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BQN, 17 bytesSBCS {𝕩∾1𝕊⍟≠⌊𝕩⋆2|𝕩+÷2} Run online! BQN primitives alone can't express unbounded iteration, so this must be a recursive block function. {𝕩∾1𝕊⍟≠⌊𝕩⋆2|𝕩+÷2} # Function 𝕊 taking argu...

posted 5y ago by Marshall Lochbaum‭

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#1: Initial revision by

Marshall Lochbaum‭ · 2021-05-05T02:12:06Z (over 5 years ago)

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# [BQN](https://mlochbaum.github.io/BQN/), 17 bytes<sup>[SBCS](https://github.com/mlochbaum/BQN/blob/master/commentary/sbcs.bqn)</sup>

```
{𝕩∾1𝕊⍟≠⌊𝕩⋆2|𝕩+÷2}
```

[Run online!](https://mlochbaum.github.io/BQN/try.html#code=SlPihpB78J2VqeKIvjHwnZWK4o2f4omg4oyK8J2VqeKLhjJ88J2VqSvDtzJ9CgriiY3LmOKfnChKU8KoKSAyK+KGlTk=)

BQN primitives alone can't express unbounded iteration, so this must be a recursive [block](https://mlochbaum.github.io/BQN/doc/block.html) function.

```
{𝕩∾1𝕊⍟≠⌊𝕩⋆2|𝕩+÷2}  # Function 𝕊 taking argument 𝕩
              ÷2   # Reciprocal of 2 (one half)
            𝕩+     # Plus 𝕩
          2|       # Modulo 2
        𝕩⋆         # 𝕩 power
       ⌊           # Floor
    𝕊              # Keep going
   1 ⍟≠            # ...if not 1
 𝕩∾                # Prepend 𝕩
```

`1𝕊⍟≠…` passes 1 as the left argument `𝕨`, which is harmless.

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