instance instToBoolOption {α : Type u_1} : ToBool (Option α)

def OptionT (m : Type u → Type v) (α : Type u) : Type v

Adds the ability to fail to a monad. Unlike ordinary exceptions, there is no way to signal why a failure occurred.

@[inline]

def OptionT.run {m : Type u → Type v} {α : Type u} (x : OptionT m α) : m (Option α)

Executes an action that might fail in the underlying monad m, returning none in case of failure.

@[inline]

def OptionT.mk {m : Type u → Type v} {α : Type u} (x : m (Option α)) : OptionT m α

Converts an action that returns an Option into one that might fail, with none indicating failure.

@[inline]

def OptionT.bind {m : Type u → Type v} [Monad m] {α β : Type u} (x : OptionT m α) (f : α → OptionT m β) : OptionT m β

Sequences two potentially-failing actions. The second action is run only if the first succeeds.

@[inline]

def OptionT.pure {m : Type u → Type v} [Monad m] {α : Type u} (a : α) : OptionT m α

Succeeds with the provided value.

@[always_inline]

instance OptionT.instMonad {m : Type u → Type v} [Monad m] : Monad (OptionT m)

instance OptionT.instInhabitedOfPure {α : Type u} {m : Type u → Type v} [Pure m] : Inhabited (OptionT m α)

@[inline]

def OptionT.orElse {m : Type u → Type v} [Monad m] {α : Type u} (x : OptionT m α) (y : Unit → OptionT m α) : OptionT m α

Recovers from failures. Typically used via the <|> operator.

@[inline]

def OptionT.fail {m : Type u → Type v} [Monad m] {α : Type u} : OptionT m α

A recoverable failure.

instance OptionT.instAlternative {m : Type u → Type v} [Monad m] : Alternative (OptionT m)

@[inline]

def OptionT.lift {m : Type u → Type v} [Monad m] {α : Type u} (x : m α) : OptionT m α

Converts a computation from the underlying monad into one that could fail, even though it does not.

This function is typically implicitly accessed via a MonadLiftT instance as part of automatic lifting.

instance OptionT.instMonadLift {m : Type u → Type v} [Monad m] : MonadLift m (OptionT m)

instance OptionT.instMonadFunctor {m : Type u → Type v} : MonadFunctor m (OptionT m)

@[inline]

def OptionT.tryCatch {m : Type u → Type v} [Monad m] {α : Type u} (x : OptionT m α) (handle : PUnit → OptionT m α) : OptionT m α

Handles failures by treating them as exceptions of type Unit.

instance OptionT.instMonadExceptOfPUnit {m : Type u → Type v} [Monad m] : MonadExceptOf PUnit (OptionT m)

instance OptionT.instMonadExceptOf {m : Type u → Type v} (ε : Type u) [MonadExceptOf ε m] : MonadExceptOf ε (OptionT m)

instance OptionT.instMonadAttach {m : Type u → Type v} [Monad m] [MonadAttach m] : MonadAttach (OptionT m)

instance instMonadControlOptionTOfMonad {m : Type u_1 → Type u_2} [Monad m] : MonadControl m (OptionT m)