class type['a]cache_t =object..end
A cache contains a mutable value that is obtained by running an engine.
method get_engine : unit -> 'a engineRequests the value. If it is not already in the cache, the engine for getting the value is started, and it is waited until the value is available.
method get_opt : unit -> 'a optionReturns the cached value if available
method put : 'a -> unitPuts a value immediately into the cache. It replaces an existing
value. If it is currently tried to obtain a new value by running
an engine, this engine is kept running, and get_engine will
return its result. Only future calls of get_engine will return
the value just put into the cache.
method invalidate : unit -> unitInvalidates the cache - if a value exists in the cache, it is removed.
If in the future the cache value is requested via get_engine
the engine will be started anew to get the value.
Note that (as for put) any already running get_engine is not
interrupted.
method abort : unit -> unitAny engine running to get the cache value is aborted, and the contents
of the cache are invalidated. Note that also the engines returned
by get_engine are aborted.
