38 lines
967 B
Text
38 lines
967 B
Text
/-
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Copyright (c) 2016 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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-/
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prelude
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import init.category.functor
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import init.function
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open function
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universes u v
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class applicative (f : Type u → Type v) extends functor f : Type (max u+1 v):=
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(pure : Π {a : Type u}, a → f a)
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(seq : Π {a b : Type u}, f (a → b) → f a → f b)
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section
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variables {a b : Type u} {f : Type u → Type v} [applicative f]
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@[inline] def pure : a → f a :=
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applicative.pure f
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@[inline] def seq_app : f (a → b) → f a → f b :=
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applicative.seq
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infixl ` <*> `:2 := seq_app
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/-- Sequence actions, discarding the first value. -/
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def seq_left (x : f a) (y : f b) : f a :=
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pure (λ x y, x) <*> x <*> y
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/-- Sequence actions, discarding the second value. -/
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def seq_right (x : f a) (y : f b) : f b :=
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pure (λ x y, y) <*> x <*> y
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infixl ` <* `:2 := seq_left
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infixl ` *> `:2 := seq_right
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end
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