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// nestedTree is a tree structure containing subtrees under "nodes" property. d=1 is the default "depth of the tree"
function flatDeep(arr, d = 1) {
    return d > 0 ? arr.reduce((acc, val) => acc.concat(Array.isArray(val.nodes) ? flatDeep(val.nodes, d - 1) : val), [])
                 : arr.slice();
 };

let flat = flatDeep(nestedTree, Infinity);
// Source: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat

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const idMapping = data.reduce((acc, el, i) => {
    acc[el.id] = i;
    return acc;
}, {});

let root = [];
data.forEach(el => {
    // Handle the root element
    if (el.parent === null) {
        root.push(el);

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#!/bin/bash

sudo /usr/local/bin/certbot-auto renew
sudo cp /etc/letsencrypt/live/domain.com/* /etc/lighttpd/certs/
cd /etc/lighttpd/certs
sudo cat privkey.pem cert.pem | sudo tee merged.pem

sudo systemctl restart lighttpd.service

## Renew every two months

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#!/bin/bash

# delete previous version if needed
INSTALL_DIR=/usr/share/code
if [ -d "$INSTALL_DIR" ]; then
        echo "deleting: $INSTALL_DIR"
        sudo rm -rf $INSTALL_DIR
fi

# download the rpm from https://code.visualstudio.com/download

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On the computer without public IP:

ssh -R 2222:localhost:22 loginOfServerWithPublicIP@publicIP

This connects to the server by SSH and builds a tunnel from the server with public IP on port 2222 to the computer without public IP on port 22 (SSH).

And then on the server:

ssh -p 2222 loginOfComputerWithoutPublicIP@locahost

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function long {
    START=$(date +%s.%N)
    $*
    EXIT_CODE=$?
    END=$(date +%s.%N)
    DIFF=$(echo "$END - $START" | bc)
    RES=$(python -c "diff = $DIFF; min = int(diff / 60); print('%s min' % min)")
    result="$1 completed in $RES, exit code $EXIT_CODE."
    echo -e "\n⏰  $result"
    ( say -r 250 $result 2>&1 > /dev/null & )

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#include <stdio.h>
 
typedef void (*functionType)();

void doThis() {
    printf("Hello World!\n");
}

int main() {
    functionType doVar = &doThis;

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#include <stdio.h>
void printNumber(int nbr)  
{
    printf("%d\n", nbr);
}
void myFunction(void (*f)(int))  
{
    for(int i = 0; i < 5; i++) 
    {
        (*f)(i);

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Change python version system-wide

To change python version system-wide we can use update-alternatives command. Logged in as a root user, first list all available python alternatives:

# update-alternatives --list python
update-alternatives: error: no alternatives for python

The above error message means that no python alternatives has been recognized by update-alternatives command. For this reason we need to update our alternatives table and include both python2.7 and python3.4:

# update-alternatives --install /usr/bin/python python /usr/bin/python2.7 1
update-alternatives: using /usr/bin/python2.7 to provide /usr/bin/python (python) in auto mode

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Flip last two edges in place. Front-top edge and left-top edge.

For this example, an algorithm that is more simple to remember, 
and can be altered for the other case (opposite edges), is this: 
F' E F2 E2 F' U' F E2 F2 E' F and U. 

Replace U and U' with U2 for the case of flipping two opposite edges on top face.
(E is the equatorial slice, viewed from face U)