Haskell Hierarchical Libraries (cgi package) Source code Contents Index

Network.CGI.Monad Portability non-portable Stability experimental Maintainer bjorn@bringert.net

Contents CGI monad class CGI monad transformer Error handling

Description

Internal stuff that most people shouldn't have to use. This module mostly deals with the internals of the CGIT monad transformer.

Synopsis

class Monad m => MonadCGI m where cgiAddHeader :: HeaderName -> String -> m () cgiGet :: (CGIRequest -> a) -> m a newtype CGIT m a = CGIT { unCGIT :: (ReaderT CGIRequest (WriterT Headers m) a) } type CGI a = CGIT IO a runCGIT :: Monad m => CGIT m a -> CGIRequest -> m (Headers, a) throwCGI :: (MonadCGI m, MonadIO m) => Exception -> m a catchCGI :: CGI a -> (Exception -> CGI a) -> CGI a tryCGI :: CGI a -> CGI (Either Exception a) handleExceptionCGI :: CGI a -> (Exception -> CGI a) -> CGI a

CGI monad class

class Monad m => MonadCGI m where

The class of CGI monads. Most CGI actions can be run in any monad which is an instance of this class, which means that you can use your own monad transformers to add extra functionality. Methods cgiAddHeader :: HeaderName -> String -> m () Add a response header. cgiGet :: (CGIRequest -> a) -> m a Get something from the CGI request. Instances Monad m => MonadCGI (CGIT m) (MonadTrans t, MonadCGI m, Monad (t m)) => MonadCGI (t m)

CGI monad transformer

newtype CGIT m a

The CGIT monad transformer. Constructors CGIT unCGIT :: (ReaderT CGIRequest (WriterT Headers m) a) Instances MonadTrans CGIT MonadError Exception (CGIT IO) Monad m => Functor (CGIT m) Monad m => Monad (CGIT m) Monad m => MonadCGI (CGIT m) MonadIO m => MonadIO (CGIT m)

type CGI a = CGIT IO a

A simple CGI monad with just IO.

runCGIT :: Monad m => CGIT m a -> CGIRequest -> m (Headers, a)

Run a CGI action.

Error handling

throwCGI :: (MonadCGI m, MonadIO m) => Exception -> m a

Throw an exception in a CGI monad. The monad is required to be a MonadIO, so that we can use throwIO to guarantee ordering.

catchCGI :: CGI a -> (Exception -> CGI a) -> CGI a

Catches any expection thrown by a CGI action, and uses the given exception handler if an exception is thrown.

tryCGI :: CGI a -> CGI (Either Exception a)

Catches any exception thrown by an CGI action, and returns either the exception, or if no exception was raised, the result of the action.

handleExceptionCGI :: CGI a -> (Exception -> CGI a) -> CGI a

Deprecated version of catchCGI. Use catchCGI instead.

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