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### Author Topic: how to set part of a 2dimensional array(boolean) to true?  (Read 592 times)

#### waituntilthis

• New Member
• Posts: 24
##### how to set part of a 2dimensional array(boolean) to true?
« on: November 12, 2019, 11:00:35 am »
hi all,

I'm currently working on tetris and I've built 2 rasters. they are twodimensional arrays and are horizontal(x) 0..9 and vertical (y)0..19.
when a block hits the ground, it stays there and a new one spawns up top. problem is that I need my second raster (array -filled) to set those 'coordinates' to 1, so that blocks can detect where blocks are currently residing.

thing is, I'm very lost on how to tell my twodimensional array that filled[x,y] should be true. I only get illegal qualifiers.

here's my code....
Code: Pascal  [Select][+][-]
1.
2.   private
3.     blockwait, bottomcheck, movement, x, y: integer;
4.     start, filled: boolean;
5.     location: array[0..9, 0..19] of integer;
6.   public
7.
8.   end;
9.
10. var
11.   Form1: TForm1;
12.   filled: array[0..9, 0..19] of boolean;
13.
14. implementation
15. -------------------------------------------
16.
17. procedure tform1.createblock();
18. var
19.   a,b:integer;
20.   img : Timage;
21. begin
22.   x:=4;
23.   y:=0;
24.   img:= timage.create(application);
25.   img.top:=y*50;
26.   img.left:=x*50;
27.   img.visible:=true;
28.   img.picture:=fallingblock.picture;
29.   img.stretch:=true;
30.   img.width:=50;
31.   img.height:=50;
32.   img.enabled:=true;
33.   img.transparent:=true;
34.   img.Parent:=fallingblock.parent;
35.   fallingblock:=img;
36.   img.top:=a;
37.   img.left:=b;
38.   //i tried converting the coordinates from x, to img.left,to b, so that filled would hopefully stay in one place instead
39.   //of moving around the field attached to a falling block.
40.   filled[a,b]:=true;
41. end;
42.
43. ------------------------------
44.
45. //if a block hits the bottom procedure createblock is called, I still have to write code for the falling block hitting a filled:=true but i'm currently stuck.
46. procedure TForm1.blockfallingTimer(Sender: TObject);
47. begin
48. y:=y+1;
49. fallingblock.top := 50 * y;
50. if y>=19 then
51. begin
52.   y:=0;
53.   createblock();
54. end;
55. end;
56.

#### Handoko

• Hero Member
• Posts: 3653
• My goal: build my own game engine using Lazarus
##### Re: how to set part of a 2dimensional array(boolean) to true?
« Reply #1 on: November 12, 2019, 11:36:22 am »
Glad to find someone want to use Lazarus to create games.

I'm not here to answer your question, but I recommend you read my tutorial for snake game:
https://forum.lazarus.freepascal.org/index.php/topic,38136.15.html

Honesty, the tutorial in the link above is very long and boring. But if you follow it seriously to the end, you'll be sure to learn:

- Game loop
- User input detection
- Using array to represent the the game world
- Collision detection
- How to use TList (to replace array)
- Using buffer for keyboard input
- Using buffer to reduce flickering

Also if you are a beginner in Lazarus game programming, I recommend you to read the post in the link below, which has many useful examples:
https://forum.lazarus.freepascal.org/index.php/topic,43474.msg304278.html#msg304278

#### waituntilthis

• New Member
• Posts: 24
##### Re: how to set part of a 2dimensional array(boolean) to true?
« Reply #2 on: November 12, 2019, 11:49:35 am »
handoko thanks for your reply! will read it but i'm not sure that I can find my solution very efficiently that way, i'm quite new to free pascal

#### waituntilthis

• New Member
• Posts: 24
##### Re: how to set part of a 2dimensional array(boolean) to true?
« Reply #3 on: November 12, 2019, 01:49:47 pm »

I found out that I accidentally changed filled from a Boolean array to just a single Boolean. I wanted to make sure that my array was false for the entire raster and I used: Filled:=false;
after using filled:=false I got an error asking me to change filled to Boolean so I did just that in my private declaration: filled:boolean;. wich gave me illegal qualifiers w/o explanation. it's working now!

• Hero Member
• Posts: 10290
##### Re: how to set part of a 2dimensional array(boolean) to true?
« Reply #4 on: November 12, 2019, 01:53:11 pm »

I found out that I accidentally changed filled from a Boolean array to just a single Boolean. I wanted to make sure that my array was false for the entire raster and I used: Filled:=false;
after using filled:=false I got an error asking me to change filled to Boolean so I did just that in my private declaration: filled:boolean;. wich gave me illegal qualifiers w/o explanation. it's working now!

You can use the Default() intrinsic to set a whole array to false... did you know that?
Example:
Code: Pascal  [Select][+][-]
1. {\$mode objfpc}{\$H+}
2. type
3.   TMyArray = array[0..99, 0..99] of byte; // whatever dimension and type
4. var
5.   a:TMyArray;
6. begin
7.   a:= Default(TMyArray); // array is all zero'd. One liner.
8. end.
Actually, for future readers, pay attention to a "slightly" more correct solution.
Use the language and know the language.
« Last Edit: November 12, 2019, 02:06:18 pm by Thaddy »
I am more like donkey than shrek

#### waituntilthis

• New Member
• Posts: 24
##### Re: how to set part of a 2dimensional array(boolean) to true?
« Reply #5 on: November 12, 2019, 02:54:50 pm »
no thaddy I didn't know that! thanks

#### Zvoni

• Sr. Member
• Posts: 373
##### Re: how to set part of a 2dimensional array(boolean) to true?
« Reply #6 on: November 12, 2019, 03:02:07 pm »
It still doesn't solve his initial problem: how to set a part of an array to True

Found this here:
https://forum.lazarus.freepascal.org/index.php?topic=38602.0
Eugene shows a method to directly access an array-member via its pointer
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One Code to bring them all, and to the Framework bind them,
in the Land of Redmond, where the Windows lie
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#### Handoko

• Hero Member
• Posts: 3653
• My goal: build my own game engine using Lazarus
##### Re: how to set part of a 2dimensional array(boolean) to true?
« Reply #7 on: November 12, 2019, 03:54:45 pm »
I haven't fully read the OP question. Was it a Tetris game? If yes, then the code OP showed us has many missing parts:

- Standard Tetris has 7 tetrominos
OP need to create a container to store all the tetromino data. It can be a list of TList of x/y points, a list of 2 dimensional array of Boolean, array[0..6] of TList, array[0..6] of 2 dimentional array of Boolean or whatever s/he feels convenient.

- Global variables
It should store the value of Current_Tetromino_Model and Current_Tetromino_Rotation

To check if the tetromino need to respawn:
If (Current_Tetromino_Y <= 0) or DetectCollision(Current_Tetromino_Model, Current_Tetromino_Rotation, Current_Tetromino_Position) then

And this how the DetectCollision works:
1. Get the tetromino data that stored previously in the container based on Current_Tetromino_Model
2. Rotate the data based on the Current_Tetromino_Rotation
3. Move the tetromino based on Current_Tetromino_Position
4. Compare the final result with the game world, if right below the each of the tetromino's blocks are empty then it Return := False; (which means it is not blocked)

And if you want each tetromino to has its own color, thing will become a bit more complicated.

Sorry to say, but I think creating a Tetris game is too hard for the OP. It is lots easier to create a snake game, which is much simpler.

Anyway, I remember a senior here Eny ever posted a Tetris game, he named it Petris. It was about 600 LOC, well written. You can try to search it if you want to see the source code.
« Last Edit: November 12, 2019, 03:59:29 pm by Handoko »