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Comments on Determine whether an integer is square-free

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Determine whether an integer is square-free

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An integer is called square-free if it is not a multiple of a perfect square other than 1. For example, 42 is square-free, but 44 is not because it is a multiple of the perfect square 4 = 2².

Your task is to write a program or function that takes a positive integer, and returns a truthy value if the integer is square-free and a falsey value otherwise.

This is code golf, the shortest code wins.

The square-free numbers are OEIS sequence A005117 (thanks to Razetime for pointing this out).

Some test cases:

  1  true
  2  true
  3  true
  4  false
  5  true
  6  true
  7  true
  8  false
  9  false
 10  true
 12  false
 14  true
 16  false
 18  false
 20  false
 30  true
 40  false
 50  false
100  false
110  true
111  true
code-golf number-theory
posted almost 3 years ago
3y ago
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celtschk‭
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2 comment threads

Testcases? (2 comments)
[relevant oeis](http://oeis.org/A005117) (2 comments)
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+1
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Myby, 12 5 bytes

primf=primfd

primf        : prime factors
     =       : equals
      primfd : unique prime factors

Evaluated as a monadic fork in J (f y) g (h y).

The test cases (retested) can be viewed here and were generated using this ruby script.

posted over 2 years ago
2y ago
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south‭
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1 comment thread

How is this 5 bytes? I count 12 letters, each of which requires one byte. (2 comments)
How is this 5 bytes? I count 12 letters, each of which requires one byte.
celtschk‭ wrote over 2 years ago
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How is this 5 bytes?

I count 12 letters, each of which requires one byte.

Conor O'Brien‭ wrote over 2 years ago
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Myby uses a "Literate Mode" to write and communicate programs. However, programs are scored by the bytes used by the interpreter, which are not (as) human readable. In this case, the program primf=primfd corresponds to the 5 bytes (written here by the corresponding hex) FE 72 F4 FE 74. FE72 corresponds to primf, F4 corresponds to =, and FE74 corresponds to primfd. Naturally, it is much more informative to share the Literate Mode as opposed to the actual bytes, which are, in this case, entirely printable as þrôþt, but often contain unprintable characters. Furthermore, since Myby programs bestow meaning to individual NIbbles (half-bytes), such a representation does not come close to reasonably representing the program's behavior. You can read more about the language here: https://github.com/ConorOBrien-Foxx/Myby