IPhone : EXC_BAD_INSTRUCTION runtime error when attempting to calculate

so im making a simple app to calculate simple values inputted by the user and some values already in the app but i keep getting this runtime error every time i try to calculate the result

here is the code:

    for(var i = 0; i<name.count; i++){
        if name[i] == typeFood{
            yieldOutput == percent[i]
            mycalc=percent[i] / 100.0
        }
    }

    yieldOutput.text = String (format:"%.2f", percent )
    var portionSize = typeDesired.text.toInt()! / typeOriginal.text.toInt()!
    var myint:Int=typeAmount.text.toInt()!
    var myres:Double=Double(myint)*(mycalc)*Double(portionSize)
    amountOutput.text =  String (format:"%.2f", myres)
    self.typeDesired.resignFirstResponder()

i get the error on line

  var myres:Double=Double(myint)*(mycalc)*Double(portionSize)