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  • Oliver Bračevac
  • Nada Amin
  • Guido Salvaneschi
  • Sebastian Erdweg
  • Patrick Eugster
  • Mira Mezini
We present the first language design to uniformly express variants of n-way joins over asynchronous event streams from different domains, e.g., stream-relational algebra, event processing, reactive and concurrent programming. We model asynchronous reactive programs and joins in direct style, on top of algebraic effects and handlers. Effect handlers act as modular interpreters of event notifications, enabling fine-grained control abstractions and customizable event matching. Join variants can be considered as cartesian product computations with ”degenerate” control flow, such that unnecessary tuples are not materialized a priori. Based on this computational interpretation, we decompose joins into a generic, naive enumeration procedure of the cartesian product, plus variant-specific extensions, represented in terms of user-supplied effect handlers. Our microbenchmarks validate that this extensible design avoids needless materialization. Alongside a formal semantics for joining and prototypes in Koka and multicore OCaml, we contribute a systematic comparison of the covered domains and features.
Original languageEnglish
Article number67
Pages (from-to)1-31
Number of pages31
JournalProceedings of the ACM on Programming Languages
Volume2
Issue numberICFP
DOIs
Publication statusPublished - 2018

ID: 51567028