11 lines
260 B
Text
11 lines
260 B
Text
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--| Retrieve the first element of the list
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let head
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: ∀(a : Type) → List a → Optional a
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= List/head
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let example0 = assert : head Natural [ 0, 1, 2 ] ≡ Some 0
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let example1 = assert : head Natural ([] : List Natural) ≡ None Natural
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in head
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