Increment Decrement.

Increment Decrement.

Writing “a++” is equivalent to “a = a + 1”. Writing “a–” is equivalent to “a = a - 1”.

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int a;
int b;
boolean direction;

void setup() {
  size(640, 360);
  colorMode(RGB, width);
  a = 0;
  b = width;
  direction = true;
  frameRate(30);
}

void draw() {
  a++;
  if(a > width) {
    a = 0;
    direction = !direction;
  }
  if(direction == true){
    stroke(a);
  } else {
    stroke(width-a);
  }
  line(a, 0, a, height/2);

  b--;
  if(b < 0) {
    b = width;
  }
  if(direction == true) {
    stroke(width-b);
  } else {
    stroke(b);
  }
  line(b, height/2+1, b, height);
}

Functions Used

stroke()

Sets the color used to draw lines and borders around shapes

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size()

Defines the dimension of the display window width and height in units of pixels

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if

Allows the program to make a decision about which code to execute

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setup()

The setup() function is run once, when the program starts

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frameRate

The system variable frameRate contains the approximate frame rate of a running sketch

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colorMode()

Changes the way Processing interprets color data

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draw()

Called directly after setup(), the draw() function continuously executes the lines of code contained inside its block until the program is stopped or noLoop() is called

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line()

Draws a line (a direct path between two points) to the screen

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