errant/tacit

<?php
namespace Tacit\Instruction;
/**
 * Represents a binary operation
 *
 * Pops two items from the stack, transforms them
 * and pushes the resule back onto the stack
 *
 * @author Tom Morton
 */
class BinaryOperation extends \Tacit\Instruction {

    public function execute($vm)
    {
        $left = $vm->stack->pop();
        $right = $vm->stack->pop();
        $value = $this->transform($left, $right);
        $vm->stack->push($value);
    }

    public function transform($left, $right)
    {
        throw new \Exception('Instruction Error: instruction does not implement transform');
    }
}