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:
“All social rules and all relations between individuals are eroded by a cash economy, avarice drags Pluto himself out of the bowels of the earth.”
—Karl Marx (1818–1883)
“I want relations which are not purely personal, based on purely personal qualities; but relations based upon some unanimous accord in truth or belief, and a harmony of purpose, rather than of personality. I am weary of personality.... Let us be easy and impersonal, not forever fingering over our own souls, and the souls of our acquaintances, but trying to create a new life, a new common life, a new complete tree of life from the roots that are within us.”
—D.H. (David Herbert)
“Your body must become familiar with its death—in all its possible forms and degrees—as a self-evident, imminent, and emotionally neutral step on the way towards the goal you have found worthy of your life.”
—Dag Hammarskjöld (1905–1961)
“Bobby read his future in women; his girls were omens, changes in the weather, and he’d sit all night in the Gentleman Loser waiting for the season to lay a new face down in front of him like a card.”
—William Gibson (b. 1948)