Abstract
The ordinary untyped -calculus has a -theoretic model proposed in two related forms by Scott and Plotkin in the 1970s. Recently Scott showed how to introduce probability by extending these models with random variables. However, to reason about correctness and to add further features, it is useful to reinterpret the construction in a higher-order Boolean-valued model involving a measure algebra. We develop the semantics of an extended stochastic -calculus suitable for modeling a simple higher-order probabilistic programming language. We exhibit a number of key equations satisfied by the terms of our language. The terms are interpreted using a continuation-style semantics with an additional argument, an infinite sequence of coin tosses, which serves as a source of randomness. We also introduce a fixpoint operator as a new syntactic construct, as Β-reduction turns out not to be sound for unrestricted terms. Finally, we develop a new notion of equality between terms interpreted in a measure algebra, allowing one to reason about terms that may not be equal almost everywhere. This provides a new framework and reasoning principles for probabilistic programs and their higher-order properties.
Original language | English |
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Title of host publication | LICS '18 : Proceedings of the 33rd Annual ACM/IEEE Symposium on Logic in Computer Science |
Place of Publication | Piscataway, NJ. |
Pages | 669-678 |
Number of pages | 10 |
DOIs | |
Publication status | Published - 9 Jul 2018 |
Event | 33rd Annual ACM/IEEE Symposium on Logic in Computer Science, LICS 2018 - Oxford, United Kingdom Duration: 9 Jul 2018 → 12 Jul 2018 |
Conference
Conference | 33rd Annual ACM/IEEE Symposium on Logic in Computer Science, LICS 2018 |
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Country/Territory | United Kingdom |
City | Oxford |
Period | 9/07/18 → 12/07/18 |
Funding
This research was supported by the DFF Danish research grant FNU 4181-00360, by a grant from NSERC (Canada), and by a grant from the National Science Foundation (USA). We gratefully acknowledge the support of the Simons Institute Logical Structures in Computation Program in Fall 2016. We thank Ugo Dal Lago, Cameron Freer, Marco Gaobardi, Chris Heunen, Alex Simpson and Sam Staton for useful discussions.
Keywords
- boolean-valued models
- denotational semantics
- random variables
- stochastic λ-calculus