Safe Haskell  Trustworthy 

Language  Haskell2010 
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. nonfatal errors.
Synopsis
 type Chronicle c = ChronicleT c Identity
 chronicle :: Monad m => These c a > ChronicleT c m a
 runChronicle :: Chronicle c a > These c a
 newtype ChronicleT c m a = ChronicleT {
 runChronicleT :: m (These c a)
 dictate :: (Semigroup c, Monad m) => c > ChronicleT c m ()
 disclose :: (Default a, Semigroup c, Monad m) => c > ChronicleT c m a
 confess :: (Semigroup c, Monad m) => c > ChronicleT c m a
 memento :: (Semigroup c, Monad m) => ChronicleT c m a > ChronicleT c m (Either c a)
 absolve :: (Semigroup c, Monad m) => a > ChronicleT c m a > ChronicleT c m a
 condemn :: (Semigroup c, Monad m) => ChronicleT c m a > ChronicleT c m a
 retcon :: (Semigroup c, Monad m) => (c > c) > ChronicleT c m a > ChronicleT c m a
The Chronicle monad
type Chronicle c = ChronicleT c Identity Source #
runChronicle :: Chronicle c a > These c a Source #
The ChronicleT monad transformer
newtype ChronicleT c m a Source #
The ChronicleT
monad transformer.
The return
function produces a computation with no output, and >>=
combines multiple outputs with <>
.
ChronicleT  

Instances
Chronicle operations
confess :: (Semigroup c, Monad m) => c > ChronicleT c m a Source #
is an action that ends with a final output confess
cc
.
Equivalent to throwError
for the Error
monad.
memento :: (Semigroup c, Monad m) => ChronicleT c m a > ChronicleT c m (Either c a) Source #
is an action that executes the action 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
nonfatal errors (which are accumulated) vs. fatal errors (which are caught
without accumulating).
absolve :: (Semigroup c, Monad m) => a > ChronicleT c m a > ChronicleT c m a Source #
condemn :: (Semigroup c, Monad m) => ChronicleT c m a > ChronicleT c m a Source #
is an action that executes the action 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 nonfatal errors into fatal ones.
retcon :: (Semigroup c, Monad m) => (c > c) > ChronicleT c m a > ChronicleT c m a Source #