<?php
// Calculator.php
class Calculator {
    public function getNumberFromUserInput() {
        // complicated function to get number from user input
    }

    public function printToScreen($value) {
        // another complicated function
    }

    public function divideBy($num2) {
        if ($num2 == 0) return NAN;
        return $this->getNumberFromUserInput()/$num2;
    }

    public function divideByAndPrint($num2) {
        if ($num2 == 0) $this->printToScreen("NaN");
        $this->printToScreen($this->getNumberFromUserInput()/$num2);
    }
}