Snake ADA

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The well known game "Snake" in ADA with a safe approach, on Console (Unix) with additional features

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Build and run

Build with gprbuild:

gprbuild -d -PSnake/snake.gpr Snake/src/main.adb

Run:

./Snake/obj/main

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Features

• Set the size
• Menu
  • Change the controls
  • Set color on/off
• Pause/Play

Controls in the menu are display and can't be changed.

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Algo

var ctxt GameContext.Context = Initialisation // init the programme
var field InGame.Field = InGame.CreatField(&ctxt)
var snake InGame.Snake = InGame.CreatSnake(&ctxt)

task Keybording (Start) {
  var input char
  wait Start
  loop {
    get_immediat(&input)
    switch input {
      case ctxt.Config.Keymapped(Up): snake.ChangeDir(Up)
      case ctxt.Config.Keymapped(Down): snake.ChangeDir(Down)
      case ctxt.Config.Keymapped(Left): snake.ChangeDir(Left)
      case ctxt.Config.Keymapped(Right): snake.ChangeDir(Right)
      case ctxt.Config.Keymapped(Pause): ctxt.Game.Pause
	    case ctxt.Config.Keymapped(ExitGame): ctxt.Game.Stop(Stoped)
      case others: NOTHING
    }
  }
}

main {
  Menu(ctxt)
  field.Paint
  emit Keybording.Start
  loop {
    while ctxt.Game.Pausing {
      field.HidePt
      field.NextPt
    }
    break if !ctxt.Game.Running
    break if !field.Check(snake)
    field.DisplayPt
    snake.PrintScore
    snake.Move
    delay 0.15 second
  }
  ctxt.PrintEndGame
}

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Unimplemented additional features:

• Load your own field with a special file format
• Save the current state of your game to come back latter
• Multiple levels
• Different zoom
• Build your field
• Different snake speed

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Documentation of the Code

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Utility Pkg

type PosTerm & SizeTerm

Used to navigate on the console

Constraint: range 0 .. 100

const StartTerm : PosTerm

use to make an offset too print on the console, to be sure we don't Print at 0, because it wouldn't be visible.

type Position : record

public record that represent a position with coordinates x, y.

x : PosTerm - x coordinate.

y : PosTerm - y coordinate.

type VectorPos --> Vectors(Natural, Position).Vector

A dynamic size array of Position from generic package Ada.Container.Vectors.

type RandomPos --> Discrete_Random(PosTerm).Generator

A random generator of Position from generic package Ada.Numerics.Discrete_Random.

type ColorName

enumeration of color for the console

procedure Print_at

args:

• str : String - The things to print
• from : Position - The position to print or x, y : PosTerm - The coordinates

Print a message to the position/coordiate indicates. It interfaces a C function to handle the console navigation correctly.

procedure Print

A call to Ada.Text_io.Put

procedure MoveTo

args:

• x, y : PosTerm - The coordinate to move the cursor at.

Move the terminal cursor to the coordiante indicates. It interfaces a C function to handle the console navigation correctly.

procedure SetColor

args:

• c : ColorName - The color to set

Set the color in the console. It interfaces a C function to handle the console correctly.

procedure EraseConsole

Erase the console. It interfaces a C function to handle the console correctly.

GameContext Pkg

type Key

enumeration of the possible Key to interacte in the game.

type KeyMap

Array of Character on Key range

That type is use to binds a Character to each Key.

type ZoomIndice

Represent the zoom possible, from 1 to 3.

WARNING: zoom management is not implemented in the game

type Level

Represent the different level possible. LvCustom is supposed to be for letting the user give a file with a special format.

WARNING: level management is not implemented in the game

type GameStopedInfo

Represent the state of the game, and the reason of why the game is stoped if not Processing.

procedure displayMenu

display the menu

type Configuration tagged record

Holds the configuration of the game

(in) function Color

return Boolean

Say if the color is set of not

(in) function Zoom

return ZoomIndice

Allows to know wich zoom is set

WARNING zoom management is not implemented in the game

(in) function KeyMapped

args:

k : Key

return Character

Get the character that has been mapped to the key "k".

procedure SetUpConfig

args:

ctxt : in out Context - The context that owns the config to set up

Set up the configuration. Display a configuration panel for the user to change as he wants.

type GameInfo tagged record

Holds information about the game, and allows to interact with it.

(in) function Running

return Boolean

Say if the game is running or not.

(in) function Pausing

return Boolean

Pre => .Running

Say if the game is in pause or not.

(in out) procedure StopGame

args:

reason : GameStopedInfo - Why do we stop the game.

Pre => .Running

Post => not .Running

Stop the game through different reasons.

(in out) procedure Pause

Pre => .Running

Post => .Running and not .Pausing

Pause the game

procedure SetUpGameInfo

args:

ctxt : in out Context - The context that owns the GameInfo to set up

Set up the Game's information right befor lunching the game. Display a configuration panel for the user to select the level he wants.

WARNING: level management is not implemented in the game

? type Context tagged record

(in) function MaxWidth

return SizeTerm

Give the max width to display on the console, specify by the user.

(in) function MaxHeight

return SizeTerm

Give the max height to display on the console, specify by the user.

(in) function Config

return Configuration'Class - 'Class to make the dispatching possible

Give the configuration settings.

(in out) function Game

return access GameInfo'Class - The game information may change durring the game.

Post => .Game /= null

(in) procedure EndGame

args:

score : Integer - The score at the end of the game

Pre => not .Game.Running

Display the end of the game with the score and the reason of the lost.

function CreatContext

args:

width, height : SizeTerm - the dimention of the max size to set for the context

return Context

Post => CreatContext'Result.Game.Running

##InGame Pkg: Field Pkg and Snake Pkg

package.type Direction.Dir

A constraint integer from -2 to 2 with a value /= 0.

const Up = -1

const Down = 1

const Left = -2

const Right = 2

The logic is that it is not possible to make Up + Down nor Left + Right as 0 isn't a value; And in the snake it is not possible to switch from on direction to its opposite.

function NextPosFrom

args:

dir : in Direction.Dir

pos : Position

return Position

Post pos /= NextPosFrom'Result

Gives the next position regarding a direction.

type Snake tagged record

It represent the snake.

(in) procedure Display

Pre .Ghost.GameRunning

Display the snake.

(in out) procedure Move

Pre .Ghost.GameRunning

Post .Pos'Old /= .Pos and .Pos = NextPosFrom(.Ghost.Dir, .Pos)

Move the snake to the last direction set.

(in out) procedure Pos

args:

p : Position

Post .Pos = p

Setter of the position of the snake.

(in) function Pos

return Position

Getter of the position of the snake.

(in out) procedure ChangeDir

args:

dir : in Direction.Dir

Post Integer(.Ghost.Dir) = Integer(dir)

Change the direction of the snake.

(in out) procedure AddPoint

Post .Ghost.GameRunning and .Score = .'Old.Score + 1

Add a point to the snake, that make its length aka its score bigger.

(in) function Score

return Integer

Return the current score of the snake and its length.

function Creat

args:

ctxt : in out GameContext.Context

return Snake

Pre ctxt.Game.Running and ctxt'Unchecked_Access /= null

Creat the snake according to the game context.

type FieldElem

Enumeration used to represent the kind of the field.

function Char

args:

elem : in FieldElem

return Character

To get the represented character of the elem.

type Field tagged record

(in out) function Check

args:

s : in out Snake.Snake

return Boolean

Pre .GameRunning - the game must be running

Post .Ghost.GameRunning = (.Ghost.FieldElemAt(s.Pos) = Space) and ((.Ghost.GameRunning and then (.Ghost.FieldElemAt(f.G_PtPos) = Space and .Ghost.PtPos /= s.Pos)) or else not .Ghost.GameRunning) - FieldElemAt gives the FieldElem at the given pos, and PtPos gives the position of the point.

Check if the game can continue or if it must stope.

(in) procedure Paint

Pre .Ghost.GameRunning

Paint the field without the point.

(in) procedure DisplayPt

Pre .Ghost.GameRunning

Display the point

(in out) procedure NextPoint

Pre .Ghost.GameRunning and (.Ghost.SnakePos = .Ghost.PtPos or (.Ghost.Context /= null and then .Ghost.Context.Game.Pausing)) - Context return the context of the current game, SnakePos return the current pos of the snake

Post .Ghost.PtPos'Old /= .Ghost.PtPos and .Ghost.FieldElemAt(.Ghost.PtPos) = Space and .Ghost.PtPos /= .Ghost.SnakePos;

Set the next point on the field and ensure it is not at the place and inside the field.

(in) procedure HidePt

Pre .Ghost.GamePausing

Hide the point if we are in pause.