A header-only C implementation of C++ <algorithm>

In practice, the biggest traits of communisms were (of the top of my head, I might be missing something):

1. No private property of the wealth-generating kind. The land, the companies - they can only be owned by the state.

2. No families. The whole country is one big commune, and there's no reason for a mother to favor her own child over some stranger in Novosibirsk 5000 miles from her. (This was too radical though - it turned out that even the greatest opression and terror cannot break the familial ties. The communists abandoned this idea within a dozen or so years of them seizing power).

3. No faith. Churches were demolished or turned into grain stores etc. The clergy was persecuted.

4. Independent thought is forbidden and can easily get you killed - either by shot in the head somewhere in the basement in e.g. NKWD HQ in Moscow, or in one of hundreds of Gulags across the Soviet Union.

5. A corollary to the above - any independent action is highly suspicious. If you and two neighbors start tending to the local garden together, it's already suspicious, because you're starting an "organization" - and all forms of organizing are strictly controlled and must be introduced in a top-down manner. The reason behind this is of course to keep people extremely atomized, so that they're powerless against the state and will never rebel.

5. The country is a police state. Czeka, later rebranded as NKWD, and later rebranded as KGB (the constant rebrandings were due to atrocities that those people were constantly committing) is the most powerful organization in the state. They have informers everywhere, likely among your family, and most likely among your colleagues at work or school.

6. Traditions are dangerous and must be destroyed. Soviet Union displaced many of its nations (yes, entire nations) within its borders, to uproot them and weaken them. Once people's ties with the land were gone, it was easier to make them into obedient workers in state's companies.

7. The state used people as fuel. Esp. during the 1920-1945 period, Russia had more people than other resources, so the authorities turned milions of people into slaves, who worked without compensation on their great industrial projects across the Gulag (building river canals in the arctic regions, building railways through Siberia, mining uranium in -60 degrees weather etc). To save money and accelerate the country's growth, the slaves were malnourished by design, receiving less than 50% of calories they need. This resulted in them slowly buring their own tissues, which resulted in grown men weighing as little as 80 pounds after a couple years of slave work. This was extremely similar to Auschwitz and other German concentration camps, with the exception that Soviet authorities were predominantly doing this to their own people.

8. Terror. During periods of intensified terror (which could last years), no one was safe. You could be arrested at any point under most frivolous pretense (e.g. not clapping long enough after a speech of a political leader), and many millions were. The arrest would most likely lead to you ending up in Gulag as a slave and fuel for the industrial machine. What's worse, your family, petrified with fear over their own lives, would distance from you - e.g. wives often denounced their arrested husbands, and broke all contact. Even if you survived the Gulags and your "sentence" was carried out and you were finally free, you were often still a pariah. Your biggest hope was for the current leader of the country to die, and the next one declare him an abuser, which in practice led to an official pardon of people sent go Gulag under the previous regime.

9. The totalitarian aspect of the state and its ideology. Every aspect of life had to either originate from the state or at least be mediated by it. It's still present in e.g. North Korea, where a grown person is allowed to go to work, go to the store, go the local party meetup (daily meetups after work are often mandatory), perhaps go to its immediate family - and that's it. If you go (as in, physical movement on the street) anywhere else, it's suspcious, and the police can stop and question you.

The totalitarian aspect was also prevalent in intellectual life - if you were working on something that the state deemed politically benign and was hence permitted - let's say you were a university professor writing a biography of Michelangelo - you still had to write it through the lens of Marxism, or you'd be in trouble. Marxism had to explain events in Michelangelo's life, as well as the society around him.

BTW, it's a great shame that this is not widely known across the Western world. This would motivate people to avoid the horrors that could be unleashed if we go to far towards the leftist utopian (in reality, dystopian) ideas. Unfortunately, the Western intellectual elites have decades of tradition of downplaying that, and being in favor radical leftism. Let's hope we won't see people Gulags in the US in XXI century.