The combined state and list monad transformer. StateListT σ α is equivalent to StateT σ (ListT α) but more efficient.

WARNING: StateListT σ α m is only a monad if m is a commutative monad. For example,

def problem : StateListT Unit (StateM (Array Nat)) Unit := do
  Alternative.orElse (pure ()) (fun _ => pure ())
  StateListT.lift $ modify (·.push 0)
  StateListT.lift $ modify (·.push 1)

#eval ((problem.run' ()).run #[]).2

will yield either #[0,1,0,1], or #[0,0,1,1], depending on the order in which the actions in the do block are combined.

StateList

inductive Mathlib.Meta.FunProp.StateList (σ α : Type u) : Type u

StateList is a List with a state associated to each element. This is used instead of List (α × σ) as it is more efficient.

• nil {σ α : Type u} : StateList σ α

  .nil is the empty list.

• cons {σ α : Type u} : α → σ → StateList σ α → StateList σ α

  If a : α, s : σ and l : List α, then .cons a s l, is the list with first element a with state s and l as the rest of the list.

instance Mathlib.Meta.FunProp.StateList.instAppend {α σ : Type u} : Append (StateList σ α)

def Mathlib.Meta.FunProp.StateListT (σ : Type u) (m : Type u → Type v) (α : Type u) : Type (max u v)

The combined state and list monad transformer.

@[inline]

def Mathlib.Meta.FunProp.StateListT.run {α σ : Type u} {m : Type u → Type v} [Functor m] (x : StateListT σ m α) (s : σ) : m (List (α × σ))

Run x on a given state s, returning the list of values with corresponding states.

@[inline]

def Mathlib.Meta.FunProp.StateListT.run' {α σ : Type u} {m : Type u → Type v} [Functor m] (x : StateListT σ m α) (s : σ) : m (List α)

Run x on a given state s, returning the list of values.

@[reducible, inline]

abbrev Mathlib.Meta.FunProp.StateListM (σ α : Type u) : Type u

The combined state and list monad.

@[always_inline]

instance Mathlib.Meta.FunProp.StateListT.instMonad {σ : Type u} {m : Type u → Type v} [Monad m] : Monad (StateListT σ m)

instance Mathlib.Meta.FunProp.StateListT.instAlternative {σ : Type u} {m : Type u → Type v} [Monad m] : Alternative (StateListT σ m)

@[inline]

def Mathlib.Meta.FunProp.StateListT.get {σ : Type u} {m : Type u → Type v} [Monad m] : StateListT σ m σ

Return the state from StateListT σ m.

@[inline]

def Mathlib.Meta.FunProp.StateListT.set {σ : Type u} {m : Type u → Type v} [Monad m] : σ → StateListT σ m PUnit

Set the state in StateListT σ m.

@[inline]

def Mathlib.Meta.FunProp.StateListT.modifyGet {α σ : Type u} {m : Type u → Type v} [Monad m] (f : σ → α × σ) : StateListT σ m α

Modify and get the state in StateListT σ m.

@[inline]

def Mathlib.Meta.FunProp.StateListT.lift {α σ : Type u} {m : Type u → Type v} [Monad m] (t : m α) : StateListT σ m α

Lift an action from m α to StateListT σ m α.

instance Mathlib.Meta.FunProp.StateListT.instMonadLift {σ : Type u} {m : Type u → Type v} [Monad m] : MonadLift m (StateListT σ m)

@[always_inline]

instance Mathlib.Meta.FunProp.StateListT.instMonadFunctor {σ : Type u} {m : Type u → Type v} : MonadFunctor m (StateListT σ m)

@[always_inline]

instance Mathlib.Meta.FunProp.StateListT.instMonadExceptOf {σ : Type u} {m : Type u → Type v} [Monad m] {ε : Type u_1} [MonadExceptOf ε m] : MonadExceptOf ε (StateListT σ m)

instance Mathlib.Meta.FunProp.instMonadStateOfStateListT {σ : Type u} {m : Type u → Type v} [Monad m] : MonadStateOf σ (StateListT σ m)

@[always_inline]

instance Mathlib.Meta.FunProp.StateListT.monadControl {σ : Type u} {m : Type u → Type v} [Monad m] : MonadControl m (StateListT σ m)