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ICFP 2019
Sun 18 - Fri 23 August 2019 Berlin, Germany
Tue 20 Aug 2019 11:37 - 12:00 at Aurora Borealis - Program Analysis & Synthesis Chair(s): Daniel Winograd-Cort

Lenses are programs that can be run both “front to back” and “back to front,” allowing updates to either their source or their target data to be transferred in both directions. Since their introduction by Foster et al., lenses have been extensively studied, extended, and applied. Recent work has also demonstrated how techniques from type-directed program synthesis can be used to efficiently synthesize a simple class of lenses—so-called bijective lenses over string data—given a pair of types (regular expressions) and a small number of examples.

We extend this synthesis algorithm to a much broader class of lenses, called simple symmetric lenses, including all bijective lenses, all of the popular category of “asymmetric” lenses, and a rich subset of the more powerful “symmetric lenses” proposed by Hofmann et al. Intuitively, simple symmetric lenses allow some information to be present on one side but not the other and vice versa. They are of independent theoretical interest, being the largest class of symmetric lenses that do not rely on persistent internal state.

Synthesizing simple symmetric lenses is substantially more challenging than synthesizing bijective lenses: Since some of the information on each side can be “disconnected” from the other side, there will, in general, be many lenses that agree with a given example. To guide the search process, we use stochastic regular expressions and ideas from information theory to estimate the amount of information propagated by a candidate lens, generally preferring lenses that propagate more information, as well as user annotations marking parts of the source and target data structures as either irrelevant or essential.

We describe an implementation of simple symmetric lenses and our synthesis procedure as extensions to the Boomerang language. We evaluate its performance on 48 benchmark examples drawn from Flash Fill, Augeas, the bidirectional programming literature, and electronic file format synchronization tasks. Our implementation can synthesize each of these lenses in under 30 seconds.

Tue 20 Aug
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10:30 - 12:00: Program Analysis & SynthesisResearch Papers at Aurora Borealis
Chair(s): Daniel Winograd-CortTarget Corp
10:30 - 10:52
Relational Cost Analysis for Functional-Imperative Programs
Research Papers
Weihao QuUniversity at Buffalo, SUNY, Marco GaboardiUniversity at Buffalo, SUNY, Deepak GargMax Planck Institute for Software Systems
10:52 - 11:15
Fuzzi: A Three-Level Logic for Differential Privacy
Research Papers
Hengchu ZhangUniversity of Pennsylvania, Edo RothUniversity of Pennsylvania, Andreas HaeberlenUniversity of Pennsylvania, USA, Benjamin C. PierceUniversity of Pennsylvania, Aaron RothUniversity of Pennsylvania, USA
11:15 - 11:37
Synthesizing Differentially Private Programs
Research Papers
Calvin SmithUniversity of Wisconsin - Madison, Aws AlbarghouthiUniversity of Wisconsin-Madison
11:37 - 12:00
Synthesizing Symmetric Lenses
Research Papers
Anders MiltnerPrinceton University, Solomon MainaUniversity of Pennsylvania, Kathleen FisherTufts University, USA, Benjamin C. PierceUniversity of Pennsylvania, David WalkerPrinceton University, Steve ZdancewicUniversity of Pennsylvania