Computer Science Canada

Simple loop problem
Author:  x-ecutioner [ Mon Nov 24, 2008 4:44 pm ]
Post subject:  Simple loop problem
hi im trying to get my square to move from the left side to the ride side of the screen and back. the issue is, it gets to the right side and gets jammed there. i know its a simple problem but i just cant figure it out
code:

View.Set ("graphics:500,500")
View.Set ("position:middle,middle")
setscreen ("offscreenonly")
var inc : int 
  inc := 50
    loop
        if inc + 10 >= 450 then
            inc := inc - 10
        else
            inc := inc + 10
        end if
        drawfillbox (inc, 250, inc + 100, 450, 250)
        View.Update
        delay (30)
        drawfillbox (inc, 250, inc + 100, 450, 0)
        View.Update
    end loop

any ideas?
thanks for any help possible
Author:  Insectoid [ Mon Nov 24, 2008 4:54 pm ]
Post subject:  RE:Simple loop problem
Think about it.

The box is at 50. It is as 50. It adds moves right until it becomes greater than 450. It is then moved left by ten, at which point it is less than 450, so it moves right again. Hope I helped!
Author:  x-ecutioner [ Mon Nov 24, 2008 5:10 pm ]
Post subject:  RE:Simple loop problem
it definetely helped
but the question remains
how do i make it go bcak to the direction it came from
im not looking for actual code
but perhaps a suggestion on what should probably be changed :S
argh
its such a simple problem
i gotta sleep more lol
Author:  x-ecutioner [ Mon Nov 24, 2008 5:12 pm ]
Post subject:  RE:Simple loop problem
actually dont worry about thank you very much for your help:)
i decided to use for loops instead.
Author:  copthesaint [ Mon Nov 24, 2008 5:30 pm ]
Post subject:  Re: Simple loop problem
Well If you look at the code

code:
if inc + 10 >= 450 then
            inc := inc - 10
        else
            inc := inc + 10
        end if

You see that once inc will equal 450 it will continueously go back from 440 to 450.

Also if you want to do this right add a cls after the last View.Update. and delet the the white box you keep creating.

Furthermore, if you want a smoother running program then shorten the delay to 3 and decrease

inc:= inc-10
to
inc-= 1

as you see also I changed the := to -= It does the same thing to the effect you were wanting but less typing.
Author:  Insectoid [ Mon Nov 24, 2008 5:40 pm ]
Post subject:  RE:Simple loop problem
instead of using for loops, use a variable to hold the movement.
code:

var move := 1
if (box hits right wall) then
    move *= -1
elsif (box hits left wall) then
    move *= -1
inc += move


this can be shortened using the 'or' operator, I just showed the expanded version so you would know what was going on. So the box has 1 added to it, then it hits a wall. The move is flipped to negative 1. adding negative 1 is the same as subtracting positive 1, so it moves the other way.

:


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