Computer Science Canada

pixel graphics program (swapping)
Author:  slimshadyy [ Mon Apr 22, 2013 6:55 pm ]
Post subject:  pixel graphics program (swapping)
What is it you are trying to achieve?

create 4 filled circles side by side with these colours: red, green, yellow, blue (from left to right). if the user presses g or G the colours should start to cycle and continue even if the user doesnt press anything. if the user presses S or s, then stop cycling. if the user presses x or X, then exit the program.
hint: you will need a variable startStop to keep track of whether the colours should cycle or not.


What is the problem you are having?

i cant get the program to stop cycling when i press s or S. i dont really know how to do the startStop thing.


Describe what you have tried to solve this problem

i tried to write the code for it but i think its wrong. nothing shows up on the run screen.


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

var c1 : int := 12
var c2 : int := 2
var c3 : int := 14
var c4 : int := 9
var swap : int
var input : string (1) := ' '
var run : int := 0
var startStop : int := 0

loop
if hasch then
getch (input)
if input = 'g' or input = 'G' then
run := 1
if input = 's' or input = 'S' then
startStop := 0
else
run := 0
startStop := 1
end if
end if
if run = 1 and startStop = 0 then
drawfilloval (100, 100, 20, 20, c1)
drawfilloval (200, 100, 20, 20, c2)
drawfilloval (300, 100, 20, 20, c3)
drawfilloval (400, 100, 20, 20, c4)
delay (500)
swap := c1
c1 := c2
c2 := c3
c3 := c4
c4 := swap
end if
end if
exit when input = 'x' or input = 'X'
end loop
put "Goodbye"

Turing:






Please specify what version of Turing you are using

4.1.1
Author:  Raknarg [ Mon Apr 22, 2013 6:59 pm ]
Post subject:  RE:pixel graphics program (swapping)
Turing:

if input = 'g' or input = 'G' then
            run := 1
            if input = 's' or input = 'S' then
                startStop := 0
            else
                run := 0
                startStop := 1
            end if
        end if


How is that second if statement ever supposed to run?
Author:  slimshadyy [ Mon Apr 22, 2013 7:02 pm ]
Post subject:  Re: pixel graphics program (swapping)
oh true. so do i put all as one statement?
Author:  Raknarg [ Mon Apr 22, 2013 7:04 pm ]
Post subject:  RE:pixel graphics program (swapping)
Sure. They're different conditions for the same event, basically. If you press g, do this. Otherwise, if you press s, do this. Otherwise, if it's anything else, do this.
Author:  slimshadyy [ Mon Apr 22, 2013 7:06 pm ]
Post subject:  Re: pixel graphics program (swapping)
but they are 2 different variables. if you press g or s, it can never be both. only one or the other. so how would u put it in one statement.
Author:  Raknarg [ Mon Apr 22, 2013 7:13 pm ]
Post subject:  RE:pixel graphics program (swapping)
Were you ever taught elsif before?

If not I'll give you a breakdown:

Turing:

if a = true then
     do_a()
elsif b = true then
     do_b()
elsif c = true then
     do_c()
else
     do_d()
end if


This is how it will run. First, it will see if condition a is true (could be if a certain key is pressed, or a variable is a vertain value). If it's true, it'ss do something. Otherwise, if b is true, it'll do something else. Otherwise, if c is true, it'll do something else. Otherwise, it'll do_d().

The order matters. If both a and b are true, it will do whatever is in a, and then exit the if. You can't do two conditions in an if statement. This is what you're looking for.
Author:  slimshadyy [ Mon Apr 22, 2013 7:21 pm ]
Post subject:  Re: pixel graphics program (swapping)
okay thanks i figured it out Smile

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