Step by Step solution about How to resolve the algorithm Animation step by step in the Haskell programming language

This Haskell code sets up a basic animation using the Graphics.HGL library. Here's a detailed breakdown:

1. Import Statements: The code starts by importing various modules from the Graphics.HGL library, including those for creating windows, drawing graphics, and handling fonts.

2. runAnim Function: This is the main function that sets up and runs the animation. It uses the runGraphics function to create a graphics loop.

3. Creating a Window: Inside the runGraphics block, the code calls openWindowEx to create a graphics window with the specified title, size, and double buffering.

4. Creating a Font: It creates a font using createFont with a size of (64,28) and other font attributes.

5. Animation Loop (loop Function): The core of the animation is in the loop function. It takes two arguments: t, which represents the text to be displayed, and dir, which determines the direction of the animation.

   • The function starts by checking if any window events have occurred using maybeGetWindowEvent. If a button is pressed and released, it changes the direction of the animation.

   • It then updates the text to be displayed. If dir is 1, the last character of t is moved to the beginning, and if it's -1, the first character is moved to the end.

   • The updated text is set as the graphic in the window using setGraphic, and the next animation tick is retrieved using getWindowTick.

   • Finally, the loop function calls itself recursively with the updated text and direction, continuing the animation until the window is closed.

6. Window Closing: The bracket function ensures that the window is properly closed when the program exits.

7. Running the Program: The runAnim function is called with the runGraphics function to start the animation. The user can interact with the animation by pressing buttons on the window.

The provided code is written in Haskell and uses the HGL library for graphics. It creates a basic animation, displaying the text "Hello world ! " on a window. The animation consists of a simple loop that moves the text from left to right and back again.

Importing necessary modules:

• Graphics.HGL.Units: Contains type aliases like Time, Point, and Size.
• Graphics.HGL.Draw.Monad: Provides the Graphic type and functions for drawing.
• Graphics.HGL.Draw.Text: Provides functions for drawing text to a graphic.
• Graphics.HGL.Draw.Font: Provides functions for creating and managing fonts.
• Graphics.HGL.Window: Contains types and functions for creating and managing windows.
• Graphics.HGL.Run: Contains functions for running the graphical application.
• Graphics.HGL.Utils: Provides various utility functions.
• Control.Exception: Provides functions for bracket, which is used for resource management.

runAnim = runGraphics $ indicates that the following block of code is a graphical application that will be run using the runGraphics function.

Inside the bracket expression, we open a window and define the animation loop within the lambda expression. The window is opened with the "Basic animation task" title, a size of 250x50 pixels, and DoubleBuffered for smoother animations.

createFont is used to create a font with a size of 64x28 pixels, bold, italic, and using the "courier" font.

The animation loop (loop) takes three parameters: the current text, the direction of movement (1 for right, -1 for left), and the current tick. It checks for window events and updates the direction based on button events (if the left button is pressed, the direction is reversed). Then, it updates the text graphic by moving the text in the specified direction and gets the current tick.

The loop then continues by recursively calling itself with the updated text, direction, and tick.

The runAnim function is called to run the graphical application, and when the user closes the window, the closeWindow function is called to close the window and release resources.

import Graphics.HGL.Units (Time, Point, Size, )
import Graphics.HGL.Draw.Monad (Graphic, )
import Graphics.HGL.Draw.Text
import Graphics.HGL.Draw.Font
import Graphics.HGL.Window
import Graphics.HGL.Run
import Graphics.HGL.Utils

import Control.Exception (bracket, )

runAnim = runGraphics $
 bracket
  (openWindowEx "Basic animation task" Nothing (250,50) DoubleBuffered (Just 110))
  closeWindow
  (\w -> do
    f <- createFont (64,28) 0 False False "courier" 
    let loop t dir = do
	  e <- maybeGetWindowEvent w
	  let d = case e of
		  Just (Button _ True False)  -> -dir
		  _ -> dir
	      t' = if d == 1 then last t : init t else tail t ++ [head t]
	  setGraphic w (withFont f $ text (5,10) t') >> getWindowTick w 
	  loop  t' d
	      
    loop "Hello world ! " 1  )


*Main> runAnim