- saveState : m s
- restoreState : s → m Unit
Similar to MonadState, but it retrieves/restores only the "backtrackable" part of the state
Instances
def
Lean.commitWhenSome?
{m : Type → Type}
{s : Type}
{ε : Type u_1}
{α : Type}
[inst : Monad m]
[inst : Lean.MonadBacktrack s m]
[inst : MonadExcept ε m]
(x? : m (Option α))
:
m (Option α)
Execute x?, but backtrack state if result is none or an exception was thrown.
Equations
- One or more equations did not get rendered due to their size.
def
Lean.commitWhenSomeNoEx?
{m : Type → Type}
{s : Type}
{ε : Type u_1}
{α : Type}
[inst : Monad m]
[inst : Lean.MonadBacktrack s m]
[inst : MonadExcept ε m]
(x? : m (Option α))
:
m (Option α)
Execute x?, but backtrack state if result is none or an exception was thrown.
If an exception is thrown, none is returned.
That is, this function is similar to commitWhenSome?, but swallows the exception and returns none.
Equations
- One or more equations did not get rendered due to their size.
def
Lean.commitWhen
{m : Type → Type}
{s : Type}
{ε : Type u_1}
[inst : Monad m]
[inst : Lean.MonadBacktrack s m]
[inst : MonadExcept ε m]
(x : m Bool)
:
m Bool
Equations
- One or more equations did not get rendered due to their size.
def
Lean.commitIfNoEx
{m : Type → Type}
{s : Type}
{ε : Type u_1}
{α : Type}
[inst : Monad m]
[inst : Lean.MonadBacktrack s m]
[inst : MonadExcept ε m]
(x : m α)
:
m α
Equations
- Lean.commitIfNoEx x = do let s ← Lean.saveState tryCatch x fun ex => do Lean.restoreState s throw ex
def
Lean.withoutModifyingState
{m : Type → Type}
{s : Type}
{α : Type}
[inst : Monad m]
[inst : MonadFinally m]
[inst : Lean.MonadBacktrack s m]
(x : m α)
:
m α
Equations
- Lean.withoutModifyingState x = do let s ← Lean.saveState tryFinally x (Lean.restoreState s)
def
Lean.observing?
{m : Type → Type}
{s : Type}
{ε : Type u_1}
{α : Type}
[inst : Monad m]
[inst : Lean.MonadBacktrack s m]
[inst : MonadExcept ε m]
(x : m α)
:
m (Option α)
Equations
- One or more equations did not get rendered due to their size.
instance
Lean.instMonadBacktrackExceptT
{s : Type}
{m : Type → Type}
{ε : Type}
[inst : Lean.MonadBacktrack s m]
[inst : Monad m]
:
Lean.MonadBacktrack s (ExceptT ε m)
Equations
- Lean.instMonadBacktrackExceptT = { saveState := ExceptT.lift Lean.saveState, restoreState := fun s => ExceptT.lift (Lean.restoreState s) }