mathlib demo 'IsOnRight'

main.lua

require("mathlib")
 
gameBoard = display.newGroup()
 
screenW = display.contentWidth
screenH = display.contentHeight
centerX  = display.contentWidth/2
centerY = display.contentHeight/2
local mRand = math.random
 
local object1 = display.newCircle(gameBoard, 0, centerY, 10)
gameBoard:insert(object1)
 
-- Set up our point data...
north = display.newCircle(mRand(0,screenW),0,20)
south = display.newCircle(mRand(0,screenW),screenH,20)
 
-- Draw line using the above data...
local tempLine = display.newLine(gameBoard, north.x, north.y, south.x, south.y)
tempLine:setColor(0, 255, 0)
 
----------------------------------------------------------------
-- MAIN LOOP
----------------------------------------------------------------
local function Main( event )
     -- Continuously check to see if point has crossed
     -- over to the right side of our test points' line...
     if(isOnRight( north,south, object1 )) then
          tempLine:setColor(255, 0, 0)  
     else
          tempLine:setColor(0, 255, 0)
     end
     object1.x = object1.x + 2
end
 
Runtime:addEventListener( "enterFrame", Main )