24 lines
766 B
Text
24 lines
766 B
Text
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--| Transform the value with a function and flatten the resulting `Optional`
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let concatMap
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: ∀(a : Type) → ∀(b : Type) → (a → Optional b) → Optional a → Optional b
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= λ(a : Type) →
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λ(b : Type) →
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λ(f : a → Optional b) →
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λ(o : Optional a) →
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merge { Some = f, None = None b } o
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let exampleFun
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: Natural → Optional Natural
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= λ(n : Natural) → if Natural/even n then Some (n + 1) else None Natural
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let example0 =
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assert : concatMap Natural Natural exampleFun (Some 1) ≡ None Natural
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let example1 = assert : concatMap Natural Natural exampleFun (Some 2) ≡ Some 3
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let example2 =
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assert
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: concatMap Natural Natural exampleFun (None Natural) ≡ None Natural
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in concatMap
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