calculateQuantity example

$this->prices->clear();

        $rules = $this->context->buildTaxRules($this->product->get('taxId'));

        foreach ($mapped as $quantity => $price) {
            $value = $this->getPriceForTaxState($price, $this->context);

            $definition = new QuantityPriceDefinition($value, $rules, $quantity);

            $this->prices->add(
                $this->priceStubs->calculateQuantity($definition, $this->context)
            );
        }
    }

    /** * @internal */
    public function getIterator(): \Traversable
    {
        return new \ArrayIterator(
            $this->prices->map(function DCalculatedPrice $price) {
                

        if ($price instanceof PriceCollection) {
            $value = $this->getPriceForTaxState($price, $this->context);

            $definition = new QuantityPriceDefinition(
                $value,
                $this->price->getTaxRules(),
                $this->getQuantity()
            );

            $price = $this->priceStubs->calculateQuantity($definition, $this->context);
        }

        if (!$price instanceof CalculatedPrice) {
            throw ProductException::invalidCheapestPriceFacade($this->item->getUniqueIdentifier());
        }

        $this->price->overwrite(
            $price->getUnitPrice(),
            $price->getTotalPrice(),
            $price->getCalculatedTaxes(),
        );

        

    public function discount(float $value): void
    {
        $definition = new QuantityPriceDefinition($this->price->getUnitPrice(), $this->price->getTaxRules());
        $definition->setIsCalculated(true);

        $unit = $this->priceStubs->calculateQuantity($definition, $this->context);

        $discount = $this->priceStubs->calculatePercentage(\abs($value), new CalculatedPriceCollection([$unit]), $this->context);

        $definition = new QuantityPriceDefinition(
            $this->price->getUnitPrice() - $discount->getUnitPrice(),
            $this->price->getTaxRules(),
            $this->getQuantity()
        );

        $this->overwrite($definition);
    }