WashNGo-2.12: WASH is a family of embedded domain specific languages (EDSL) for programming Web applications in Haskell.ContentsIndex
WASH.CGI.Transaction
Description

Transactional, type-indexed implementation of server-side state.

Glossary

A transactional entity (TE) is a named multi-versioned global variable.

Synopsis
data T a
init :: (Types a, Read a, Show a) => String -> a -> TCGI b (T a)
create :: (Read a, Show a, Types a) => a -> TCGI b (T a)
remove :: Types a => T a -> TCGI b ()
get :: (Read a, Show a) => T a -> TCGI b a
set :: (Read a, Show a) => T a -> a -> TCGI b ()
with :: (WithMonad cgi, Read result, Show result) => result -> (result -> cgi ()) -> (Control (TCGI result) result -> TCGI result ()) -> cgi ()
data Control cgi result = Control {
abandon :: (result -> cgi ())
setFail :: (result -> cgi ())
setCommit :: (result -> cgi ())
}
data TCGI b a
Documentation
data T a
Handle of a transactional variable
show/hide Instances
Read (T a)
Show (T a)
init :: (Types a, Read a, Show a) => String -> a -> TCGI b (T a)
Attempt to create a new tv n and set its initial value. Returns handle to the variable. If the variable already exists, then just returns the handle.
create :: (Read a, Show a, Types a) => a -> TCGI b (T a)
Create a fresh transactional variable with an initial value and return its handle. Performs a physical write to ensure that the variable's name is unique. Locks the transaction directory during the write operation.
remove :: Types a => T a -> TCGI b ()
Remove a transactional variable. Subsequent read accesses to this variable will make the transaction fail. May throw an exception if the variable is not present.
get :: (Read a, Show a) => T a -> TCGI b a
Read transactional variable through a typed handle.
set :: (Read a, Show a) => T a -> a -> TCGI b ()
Write to a transactional variable through typed handle. Only affects the log, no physical write happens. Checks physically for existence of the variable (but tries the log first). Raises exception if it does not exist.
with :: (WithMonad cgi, Read result, Show result) => result -> (result -> cgi ()) -> (Control (TCGI result) result -> TCGI result ()) -> cgi ()
data Control cgi result
Constructors
Control
abandon :: (result -> cgi ())abandon with result (rollback)
setFail :: (result -> cgi ())set result on failure
setCommit :: (result -> cgi ())set result on successful commit
data TCGI b a
Type of a CGI action in a transactional scope with a result variable of type a.
show/hide Instances
CGIMonad (TCGI b)
Monad (TCGI b)
WithMonad (TCGI x)
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