public function execute($alterTemplate, callable $executor)
    {
        if ($this->alterParts) {
            $alter = sprintf($alterTemplate, implode(', ', $this->alterParts));
            $executor($alter);
        }

        $state = [];

        foreach ($this->postSteps as $instruction) {
            if (is_callable($instruction)) {
                $state = $instruction($state);
                continue;
            }

            $executor($instruction);
        }
    }