## Difference in formulas for the combination

Can someone please tell me what the difference is $$binom {n + k-1} {k-1}$$ and $$binom {n-1} {k-1}$$?

## What is the difference between / and // in terminal commands?

As you go through the terminal, simply change the directory with / and // and the same contents of the root directory will be displayed. What is the difference between the two?

## set the difference between two non-regular languages

Let's say we have $$L_1$$ and $$L_2$$ two non-regular languages. is $$L_1$$ $$L_2$$ is not always regular languages?

## What is the difference between a focal plane shutter and a wing shutter of a camera?

The biggest difference in function between a blade shutter and a slit shutter is the ability of a slit shutter to allow exactly the same exposure time for the entire light field collected at the front of the lens and practical use to allow faster shutter speeds.

Due to the fact that the shutters are opened longer in the middle than at the edges, the light that falls through the center of the lens falls slightly longer on the image plane than the light that comes from the edges of the lens. This was not such a big issue at the beginning of the photograph, and the emulsions were so low in sensitivity that the typical exposure times were in minutes rather than hundredths or thousandths of a second! In fact, the first "shutters" were lens caps or plugs that were manually removed and replaced on the front of the lens.

As cameras became more photosensitive and the desired exposure times became shorter and shorter, the limitations of the blade shutter became a more important problem. Nevertheless, today there are still new digital cameras that work with shutters. The designers agree and the market seems to agree that the compromises are worthwhile in some cases.

A slit shutter can be designed to start exposure on one side of the frame and terminate on the other side of the frame. In this way, all parts of the frame can receive light from all parts of the lens for the same time. The earliest single curtain shutters, as used in the speed graph, had a fixed slot that ran through the focal plane. By allowing the user to select different slot widths and spring loads for the mechanism that moved the slot across the focal plane, shutter speeds in the range of 1/10 second to 1/1000 second were possible with most different models of the Speed ​​Graphic.

Why should the Speed ​​Graphic have both a focal plane and a blade shutter? That does not have to be need a shutter. Tubular lenses without wing lock can be used with a Speed ​​Graphic. The slot shutter is used for speedIn particular, shorter shutter speeds, so the name speed graphics, But it certainly was not the camera fast Regarding the shot-to-shot intervals and the operation of the FP shutter, manually resetting the FP curtain between shots took longer than operating a shutter in the lens. This may be one reason why many users prefer both options. The lens-sealed lenses offered by the lens manufacturers can be used on both the Speed ​​Graphic, Crown Graphic and Century Graphic models. (The lack of a focal plane shutter made it possible to thin the Crown Graphic a bit, allowing it to use some wide-angle lenses faster than the Speed ​​Graphic did.)

Although this is not exactly true for your particular model, here is a link to the instructions for a top speed graph of about 1925.

## Bitcoin Core – difference between inbound and outbound connection

I use a Bitcoin full node (Bitcoin kernel) over Tor.
I noticed that I only have outgoing connections (with maxconnections = 16 in the conf file), but not even an incoming one.
So what exactly is the difference between inbound and outbound?

## Calculate the height difference with CSS

Is there a way for me to do that? code below that is in JQuerybut with CSS?

`````` \$(document).scroll(function() {

if (  \$(this).scrollTop() > \$(window).height() ) {

\$("section#topo").css("height", 50);
\$("section#topo").css("background", "#999");

} else {

\$("section#topo").css("height", 80);
\$("section#topo").css("background", "none");

}

});
``````

The idea would be something like:

``````
calc (body.scrollTop > window.height) {
section#topo {
height: 50;
background: #999;
}
}

calc (body.scrollTop <= window.height) {
section#topo {
height: 80;
background: none;
}
}

``````

## script – What does the Bitcoin policy language offer the developer, which Miniscript does not offer? What is the difference between the Bitcoin policy language and Miniscript?

On a high level:

• The policy is compiled to Minsicript.
• Miniscript is coded to Bitcoin Script. (One to one assignment)
• Bitcoin script is decrypts back to the miniscript. (One to one assignment)
• Policy and miniscript can both Be canceled to another presentation
for static analysis.

The following invariants are considered in Miniscript:
To let `ms` be a mini script, `s` be bitcoin script, `pol` Be politics

• `decode(encode(ms))` = `ms`
• `encode(decode(s))` = `s`
• `lift(pol)` = `lift(compile(pol))`

I do not go into the details of lifting, as it is not directly related to the question.

When would I use the policy language instead of miniscript? What does the policy language offer that Miniscript does not offer? What are the main differences between them?

I think this question is best answered with an example.

Writing an efficient miniscipt directly from the issue conditions is not trivial. Political language is a more natural way of writing output conditions. Consider a hashlock example from Bob to Alice, your requirements are

• Alice can spend the coins if she knows a model for Hash H.
• The money will be returned to Bob after some time. Let's say 10 blocks

Of course this leads to the following guidelines
`or(and(sha256(H),pk(A)),and(older(10),pk(B)))` , Writing a mini script directly would be complicated and would probably prove inefficient. Here the compiler can help you.

The compiler then compiles a miniscript like the one shown below.
`andor(c:pk(A),sha256(H),and_v(vc:pk(B),older(10)))` that has a one to one assignment to script.

Note that it is not trivial to write down this miniscript directly and to write complicated fragments like `andor`,

In addition, the policy language allows you to indicate the odds of winning (by using `@` as shown below) for a `or` Branching that can help the compiler create a vbyte-efficient script. In the above example, we expect the hashlock to be very likely to succeed, and the timelock branch should almost never be used. We can use the odds in the policy language as follows:

`or(99@and(sha256(H),pk(A)),1@and(older(10),pk(B)))`

which is then compiled into another miniscript (note that `pk(B)` changed to `pk_h(B)`)

`andor(c:pk(A),sha256(H),and_v(vc:pk_h(B),older(10)))`

## list peers

`listpeers` Returns data to nodes to which you are connected OR to the nodes with which you have an open channel. If you have opened a channel with a node but the connection to that node has been lost, the node is still displayed in the output `"connected": false`, If you are connected to a node but have no open channels, the output will be returned with `"channels": []`,

If you want to get information about a specific peer, not all, you can add the node ID of the peer as follows: `lightning-cli listpeers `, You can also query log entries related to the peer by passing the command: `lightning-cli listpeers ` where can be `io`. `debug`. `info`, and `unusual`, Log levels can only be queried if a node ID is specified.

## nodes list

`listnodes` returns the information of all nodes in your local network view. This information is collected through the Klatschnetz. If you are the `listnodes` If you run the command without a node ID, the RPC returns the information of ALL nodes in your view. If you are interested in the information of a particular node ID, you can do so by passing the command: `lightning-cli listnodes `,

## What is the difference between object and value in Python?

I tried to find that answer, but I could not find the right explanation

Some say they are the same and others say something different

I know for a composite object, the object will consist of several values

But for simple objects like int or string we can say that they are identical and values ​​themselves are objects?

thanks