(int x1, int y1, int x2, int y2, Graphics g) {
if ( g != null ) g.drawLine(x1, y1, x2, y2);
else System.out.format(" <line x1=\"%d\" y1=\"%d\""
+ " x2=\"%d\" y2=\"%d\" />\n", x1, y1, x2, y2);
}
}
Anyway, I was chugging along fairly quickly when I came to a bit that I just don't understand:
/* Remember the surrounding squares, as we will */
for (var d = 0; d < 4; ++d) {
if ((maze[][d][][d] & Constants.QUEUED) != 0) {
/* want to connect them to the maze. */
todo[todonum++] = ((x + dx[d]) << Constants.QUEUED) | (y + dy[d]);
maze[][d][][d] &= ~Constants.QUEUED;
}
}
What I don't get is why there are four sets of brackets following the "maze" parameter instead of just two, since "maze" is a two dimensional array, not a four dimensional array.
I'm sure there's a good reason for this. Problem is, I just don't get it.
Thanks!
