Questions tagged [parametricity]

Parametricity is the semantic theory of parametrically polymorphic functions, i.e., functions parameterized by type parameters.

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List Functions That Don't Depend on Length

Intuitively, a polymorphic function of type $f : \forall a. [a] \to [a]$ cannot inspect the type of its elements. This intuition can be captured formally using either natural transformations or ...
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How to prove `(∀(M : Monad). ∀a. a → M a) ≅ 𝟙`

Just like the title says, how to prove that equation? The equation basically says that there is only one function a -> M a parametric in both ...
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