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In [[computer science]], a '''promise''' (also known as a '''future''' in some languages) is a proxy for a result that is not yet known, usually because the computation of its value has not yet completed. They were introduced in [[1977]] in the paper by [[Henry Baker (computer scientist)|Henry Baker]] and [[Carl Hewitt]]. The use of promises (futuures) can dramatically reduce latency in [[distributed computing|distributed systems]]. ''E.g.'', it enables pipelining of messages, called '''promise pipelining''' [http://www.erights.org/elib/distrib/pipeline.html] [http://c2.com/cgi/wiki?PromisePipelining].
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The ''promise'' (''future'') construct became more better known by its inclusion in programming lannguages such as [[MultiLisp]] and [[Actor model|Act1]]. The use of logic variables for communication in concurrent logic programming languages is quite similar. These started with "Prolog with Freeze" and "IC Prolog", and became a true concurrency primitive with Concurrent Prolog, Flat Concurrent Prolog, Parlog, Vulcan, Janus, Mozart/Oz, Flow Java, and Alice. The single assignment "I-var" from data flow languages, included in Reppy's "Concurrent ML", is much like the concurrent logic variable.
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