Computer Science Canada

lightBike help
Author:  evildaddy911 [ Mon Nov 07, 2011 4:04 pm ]
Post subject:  lightBike help
What is it you are trying to achieve?
basic lightbikes program


What is the problem you are having?
im having trouble adding a powerup that makes your trial longer,
the 'shift' procedure says "array subscript is out of range"


Describe what you have tried to solve this problem
<Answer Here>


Post any relevant code (You may choose to attach the file instead of posting the code if it is too long)
see below

Please specify what version of Turing you are using
4.1.1
Author:  Zren [ Mon Nov 07, 2011 5:16 pm ]
Post subject:  RE:lightBike help
Turing:

    for decreasing b : upper (y) .. 2   % moves bike trail forward
        x (b) := x (b - 1)
        y (b) := y (b - 1)
        x2 (b) := x2 (b - 1)
        y2 (b) := y2 (b - 1)
    end for


What happens when the players lightbike's trail is longer than the computers?
Eg:
y : array 1..60
y2 : array 1..50
Author:  evildaddy911 [ Mon Nov 07, 2011 5:55 pm ]
Post subject:  Re: lightBike help
it crashes, so i changed it to
Turing:
    for decreasing b : upper (y) .. 2   % moves bike trail forward
        x (b) := x (b - 1)
        y (b) := y (b - 1)
    end for
    for decreasing m : upper (y2) .. 2
        x2 (m) := x2 (m - 1)
        y2 (m) := y2 (m - 1)
    end for


but it still crashes and points to the drawing trail part. i did the same thing to it:
Turing:
    for c : 2 .. upper (x)
        drawfilloval (x (c), y (c), 3, 3, brightblue)             % draws trails
    end for
    for n : 2 .. upper (x2)
        drawfilloval (x2 (n), y2 (n), 3, 3, brightgreen)
    end for

now it works, thanks a lot!
Author:  Zren [ Tue Nov 08, 2011 2:04 am ]
Post subject:  RE:lightBike help
Just so you know, there's no reason you can't use the same variable name for each of the for loops. The variable is only decalared in the scope of the loop.

Example:
Turing:

    % i hasn't been declared
    for i : 67 .. 69
        put i
    end for
    % put i would fail here as i has been unreferenced (undeclared) as it's outside the scope the variable was declared in.
    for i : 1 .. 100
         put i
    end for
    % put i would fail here as i has been unreferenced (undeclared).


That is perfectly legal code, as the variable i has been undeclared as it leaves the scope of the for loop.

A coding standard is to use i as a counter instead of a random variable name if nothing is more suitable (Eg: x, and y would be more suitable if looping over a all pixels on the screen).

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