Pipes.Lift

Many actions in base monad transformers cannot be automatically lifted. These functions lift these remaining actions so that they work in the Proxy monad transformer.

ErrorT

errorP :: (Monad m, Error e) => Proxy a' a b' b m (Either e r) -> Proxy a' a b' b (ErrorT e m) r

Wrap the base monad in ErrorT

runErrorP :: (Monad m, Error e) => Proxy a' a b' b (ErrorT e m) r -> Proxy a' a b' b m (Either e r)

Run ErrorT in the base monad

catchError

Arguments

:: (Monad m, Error e)

=> Proxy a' a b' b (ErrorT e m) r

-> (e -> Proxy a' a b' b (ErrorT e m) r)

-> Proxy a' a b' b (ErrorT e m) r

Catch an error in the base monad

liftCatchError

Arguments

:: Monad m

=> (m (Proxy a' a b' b m r) -> (e -> m (Proxy a' a b' b m r)) -> m (Proxy a' a b' b m r))

-> Proxy a' a b' b m r -> (e -> Proxy a' a b' b m r) -> Proxy a' a b' b m r

Catch an error using a catch function for the base monad

MaybeT

maybeP :: Monad m => Proxy a' a b' b m (Maybe r) -> Proxy a' a b' b (MaybeT m) r

Wrap the base monad in MaybeT

runMaybeP :: Monad m => Proxy a' a b' b (MaybeT m) r -> Proxy a' a b' b m (Maybe r)

Run MaybeT in the base monad

ReaderT

readerP :: Monad m => (i -> Proxy a' a b' b m r) -> Proxy a' a b' b (ReaderT i m) r

Wrap the base monad in ReaderT

runReaderP :: Monad m => i -> Proxy a' a b' b (ReaderT i m) r -> Proxy a' a b' b m r

Run ReaderT in the base monad

StateT

stateP :: Monad m => (s -> Proxy a' a b' b m (r, s)) -> Proxy a' a b' b (StateT s m) r

Wrap the base monad in StateT

runStateP :: Monad m => s -> Proxy a' a b' b (StateT s m) r -> Proxy a' a b' b m (r, s)

Run StateT in the base monad

evalStateP :: Monad m => s -> Proxy a' a b' b (StateT s m) r -> Proxy a' a b' b m r

Evaluate StateT in the base monad

execStateP :: Monad m => s -> Proxy a' a b' b (StateT s m) r -> Proxy a' a b' b m s

Execute StateT in the base monad

WriterT

Note that runWriterP and execWriterP will keep the accumulator in weak-head-normal form so that folds run in constant space when possible.

This means that until transformers adds a truly strict WriterT, you should consider unwrapping WriterT first using runWriterP or execWriterP before running your Proxy. You will get better performance this way and eliminate space leaks if your accumulator doesn't have any lazy fields.

writerP :: (Monad m, Monoid w) => Proxy a' a b' b m (r, w) -> Proxy a' a b' b (WriterT w m) r

Wrap the base monad in WriterT

runWriterP :: (Monad m, Monoid w) => Proxy a' a b' b (WriterT w m) r -> Proxy a' a b' b m (r, w)

Run WriterT in the base monad

execWriterP :: (Monad m, Monoid w) => Proxy a' a b' b (WriterT w m) r -> Proxy a' a b' b m w

Execute WriterT in the base monad

RWST

rwsP :: (Monad m, Monoid w) => (i -> s -> Proxy a' a b' b m (r, s, w)) -> Proxy a' a b' b (RWST i w s m) r

Wrap the base monad in RWST

runRWSP :: (Monad m, Monoid w) => r -> s -> Proxy a' a b' b (RWST r w s m) d -> Proxy a' a b' b m (d, s, w)

Run RWST in the base monad

evalRWSP :: (Monad m, Monoid w) => r -> s -> Proxy a' a b' b (RWST r w s m) d -> Proxy a' a b' b m (d, w)

Evaluate RWST in the base monad

execRWSP :: (Monad m, Monoid w) => r -> s -> Proxy a' a b' b (RWST r w s m) d -> Proxy a' a b' b m (s, w)

Execute RWST in the base monad

Utilities

distribute

Arguments

:: (Monad m, MonadTrans t, MFunctor t, Monad (t m), Monad (t (Proxy a' a b' b m)))

=> Proxy a' a b' b (t m) r

-> t (Proxy a' a b' b m) r

Distribute Proxy over a monad transformer