Middle Dot (·)

·: Nothing

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Indicates no value. If a left argument is Nothing, the function is called with no left argument, and if the right is Nothing, it's not called and "returns" Nothing.

    · ⌽ "abc"  # Reverse instead of Rotate
"cba"

In Trains

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Nothing can serve as a left argument in a train to string together multiple monadic functions.

    (-+-) 5
¯10

    (-·+-) 5
5

Destructuring

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For pattern matching in assignment or a block header, Nothing indicates an unused value.

    F ← {𝕊 a‿·‿b: a∾b}

    F 1‿2‿3
⟨ 1 3 ⟩