Library for handling global entities.
A global entity has a name declared in the program.
Its value can be accessed and modified by IO actions.
Furthermore, global entities can be declared as persistent so that
their values are stored across different program executions.
Currently, it is still experimental so that its interface might
be slightly changed in the future.
A global entity g with an initial value v
of type t must be declared by:
g :: Global t
g = global v spec
Here, the type t must not contain type variables and
spec specifies the storage mechanism for the
global entity (see type GlobalSpec).
Author: Michael Hanus
Version: June 2007
| Exported names: |
Datatypes:
Global
| GlobalSpec
Constructors:
Persistent
| Temporary
Functions:
global
| readGlobal
| writeGlobal
| Summary of exported functions: |
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| Imported modules: |
| Exported datatypes: |
The general type of dynamic predicates.
Constructors:
The storage mechanism for the global entity.
Constructors:
:: GlobalSpec
Temporary - the global value exists only during a single execution
of a program
:: String -> GlobalSpec
Persistent f - the global value is stored persisently in file f
(which is created and initialized if it does not exists)
| Exported functions: |
:: a -> GlobalSpec -> Global a 
global is only used for the declaration of a global value
and should not be used elsewhere. In the future, it might become a keyword.
:: Global a -> IO a
Reads the current value of a global.
:: Global a -> a -> IO ()
Updates the value of a global. The value is evaluated to a ground constructor term before it is updated.