Multi-Dimensional Array with Data Statements

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Davido01

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Joined: 28th Oct 2009

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Posted: 28th Oct 2009 14:25

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Hi, just wondering what is wrong with one of my programs I am doing from a tutorial. I think the problem is with the setting of the array but I am not sure.

Here it is:

+ Code Snippet

REM Set the parameters of the squares
REM Set Size of Square
REM Squares


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Dim S(4,4)
DIM B(4)
SelectSquare:
Print "Press 1, 2, 3 or 4"
Do
If Inkey$()="1" Then A=1 :Goto DrawSquares
If Inkey$()="2" Then A=2 :Goto DrawSquares
If Inkey$()="3" Then A=3 :Goto DrawSquares
If Inkey$()="4" Then A=4 :Goto DrawSquares
Loop

DrawSquares:
FOR N =1 TO 4
READ S(N,A)
PRINT S(N,A)
NEXT N

Wait Key

The REM at the top of the code tells you what I am trying to achieve, but I am getting stuck just on the drawing of the squares.

Any help much appreciated.

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Grog Grueslayer

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Joined: 30th May 2005

Playing: Green Hell

Posted: 28th Oct 2009 22:48

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The problem is the tutorial itself.

DATA should always be at the end of the code, it should be read all at once if you're using an array, never, ever use GOTO, and KEYSTATE() is better to use than INKEY$(). KEYSTATE() allows us to hit multiple keys at once... you may not want that now but later you'll get annoyed using INKEY$().

Here's a link to my Keystate Map:
http://mysite.verizon.net/grueslayer/Keystate.png

+ Code Snippet

REM Set the parameters of the squares
REM Set Size of Square
REM Squares

` Dimensionalize the arrays
Dim S(4,4)
DIM B(4)

` Read all data and place in the array
FOR A=1 TO 4
 FOR N=1 to 4
  READ S(N,A)
 NEXT N
NEXT A

Print "Press 1, 2, 3 or 4"
Do

 ` Go through keys 1 to 4 (keystate values)
 for t=2 to 5

  ` Check if the key is being pressed
  if keystate(t)
 
   ` Show the data
   FOR N=1 TO 4
    PRINT S(N,t-1)
   NEXT N
 
   ` Show the instructions again
   print ""
   Print "Press 1, 2, 3 or 4"
 
   ` Wait till the user lets go of all keys
   repeat
   until scancode()=0
 
  endif 
 
 next t  

Loop

end


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TDK

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Joined: 19th Nov 2002

Location: UK

Posted: 28th Oct 2009 23:03

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I agree with Grog - the tutorial you are using is dubious to say the least - it's teaching you very bad habits which will be hard to shake off.

Data statements, as Grog says, should be at the end of your program, but that's only a programming 'convention' - they will work anywhere. But conventions are conventions for a very good reason.

Try the tutorials here:

Programming Tutorials For Beginners

...in particular the 4-part series at the start.

TDK

* TDK's Web Site *

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Davido01

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Joined: 28th Oct 2009

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Posted: 29th Oct 2009 00:04 Edited at: 29th Oct 2009 01:12

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Thanks for the help. Used your nice keystate table to put keystates in and eventually worked out how to do the thing asked of me.

+ Code Snippet

REMSTART Write a program that reads the size and position of 4 squares into a multidimensional array,
and draws the square specified.  Once the square is drawn you should give the option to go back and select
                                another square or quit. REMEND

BoxData:
Dim A(4,4)

FOR X = 1 TO 4
FOR Y = 1 TO 4
READ A(X,Y)
NEXT Y
NEXT X

SelectSquare:
RESTORE BoxData
CLS
Print "Press 1, 2, 3 or 4"
Do
If keystate(2)=1 Then Y=1:Goto DrawSquares
If keystate(3)=1 Then Y=2:Goto DrawSquares
If keystate(4)=1 Then Y=3:Goto DrawSquares
If keystate(5)=1 Then Y=4:Goto DrawSquares
Loop

DrawSquares:
DIM B(4)
PRINT "Square ",Y
FOR N =1 TO 4
B(N) = A(Y,N)
NEXT N
BOX B(1), B(2), B(3), B(4)
print "Press the returnkey if you wish to print another square or space to close"
Do
If keystate(28)=1 Then GOTO SelectSquare
If keystate(57)=1 Then GOTO Close
Loop
Close:

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Wasn't quite sure what you meant by the GOTO problem though, so could you explain that a little bit more in detail please. Will look at your tutorials later TDK, and will stop using the tutorial that I am using now lol.

EDIT: Sorry didn't see your code snippet there, that is why I posted my version down with some tweaks. Can see how you get away with not using the GOTOs now.

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Grog Grueslayer

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Joined: 30th May 2005

Playing: Green Hell

Posted: 29th Oct 2009 18:03

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Quote: "Wasn't quite sure what you meant by the GOTO problem though, so could you explain that a little bit more in detail please.

EDIT: Sorry didn't see your code snippet there, that is why I posted my version down with some tweaks. Can see how you get away with not using the GOTOs now."

The main problem with GOTO is that it creates what we call Spaghetti Code (click on my signature to see the Wiki entry)... a jumbled up mess of code that's hard to track what's going on and debugging is a lot harder. GOTO forces you to use another GOTO to get back to the line you left. A better replacement is GOSUB. When you use GOSUB and you want go back to the line that sent you there use RETURN.

Your code with some changes using GOSUB instead of GOTO (with indenting to make it easier to read):

REMSTART Write a program that reads the size and position of 4 squares into a multidimensional array,
and draws the square specified.  Once the square is drawn you should give the option to go back and select
                                another square or quit. REMEND
Dim A(4,4)

FOR X = 1 TO 4
 FOR Y = 1 TO 4
  READ A(X,Y)
 NEXT Y
NEXT X

Do
 CLS
 Print "Press 1, 2, 3 or 4"
 print ""
 If keystate(2)=1 Then Y=1:Gosub DrawSquares
 If keystate(3)=1 Then Y=2:Gosub DrawSquares
 If keystate(4)=1 Then Y=3:Gosub DrawSquares
 If keystate(5)=1 Then Y=4:Gosub DrawSquares
Loop

DrawSquares:
 PRINT "Square ",Y
 BOX A(Y,1), A(Y,2), A(Y,3), A(Y,4)
 print "Press the returnkey if you wish to print another square or space to close"
 Do
  ` Check for return and EXIT the loop
  If keystate(28)=1 Then exit 
  ` Check for spacebar and END the program
  If keystate(57)=1 Then end 
 Loop
 ` Go back to the line under the GOSUB that called this routine
return

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+ Code Snippet

REMSTART Write a program that reads the size and position of 4 squares into a multidimensional array,
and draws the square specified.  Once the square is drawn you should give the option to go back and select
                                another square or quit. REMEND
Dim A(4,4)

FOR X = 1 TO 4
 FOR Y = 1 TO 4
  READ A(X,Y)
 NEXT Y
NEXT X

Do
 CLS
 Print "Press 1, 2, 3 or 4"
 print ""
 If keystate(2)=1 Then Y=1:Gosub DrawSquares
 If keystate(3)=1 Then Y=2:Gosub DrawSquares
 If keystate(4)=1 Then Y=3:Gosub DrawSquares
 If keystate(5)=1 Then Y=4:Gosub DrawSquares
Loop

DrawSquares:
 PRINT "Square ",Y
 BOX A(Y,1), A(Y,2), A(Y,3), A(Y,4)
 print "Press the returnkey if you wish to print another square or space to close"
 Do
  ` Check for return and EXIT the loop
  If keystate(28)=1 Then exit 
  ` Check for spacebar and END the program
  If keystate(57)=1 Then end 
 Loop
 ` Go back to the line under the GOSUB that called this routine
return

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Another replacement for GOTO are functions. They are the same as using GOSUB except they don't keep variables that aren't set as GLOBAL. Functions are nice to use because they can be sent specific variables/strings and return a variable/string too.

Your code with some changes using a function:

REMSTART Write a program that reads the size and position of 4 squares into a multidimensional array,
and draws the square specified.  Once the square is drawn you should give the option to go back and select
                                another square or quit. REMEND
Dim A(4,4)

FOR X = 1 TO 4
 FOR Y = 1 TO 4
  READ A(X,Y)
 NEXT Y
NEXT X

Do
 CLS
 Print "Press 1, 2, 3 or 4"
 print ""
 If keystate(2)=1 Then DrawSquares(1)
 If keystate(3)=1 Then DrawSquares(2)
 If keystate(4)=1 Then DrawSquares(3)
 If keystate(5)=1 Then DrawSquares(4)
Loop
` Always put an END before the first function (just in case the unthinkable happens)
end

function DrawSquares(Y)

PRINT "Square ",Y
 BOX A(Y,1), A(Y,2), A(Y,3), A(Y,4)
 print "Press the returnkey if you wish to print another square or space to close"
 Do
  ` Check for return and EXIT the loop
  If keystate(28)=1 Then exit 
  ` Check for spacebar and END the program
  If keystate(57)=1 Then end 
 Loop

` Go back to the line under the function call
endfunction

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+ Code Snippet

REMSTART Write a program that reads the size and position of 4 squares into a multidimensional array,
and draws the square specified.  Once the square is drawn you should give the option to go back and select
                                another square or quit. REMEND
Dim A(4,4)

FOR X = 1 TO 4
 FOR Y = 1 TO 4
  READ A(X,Y)
 NEXT Y
NEXT X

Do
 CLS
 Print "Press 1, 2, 3 or 4"
 print ""
 If keystate(2)=1 Then DrawSquares(1)
 If keystate(3)=1 Then DrawSquares(2)
 If keystate(4)=1 Then DrawSquares(3)
 If keystate(5)=1 Then DrawSquares(4)
Loop
` Always put an END before the first function (just in case the unthinkable happens)
end


function DrawSquares(Y)

 PRINT "Square ",Y
 BOX A(Y,1), A(Y,2), A(Y,3), A(Y,4)
 print "Press the returnkey if you wish to print another square or space to close"
 Do
  ` Check for return and EXIT the loop
  If keystate(28)=1 Then exit 
  ` Check for spacebar and END the program
  If keystate(57)=1 Then end 
 Loop

 ` Go back to the line under the function call
endfunction

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The way I believe is that we should learn about GOTO when we're newbies but after we learn about GOSUB and functions we should leave GOTO behind and never use it again.

Quote: "Will look at your tutorials later TDK, and will stop using the tutorial that I am using now lol."

Yeah, TDK's tutorials are top notch... read them all even if you think you know everything about a command.

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