| Safe Haskell | Trustworthy |
|---|---|
| Language | Haskell2010 |
Control.Monad.Chronicle.Class
Description
Hybrid error/writer monad class that allows both accumulating outputs and aborting computation with a final output.
The expected use case is for computations with a notion of fatal vs. non-fatal errors.
Documentation
class Monad m => MonadChronicle c m | m -> c where Source #
Methods
disclose :: Default a => c -> m a Source #
disclose cc and returns a
Default
This is a convenience function for reporting non-fatal errors in one
branch a case, or similar scenarios when there is no meaningful
result but a placeholder of sorts is needed in order to continue.
confess cc.
Equivalent to throwError for the Error monad.
memento :: m a -> m (Either c a) Source #
memento mm, returning either
its record if it ended with confess, or its final value otherwise, with
any record added to the current record.
Similar to catchError in the Error monad, but with a notion of
non-fatal errors (which are accumulated) vs. fatal errors (which are caught
without accumulating).
absolve :: a -> m a -> m a Source #
absolve x mm and discards any
record it had. The default value x will be used if m ended via
confess.
condemn :: m a -> m a Source #
condemn mm and keeps its value
only if it had no record. Otherwise, the value (if any) will be discarded
and only the record kept.
This can be seen as converting non-fatal errors into fatal ones.
retcon :: (c -> c) -> m a -> m a Source #
retcon f mm and applies the
function f to its output, leaving the return value unchanged.
chronicle :: These c a -> m a Source #
chronicle mThese c aMonadChronicle instance.