Fri 12 Jan 2018 11:45 - 12:10 at Watercourt - Dynamic Languages Chair(s): Jean Yang

Given a tower of interpreters, i.e., a sequence of multiple interpreters interpreting one another as input programs, we aim to collapse this tower into a compiler that removes all interpretive overhead and runs in a single pass. In the real world, a use case might be Python code executed by an x86 runtime, on a CPU emulated in a JavaScript VM, running on an ARM CPU. Collapsing such a tower can not only exponentially improve runtime performance, but also enable the use of base-language tools for interpreted programs, e.g., for analysis and verification. In this paper, we lay the foundations in an idealized but realistic setting.

We present a multi-level lambda calculus that features staging constructs and stage polymorphism: based on runtime parameters, an evaluator either executes source code (thereby acting as an interpreter) or generates code (thereby acting as a compiler). We identify stage polymorphism, a programming model from the domain of high-performance program generators, as the key mechanism to make such interpreters compose in a collapsible way.

We present Pink, a meta-circular Lisp-like evaluator on top of this calculus, and demonstrate that we can collapse arbitrarily many levels of self-interpretation, including levels with semantic modi cations. We discuss several examples: compiling regular expressions through an interpreter to base code, building program transformers from modified interpreters, and others. We develop these ideas further to include re reflection and reification, culminating in Purple, a reflective language inspired by Brown, Blond, and Black, which realizes a conceptually infinite tower, where every aspect of the semantics can change dynamically. Addressing an open challenge, we show how user programs can be compiled and recompiled under user-modified semantics.

Fri 12 Jan
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10:30 - 12:10: Research Papers - Dynamic Languages at Watercourt
Chair(s): Jean YangCarnegie Mellon University
POPL-2018-papers10:30 - 10:55
Olivier FlückigerNortheastern University, USA, Gabriel SchererNortheastern University, USA, Ming-Ho YeeNortheastern University, USA, Aviral GoelNortheastern University, Amal AhmedNortheastern University, USA, Jan VitekNortheastern University
DOI Pre-print
POPL-2018-papers10:55 - 11:20
José Fragoso SantosImperial College London, Petar MaksimovićImperial College London, Daiva NaudžiūnienėImperial College London, Thomas WoodImperial College London, Philippa GardnerImperial College London
POPL-2018-papers11:20 - 11:45
Phúc C. NguyễnUniversity of Maryland, Thomas GilrayUniversity of Maryland, Sam Tobin-HochstadtIndiana University, David Van HornUniversity of Maryland
POPL-2018-papers11:45 - 12:10
Nada AminUniversity of Cambridge, Tiark RompfPurdue University