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Comments on Make my number a set

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Make my number a set

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Natural to set

(set meaning an unordered collection with no duplicates, though answers may use and output lists instead)

Recently I was brainstorming what a language with only (arbitrarily nested) sets would be like. A number is represented with a set of that many elements. The elements need to be different, which leads to this definition:

Definition

  • The set representation of $0$ is the empty set.
  • The set representation of any other integer $n$ is the set of the set representations of all positive integers less than $n$, including zero.
  • Negative, complex, or rational numbers do not need to be handled.
  • Your full program or function is to convert from a positive integer to a set or list.

Examples

0 {}
1 {{}}
2 {{}, {{}}}
3 {{}, {{}}, {{}, {{}}}}
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JavaScript (V8), 32 bytes

f=n=>[...Array(n).keys()].map(f)

Try it online!

Somehow it doesn't recurse forever at n=0. Pretty nice.

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Wezl‭ wrote over 3 years ago

It doesn't recurse forever because Array(0) = [], and .keys() and .map(f) don't do anything for empty lists