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Questions tagged [future]

A placeholder for the result of a calculation before the calculation has completed. Used in concurrent programming. Questions about future events are off-topic on Stack Overflow.

A Wikipedia article on futures in concurrent programming.

A tutorial on concurrent programming in Java by Lars Vogel, including a section on futures and callables.

See also:

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What's the difference between a Future and a Promise?

What's the difference between Future and Promise? They both act like a placeholder for future results, but where is the main difference?
Evgenij Reznik
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What are the differences between Deferred, Promise and Future in JavaScript?

What are the differences between Deferreds, Promises and Futures? Is there a generally approved theory behind all these three?
Tower
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Waiting on a list of Future

I have a method which returns a List of futures List> futures = getFutures(); Now I want to wait until either all futures are done processing successfully or any of the tasks whose output is returned by a future throws an exception. Even…
user93796
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Futures vs. Promises

I'm confusing myself with difference between a future and a promise. Obviously, they have different methods and stuff, but what is the actual use case? Is it?: when I'm managing some async task, I use future to get the value "in future" when I'm…
Šimon Tóth
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135
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Transform Java Future into a CompletableFuture

Java 8 introduces CompletableFuture, a new implementation of Future that is composable (includes a bunch of thenXxx methods). I'd like to use this exclusively, but many of the libraries I want to use return only non-composable Future instances. Is…
Dan Midwood
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6 answers

Scala: List[Future] to Future[List] disregarding failed futures

I'm looking for a way to convert an arbitrary length list of Futures to a Future of List. I'm using Playframework, so ultimately, what I really want is a Future[Result], but to make things simpler, let's just say Future[List[Int]] The normal way to…
Joe
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How to create a completed future in java

What is the best way to construct a completed future in Java? I have implemented my own CompletedFuture below, but was hoping something like this that already exists. public class CompletedFuture implements Future { private final T…
Jake Walsh
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113
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4 answers

Get the status of a std::future

Is it possible to check if a std::future has finished or not? As far as I can tell the only way to do it would be to call wait_for with a zero duration and check if the status is ready or not, but is there a better way?
David Brown
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110
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4 answers

Dartlang wait more than one future

I want to do something after a lot of future functions are done, but I do not know how to write the code in dart? the code is like this: for (var d in data) { d.loadData().then() } // when all loaded // do something here but I don't want to wait…
bitnick
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Pass multiple parameters to concurrent.futures.Executor.map?

The concurrent.futures.Executor.map takes a variable number of iterables from which the function given is called. How should I call it if I have a generator that produces tuples that are normally unpacked in place? The following doesn't work because…
Matt Joiner
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3 answers

When should I use a FutureBuilder?

I was wondering when I should use the future builder. For example, if I want to make an http request and show the results in a list view, as soon as you open the view, should I have to use the future builder or just build a ListViewBuilder like: new…
Little Monkey
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101
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6 answers

Promise equivalent in C#

In Scala there is a Promise class that could be used to complete a Future manually. I am looking for an alternative in C#. I am writing a test and I want it to look it similar to this: // var MyResult has a field `Header` var promise = new…
eddyP23
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100
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Combine awaitables like Promise.all

In asynchronous JavaScript, it is easy to run tasks in parallel and wait for all of them to complete using Promise.all: async function bar(i) { console.log('started', i); await delay(1000); console.log('finished', i); } async function foo()…
Tamas Hegedus
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6 answers

Dart, how to create a future to return in your own functions?

is it possible to create your own futures in Dart to return from your methods, or must you always return a built in future return from one of the dart async libraries methods? I want to define a function which always returns a Future>…
Daniel Robinson
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5 answers

Why should I use std::async?

I'm trying to explore all the options of the new C++11 standard in depth, while using std::async and reading its definition, I noticed 2 things, at least under linux with gcc 4.8.1 : it's called async, but it got a really "sequential behaviour",…
user2485710
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