langcc: A Next-Generation Compiler Compiler

Traditionally, parsing has been a laborious and error-prone component of compiler development, and most parsers for full industrial programming languages are still written by hand. The author [Zim22] shows that automatic parser generation can be practical, via a number of new innovations upon the standard LR paradigm of Knuth et al. With this methodology, we can automatically generate efficient parsers for virtually all languages that are intuitively "easy to parse". This includes Golang 1.17.8 and Python 3.9.12, for which our generated parsers are, respectively, 1.2x and 4.3x faster than the standard parsers. This document is a companion technical report which describes the software implementation of that work, which is available open-source at https://github.com/jzimmerman/langcc

Practical LR Parser Generation

Parsing is a fundamental building block in modern compilers, and for industrial programming languages, it is a surprisingly involved task. There are known approaches to generate parsers automatically, but the prevailing consensus is that automatic parser generation is not practical for real programming languages: LR/LALR parsers are considered to be far too restrictive in the grammars they support, and LR parsers are often considered too inefficient in practice. As a result, virtually all modern languages use recursive-descent parsers written by hand, a lengthy and error-prone process that dramatically increases the barrier to new programming language development. In this work we demonstrate that, contrary to the prevailing consensus, we can have the best of both worlds: for a very general, practical class of grammars -- a strict superset of Knuth's canonical LR -- we can generate parsers automatically, and the resulting parser code, as well as the generation procedure itself, is highly efficient. This advance relies on several new ideas, including novel automata optimization procedures; a new grammar transformation ("CPS"); per-symbol attributes; recursive-descent actions; and an extension of canonical LR parsing, which we refer to as XLR, which endows shift/reduce parsers with the power of bounded nondeterministic choice. With these ingredients, we can automatically generate efficient parsers for virtually all programming languages that are intuitively easy to parse -- a claim we support experimentally, by implementing the new algorithms in a new software tool called langcc, and running them on syntax specifications for Golang 1.17.8 and Python 3.9.12. The tool handles both languages automatically, and the generated code, when run on standard codebases, is 1.2x faster than the corresponding hand-written parser for Golang, and 4.3x faster than the CPython parser, respectively

Privacy-Preserving Shortest Path Computation

Navigation is one of the most popular cloud computing services. But in virtually all cloud-based navigation systems, the client must reveal her location and destination to the cloud service provider in order to learn the fastest route. In this work, we present a cryptographic protocol for navigation on city streets that provides privacy for both the client's location and the service provider's routing data. Our key ingredient is a novel method for compressing the next-hop routing matrices in networks such as city street maps. Applying our compression method to the map of Los Angeles, for example, we achieve over tenfold reduction in the representation size. In conjunction with other cryptographic techniques, this compressed representation results in an efficient protocol suitable for fully-private real-time navigation on city streets. We demonstrate the practicality of our protocol by benchmarking it on real street map data for major cities such as San Francisco and Washington, D.C.Comment: Extended version of NDSS 2016 pape

Just-in-time Delivery of Text-to-speech Playback

In an interaction between a virtual assistant and a user, it is often the case that the responses of the virtual assistant arrive just after the passage of critical events in the user’s timeline. For example, navigational instructions to exit a freeway sometimes arrive just a bit too late to take the off-ramp. Some of this latency is attributable to the very nature of spoken audio playback: spoken audio playback being a linear medium, the length of time required for the spoken content to play can affect the accuracy of time-sensitive actions. This disclosure describes techniques that take into account the length of a response to be provided to the user such that the response is delivered in a timely manner with sufficient allowance for reaction time

Financing Options for Local Government

In this session, attendees will learn how the Indiana Bond Bank (IBB) can be an asset to local government. The IBB provides financing options for essential equipment, short-term infrastructure projects, and fuel budgeting; is set up to assist with debt issuance; and exempts the need to bid the financing. Officials from INDOT and the City of Lafayette will offer their insight on how the IBB may benefit your organization or community

From Beyond the Stars: Innovation and Inspiration in Meiji Japanese Art, 1868-1912

Design by Tom Wagner. Photography by the Kruizenga Art Museum, Tom Wagner, and Curatorial Assistance/WorldBridge Art, Inc. Produced by Storming the Castle Pictures (StCP) for the Kruizenga Art Museum as a catalogue for the exhibition, From Beyond the Stars, August 29 - December 16, 2017. Photographs, text and design copyright 2017 Hope College and Tom Wagner, no reproduction or use of any material, in whole or in part, without the written permission of Hope College.https://digitalcommons.hope.edu/kam_catalogs/1001/thumbnail.jp

Stochastic Ordering under Conditional Modelling of Extreme Values: Drug-Induced Liver Injury

Drug-induced liver injury (DILI) is a major public health issue and of serious concern for the pharmaceutical industry. Early detection of signs of a drug's potential for DILI is vital for pharmaceutical companies' evaluation of new drugs. A combination of extreme values of liver specific variables indicate potential DILI (Hy's Law). We estimate the probability of severe DILI using the Heffernan and Tawn (2004) conditional dependence model which arises naturally in applications where a multidimensional random variable is extreme in at least one component. We extend the current model by including the assumption of stochastically ordered survival curves for different doses in a Phase 3 study.Comment: 24 pages, 5 figure

Building Environmentally Sustainable Communities: A Framework for Inclusivity

Reviews literature on past inequitable and unsustainable urban development and visions for linking sustainability, opportunity, and inclusion. Analyzes possible metrics for measuring sustainability and access as well as next steps for policy

Advanced sensors and instrumentation

NASA is currently investigating the readiness of Advanced Sensors and Instrumentation to meet the requirements of new initiatives in space. The following technical objectives and technologies are briefly discussed: smart and nonintrusive sensors; onboard signal and data processing; high capacity and rate adaptive data acquisition systems; onboard computing; high capacity and rate onboard storage; efficient onboard data distribution; high capacity telemetry; ground and flight test support instrumentation; power distribution; and workstations, video/lighting. The requirements for high fidelity data (accuracy, frequency, quantity, spatial resolution) in hostile environments will continue to push the technology developers and users to extend the performance of their products and to develop new generations