cozylife/hackfastalgos

<?HH
/**
 * Hack Fast Algos
 *
 * Implementation of Polish Prefix Notation
 * Learn more @link https://en.wikipedia.org/wiki/Polish_notation
 */

namespace HackFastAlgos;

class PolishNotation
{
    private array $math = [];
    private Vector<float> $stack = Vector{};

    public function __construct(string $math){
        $this->math = explode(' ', $math);
    }

    public function toFloat() : float
    {
        $length    = count($this->math);
        for ($i = $length-1; $i >= 0; $i--) {

            $item = $this->math[$i];
            switch ($item) {

                case ' ':
                    continue;
                    break;

                case is_numeric($item):
                    $this->addFloatNumberToStack((float) $item);
                    break;

                default:
                    $this->calculateAndAddToStack($item);
                    break;

            }

        }

        return $this->stack->pop();
    }

    private function addFloatNumberToStack(float $number)
    {
        $this->stack[] = $number;
    }

    private function calculateAndAddToStack(string $operator)
    {
        $operand1 = $this->stack->pop();
        $operand2 = $this->stack->pop();
        $this->addFloatNumberToStack($this->calculateWithStringOperator($operator, $operand1, $operand2));
    }

    private function calculateWithStringOperator(string $operator, float $num1, float $num2) : float
    {
        switch ($operator) {

            case '+':  return $num1 +  $num2;
            case '-':  return $num1 -  $num2;
            case '*':  return $num1 *  $num2;
            case '/':  return $num1 /  $num2;
            case '%':  return $num1 %  $num2;
            case '**': return $num1 ** $num2;

        }
    }
}