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Author Topic: how to set part of a 2dimensional array(boolean) to true?  (Read 1529 times)

waituntilthis

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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

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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

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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

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Re: how to set part of a 2dimensional array(boolean) to true?
« Reply #3 on: November 12, 2019, 01:49:47 pm »
THE SOLUTION for future readers;

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!

Thaddy

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Re: how to set part of a 2dimensional array(boolean) to true?
« Reply #4 on: November 12, 2019, 01:53:11 pm »
THE SOLUTION for future readers;

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.  8-)
Use the language and know the language.
« Last Edit: November 12, 2019, 02:06:18 pm by Thaddy »
Specialize a type, not a var.

waituntilthis

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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

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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
Look at Post #3 (Reply-2)
Eugene shows a method to directly access an array-member via its pointer
One System to rule them all, One Code to find them,
One IDE to bring them all, and to the Framework bind them,
in the Land of Redmond, where the Windows lie
---------------------------------------------------------------------
Code is like a joke: If you have to explain it, it's bad

Handoko

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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
More info: https://en.wikipedia.org/wiki/Tetris#Gameplay
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 »

 

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