Computer Science Canada

How do I add multiple rows of enemies in Space Invaders using an Array or loop?
Author:  Memebot [ Wed Apr 26, 2017 8:27 pm ]
Post subject:  How do I add multiple rows of enemies in Space Invaders using an Array or loop?
[size=14][b]What is it you are trying to achieve?[/b][/size]
Make More than 1 Row of enemy Appear

[size=14][b]Post any relevant code (You may choose to attach the file instead of posting the code if it is too long)[/b][/size]

This is the code which we set up in class, we haven't got to the bombs/bullets clashing with the enemies yet, I just wish to figure out the lines of code to make more than 1 row appear

%Set up the screen with how you want it to look
setscreen ("graphics:max,max") %Width & Height

const WIDTH : int := 1170
const HEIGHT : int := 830
setscreen ("graphics:" + intstr (WIDTH) + ";" + intstr (HEIGHT) + ",position:bottom:center,nobuttonbar,title:Space Invaders")

%read the picture files into a variable ID
var backgroundID : int := Pic.FileNew ("background.jpg")
var shipID : int := Pic.FileNew ("ship.bmp")
var bulletID : int := Pic.FileNew ("bombD.gif")
var alienID : int
var alienID1 : int := Pic.FileNew ("bicho.gif")
var alienID2 : int := Pic.FileNew ("bicho0.gif")
var alienID3 : int := Pic.FileNew ("bicho1.gif")


%Allow up to 15 bullets at one time
var bulletX : array 1 .. 15 of int := init (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
var bulletY : array 1 .. 15 of int := init (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
var currentTime, bulletTime : int
sysclock (bulletTime)

% initialize the starting point for the row of aliens
var alienX : array 1 .. 16 of int := init (310, 350, 390, 430, 470, 510, 550, 590, 630, 670, 710, 750, 790, 830, 870, 910)
var alienY : int := 850
var alienDir : int := 1
var pictureCtr, picture : int := 1


%display the background picture
Pic.Draw (backgroundID, 0, 0, picCopy)

%Merge the "ship" onto the background at a specified x,y location
var y : int := 10
var x : int := floor (WIDTH / 2)
Pic.Draw (shipID, x, y, picMerge)

%Shoot procedure
procedure shoot ()
%find a free spot to begin another bullet
for i : 1 .. 15
if bulletX (i) = 0 then
bulletX (i) := x + 43
bulletY (i) := y + 60
sysclock (bulletTime)
exit
end if
end for
end shoot

%Play game
procedure playGame ()
%capture the arrow key inputs and reposition the ship on the background
var chars : array char of boolean
loop
Input.KeyDown (chars)
if chars (KEY_RIGHT_ARROW) then
x := x + 5
if x >= WIDTH then
x := 0
end if
end if
if chars (KEY_LEFT_ARROW) then
x := x - 5
if x <= 0 then
x := WIDTH
end if
end if
if chars (KEY_UP_ARROW) then
y := y + 5
if y >= HEIGHT then
y := 0
end if
end if
if chars (KEY_DOWN_ARROW) then
y := y - 5
if y <= 0 then
y := 0
end if
end if
if chars (' ') then
sysclock (currentTime)
if currentTime - bulletTime >= 200 then
shoot ()
end if
end if
if pictureCtr >= 6 then % time to switch pictures
if picture < 2 then
picture := picture + 1
else
picture := 0
end if
pictureCtr := 1
else
pictureCtr := pictureCtr + 1
end if
% Load the chosen picture of the alien
case picture of
label 1 :
alienID := alienID1
label 2 :
alienID := alienID2
label 3 :
alienID := alienID3
label 4 :
alienID := alienID2
label :
alienID := alienID3
end case
%determine if aliens are at an edge
%if so, switch directions & move down
if alienX (16) >= WIDTH - 15 or alienX (1) < 5 then
alienDir := alienDir * (-1)
alienY := alienY - 30
end if
%draw background, then ship,then aliens, then bullets
Pic.Draw (backgroundID, 0, 0, picMerge)
Pic.Draw (shipID, x, y, picMerge)
for i : 1 .. 16
alienX (i) := alienX (i) + alienDir
if alienX (i) not= 0 then
Pic.Draw (alienID, alienX (i), alienY, picMerge)
end if
end for
for i : 1 .. 15
if bulletY (i) not= 0 then
if bulletY (i) + 3 < maxy then
bulletY (i) := bulletY (i) + 5
Pic.Draw (bulletID, bulletX (i), bulletY (i), picMerge)
else
bulletX (i) := 0
bulletY (i) := 0
end if
end if
end for
View.Update
end loop
end playGame



%Play the game procedure
playGame ()


[/syntax]

[size=14][b]Please specify what version of Turing you are using[/b][/size]
I believe we are using 4.1 in class.
Author:  Insectoid [ Fri Apr 28, 2017 2:20 pm ]
Post subject:  RE:How do I add multiple rows of enemies in Space Invaders using an Array or loop?
You''re already using an array to store your enemies so you're halfway there. You already know that if you need a bunch of a thing, you keep them in an array. What do we want now? A bunch of rows. A row is a thing though, right? So if we want a bunch of rows, it makes sense to store them in an array!

Since an array can be of any type, and an array is itself a type, we can make an array of arrays!
code:
var foo : array 1..5 of array 1..5 of int


This array contains 5 cells, each of which is itself an array of length 5. You access elements in the array pretty much as you'd expect:
code:
a := foo (2)(3)


This will return the 3rd element of the 2nd element of foo.

Now you need to write some code that works on arrays of arrays. I'll leave that up to you, but I'll give you a hint: Arrays of arrays play really nice with loops inside loops.

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