28 lines
992 B
Text
28 lines
992 B
Text
/-
|
||
Copyright (c) Luke Nelson and Jared Roesch. All rights reserved.
|
||
Released under Apache 2.0 license as described in the file LICENSE.
|
||
Authors: Leonardo de Moura, Luke Nelson, Jared Roesch, Sebastian Ullrich
|
||
-/
|
||
prelude
|
||
import init.control.applicative
|
||
universes u v
|
||
|
||
open Function
|
||
|
||
class HasBind (m : Type u → Type v) :=
|
||
(bind : Π {α β : Type u}, m α → (α → m β) → m β)
|
||
|
||
export HasBind (bind)
|
||
|
||
infixl ` >>= `:55 := bind
|
||
|
||
class Monad (m : Type u → Type v) extends Applicative m, HasBind m : Type (max (u+1) v) :=
|
||
(map := λ α β f x, x >>= pure ∘ f)
|
||
(Seq := λ α β f x, f >>= (<$> x))
|
||
(seqLeft := λ α β x y, x >>= λ a, y >>= λ _, pure a)
|
||
(seqRight := λ α β x y, x >>= λ _, y)
|
||
|
||
/- We do not add this instance by default because it is rarely needed,
|
||
and it could slow down the current type class resolution procedure. -/
|
||
def monadInhabited {α : Type u} {m : Type u → Type v} [Monad m] [Inhabited α] : Inhabited (m α) :=
|
||
⟨pure $ default _⟩
|