combinatorics – From a bag of n balls, with c colours, and d draws count how many variations are possible?

First, the objective is not to use formulas for combinations, or permutations.
The objective is to use loops(for, while, etc.) to make mathematica count the number of possible variations/sequences of the following situation:

Let’s assume we have a bag with $n$ balls, with $c$ different colours, and $d$ draws from the bag. There is no replacement, and you can consider separately the case when the order is important, and when it’s not.

For this question, I appreciate readability more than efficiency.

calculus of variations – epsilon delta proof of limit

I am trying to learn the epsilon delta proof of limit. I am a little confused why we always consider that epsilon>0, like if the discontinuity point of the graph is below the x axis, then nearest value or range to limit will also be in the negative part, in that case value of epsilon will be smaller than zero.

8 – “Order items” view displaying removed items (variations)?

I’m dynamically removing items from cart with this function:

  static function _remove_product_variation_from_cart($variationId) {
    $orders = Drupal::service('commerce_cart.cart_provider')->getCarts();
    if (empty($orders)) {
      return 0;
    $items = reset($orders)->getItems();

    foreach ($items as $item) {
      $quantity = $item->getQuantity();
      $itemVariationId = $item->getPurchasedEntity()->id();
      if ($variationId == $itemVariationId){
        foreach ($orders as $order) {
        return $quantity;
    return 0;

And during checkout process it’s all fine – removed items are not displayed. But page:


is listing also removed items (that’s view “Order items”). Sum (order total) is correct however.
On other hand i.e. view “Checkout Order Summary” is returning order items correctly (without removed ones).

Am I removing cart item wrong way or something? Why is this happening?

calculus of variations – Are these two subsets of matrices rank-$1$ connected?

Let $s>0$ be a positive number (in my application $s>frac{1}{2}$, but I am not sure if it matters here). Let $M_2$ be the set of all real $2 times 2$ matrices, and define the following sets:

$$X={ A in M_2 , |, det A=s^2 ,text{and },sigma_1(A)=sigma_2(A)=s }, , ,,,,Y={ A in M_2 , |, sigma_1(A)=0, sigma_2(A)=1 },$$

where $sigma_1(A) le sigma_2(A)$ are the singular values of $A$.

(The point of the condition $det A=s^2$ in the definition of $X$ is to make $det A$ positive, i.e. to exclude $det A=-s^2$).

Question: Do there exist $A in X, B in Y$ such that $A-B$ has rank $1$?

seo – Do performance variations based on locations result in different rankings in different locations?

My server is located in the US. I get visitors from both US and the countries outside the US. The “time to first byte” is around 300 ms in the US. But when I test from an Australian or Indian location, the first-byte time is about 1 sec. Probably network latency is affecting the response times. Do such performance variations affect search engine rankings (especially that of Google and Bing) in different locations? Can search engines rank my site higher in the US over the other countries?

woocommerce – Save and reuse product variations

Does anyone know of a plugin or a method that would allow me to create a set of variations with a quantity and set the price. From there save this variation set to be reused in one option, and the only change from there will be to adjust the quantity and price? Someone suggested Gravity forms but I am not familiar with that plugin to tell how it could be used to achieve what I need.

Show Price Only When All Variations Have Been Selected [closed]

Currently, price is show in a single product page. I would like to hide it and make it appear only after customer has selected all the variations available.

I have tried the code in this question but it does not work for me.

WooCommerce Variations Table Plugin – Social Media Marketing (SMM)

WooCommerce variation table plugin shows your store products in a data table so the user can easily filter and sort the product they need. WooCommerce variations table plugin enables you to select field options with a dynamic table that allows users to find products by color, size, and style. It allows your customers to copy, print, or export the list of product variations to review offline. Customers can download the table in CSV, Excel, or PDF format. The price of this extension is just $49 with a money-back guarantee.


woocommerce – How to use $_GET via woocommerce_product_variation_get_price when Woo gets variations by AJAX?

I’m looking to manipulate a variation price using woocommerce_product_variation_get_price

So on the product page when variation calculates the variation price by AJAX, if ?help=1 then the price will change to what I am specifying.

I assume the $_GET['help'] can’t be read by the AJAX getting the variation price.

How can I pass $_GET variables to the AJAX to use in woocommerce_product_variation_get_price?

customization – How do I increase price variations based on multiplication

Please assist by keeping your response basic. I have no coding skills.

I Offer Copiers on my woocommerce website. my intention is to allow product add-ons which i have done using advanced product options. I have two options in terms of pricing. Outright Purchase and Rental. with the building of the product this will ultimately change the total outright price.I would then like to offer the total cost of outright purchase multiplied by 0.02580 which will give a rental figure of R1032.00

I am not looking to pay for plugins.

Thanks in advance