Relations Between The Expressiveness of Different Forms of Future
Eager thread-specific futures can be straightforwardly implemented in terms of non-thread-specific futures, by creating a thread to calculate the value at the same time as creating the future. In this case it is desirable to return a read-only view to the client, so that only the newly created thread is able to resolve this future.
To implement implicit lazy thread-specific futures (as provided by Alice ML, for example) in terms in non-thread-specific futures, needs a mechanism to determine when the future's value is first needed (for example, the WaitNeeded construct in Oz). If all values are objects, then the ability to implement transparent forwarding objects is sufficient, since the first message sent to the forwarder indicates that the future's value is needed.
Non-thread-specific futures can be implemented in terms of thread-specific futures, assuming that the system supports message passing, by having the resolving thread send a message to the future's own thread. However, this could be argued to be unnecessary complexity: in programming languages based on threads, the most expressive approach appears to be to provide a combination of non-thread-specific futures, read-only views, and either a 'WaitNeeded' construct or support for transparent forwarding.
Read more about this topic: Futures And Promises
Famous quotes containing the words relations between, relations, forms and/or future:
“In today’s world parents find themselves at the mercy of a society which imposes pressures and priorities that allow neither time nor place for meaningful activities and relations between children and adults, which downgrade the role of parents and the functions of parenthood, and which prevent the parent from doing things he wants to do as a guide, friend, and companion to his children.”
—Urie Bronfenbrenner (b. 1917)
“Think of the many different relations of form and content. E.g., the many pairs of trousers and what’s in them.”
—Mason Cooley (b. 1927)
“The call of death is a call of love. Death can be sweet if we answer it in the affirmative, if we accept it as one of the great eternal forms of life and transformation.”
—Hermann Hesse (1877–1962)
“... the loss of belief in future states is politically, though certainly not spiritually, the most significant distinction between our present period and the centuries before. And this loss is definite. For no matter how religious our world may turn again, or how much authentic faith still exists in it, or how deeply our moral values may be rooted in our religious systems, the fear of hell is no longer among the motives which would prevent or stimulate the actions of a majority.”
—Hannah Arendt (1906–1975)