Qt Quick Demo - Calqlatr

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 ** This file is part of the examples of the Qt Toolkit.
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 var curVal = 0
 var memory = 0
 var lastOp = ""
 var previousOperator = ""
 var digits = ""

 function disabled(op) {
     if (digits == "" && !((op >= "0" && op <= "9") || op == "."))
         return true
     else if (op == '=' && previousOperator.length != 1)
         return true
     else if (op == "." && digits.toString().search(/\./) != -1) {
         return true
     } else if (op == "√" &&  digits.toString().search(/-/) != -1) {
         return true
     } else {
         return false
     }
 }

 function digitPressed(op)
 {
     if (disabled(op))
         return
     if (digits.toString().length >= display.maxDigits)
         return
     if (lastOp.toString().length == 1 && ((lastOp >= "0" && lastOp <= "9") || lastOp == ".") ) {
         digits = digits + op.toString()
         display.appendDigit(op.toString())
     } else {
         digits = op
         display.appendDigit(op.toString())
     }
     lastOp = op
 }

 function operatorPressed(op)
 {
     if (disabled(op))
         return
     lastOp = op

     if (op == "±") {
             digits = Number(digits.valueOf() * -1)
             display.setDigit(display.displayNumber(digits))
             return
         }

     if (previousOperator == "+") {
         digits = Number(digits.valueOf()) + Number(curVal.valueOf())
     } else if (previousOperator == "−") {
         digits = Number(curVal.valueOf()) - Number(digits.valueOf())
     } else if (previousOperator == "×") {
         digits = Number(curVal) * Number(digits.valueOf())
     } else if (previousOperator == "÷") {
         digits = Number(curVal) / Number(digits.valueOf())
     }

     if (op == "+" || op == "−" || op == "×" || op == "÷") {
         previousOperator = op
         curVal = digits.valueOf()
         digits = ""
         display.displayOperator(previousOperator)
         return
     }

     if (op == "=") {
         display.newLine("=", digits.valueOf())
     }

     curVal = 0
     previousOperator = ""

     if (op == "1/x") {
         digits = (1 / digits.valueOf()).toString()
     } else if (op == "x^2") {
         digits = (digits.valueOf() * digits.valueOf()).toString()
     } else if (op == "Abs") {
         digits = (Math.abs(digits.valueOf())).toString()
     } else if (op == "Int") {
         digits = (Math.floor(digits.valueOf())).toString()
     } else if (op == "√") {
         digits = Number(Math.sqrt(digits.valueOf()))
         display.newLine("√", digits.valueOf())
     } else if (op == "mc") {
         memory = 0;
     } else if (op == "m+") {
         memory += digits.valueOf()
     } else if (op == "mr") {
         digits = memory.toString()
     } else if (op == "m-") {
         memory = digits.valueOf()
     } else if (op == "backspace") {
         digits = digits.toString().slice(0, -1)
         display.clear()
         display.appendDigit(digits)
     } else if (op == "Off") {
         Qt.quit();
     }

     // Reset the state on 'C' operator or after
     // an error occurred
     if (op == "C" || display.isError) {
         display.clear()
         curVal = 0
         memory = 0
         lastOp = ""
         digits = ""
     }
 }