var existsWin1 = 0
var step = 0
var qStep = 0
var qNum
var probNum

tested=new Array(1,0,0,0,0)
testedQ=new Array(5)
testedQ[1]=new Array(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)
testedQ[2]=new Array(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)
testedQ[3]=new Array(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)
testedQ[4]=new Array(0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)

answers=new Array(5)
answers[1]=new Array(1,0,-1,0,3,0,-2,-0.5,3,0,0,0,0,-1,-1,0,2,-3,-1)
answers[2]=new Array(1,2,2,1,4,0,0,0,-1,-1,-1,1,-2,2,-1,-1,-1,-1,-1)
answers[3]=new Array(1,0,1,1,7,0,2,0.5,2,2,1.5,3,3.5,1,1,1,2,1.5,1.5)
answers[4]=new Array(1,0,1,0,-5,0.5,1,1,-1,0,0,0,0,2,-1,-1,1,0,0)

limitDNE=new Array(5)
limitDNE[1]=new Array(1,1,0,1,0,1,0,0,0,1,1,1,1,0,0,1,0,0,0)
limitDNE[2]=new Array(1,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,0)
limitDNE[3]=new Array(1,1,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0)
limitDNE[4]=new Array(1,1,0,0,0,0,0,0,0,1,0,0,1,0,0,0,0,0,0)

Tf = new Array(5)
for(var i=1;i<5;i++){
 Tf[i] = new Image()
 Tf[i].src = "graph"+i+"f.gif"
}

Tg = new Array(5)
for(var i=1;i<5;i++){
 Tg[i] = new Image()
 Tg[i].src = "graph"+i+"g.gif"
}

Tq = new Array(19)
for(var i=1;i<19;i++){
  Tq[i] = new Image()
  Tq[i].src = ""+i+".gif"
}

function closeWin() {
  onerror=null
  if (existsWin1==1) {win1.close()}
}

function pickNew(){
  if (step < 4) {
    with(Math){
      probNum=floor(4*random())+1
      if (tested[probNum]) {
        b=1
        while (tested[b]) {b++}
        probNum=b
      }
      tested[probNum]=1
    }
    step++
    document.graphf.src=Tf[probNum].src
    document.graphg.src=Tg[probNum].src
  }
}

function pickProblem(){
  if (qStep == 18) {
    if (step < 4) { 
      qStep = 0
      pickNew()
    }
    else {document.limitProblem.nextLimit.value="Done!"}
  }
  if (qStep < 18){
    with(Math){    
      qNum=floor(18*random())+1
      if (testedQ[probNum][qNum]) {
        b=1
        while (testedQ[probNum][b]) {b++}
        qNum=b
      }
      testedQ[probNum][qNum]=1
    }
    qStep++
    document.graphq.src=Tq[qNum].src
  }
}

function checkAns(){
  if ((limitDNE[probNum][qNum]&&document.limitProblem.DNE.checked)
       ||(!(limitDNE[probNum][qNum])&&!(document.limitProblem.DNE.checked))) {
    if(!(limitDNE[probNum][qNum])){
      ans = parseFloat(document.limitProblem.exists.value)
      if (ans==answers[probNum][qNum]){
        alert("Your answer is correct!")
      }
      else {       
        alert("You calculated the limit incorrectly. Try again!")
      }
    }
    else{
      document.limitProblem.exists.value=""
      alert("Your answer is correct!")
    } 
  }
  else {
    document.limitProblem.exists.value=""
    alert("Your answer is wrong.  Try again!")
  }
}