Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2010.16306

Lake symbols for island parsing

Katsumi Okuda·Shigeru Chiba
View original source ↗Read source document ↗Export metadata ↓

Abstract

Context: An island parser reads an input text and builds the parse (or abstract syntax) tree of only the programming constructs of interest in the text. These constructs are called islands and the rest of the text is called water, which the parser ignores and skips over. Since an island parser does not have to parse all the details of the input, it is often easy to develop but still useful enough for a number of software engineering tools. When a parser generator is used, the developer can implement an island parser by just describing a small number of grammar rules, for example, in Parsing Expression Grammar (PEG). Inquiry: In practice, however, the grammar rules are often complicated since the developer must define the water inside the island; otherwise, the island parsing will not reduce the total number of grammar rules. When describing the grammar rules for such water, the developer must consider other rules and enumerate a set of symbols, which we call alternative symbols. Due to this difficulty, island parsing seems to be not widely used today despite its usefulness in many applications. Approach: This paper proposes the lake symbols for addressing this difficulty in developing an island parser. It also presents an extension to PEG for supporting the lake symbols. The lake symbols automate the enumeration of the alternative symbols for the water inside an island. The paper proposes an algorithm for translating the extended PEG to the normal PEG, which can be given to an existing parser generator based on PEG. Knowledge: The user can use lake symbols to define water without specifying each alternative symbol. Our algorithms can calculate all alternative symbols for a lake symbol, based on where the lake symbol is used in the grammar. Grounding: We implemented a parser generator accepting our extended PEG and implemented 36 island parsers for Java and 20 island parsers for Python. Our experiments show that the lake symbols reduce 42 % of grammar rules for Java and 89 % of rules for Python on average, excluding the case where islands are expressions. Importance: This work eases the use of island parsing. Lake symbols enable the user to define the water inside the island simpler than before. Defining water inside the island is essential to apply island parsing for practical programming languages.

Explore related subjects

cs.PL

Keep this discovery

BibTeXRIS

Katsumi Okuda, Shigeru Chiba. 2020-10-30. Lake symbols for island parsing. https://doi.org/10.22152/programming-journal.org%2F2021%2F5%2F11

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

UnsafeChecker: Finding Soundness Bugs in Rust Safe Abstractions

Rust guarantees memory safety without garbage collection through a strict ownership and borrowing system. However, for low-level systems programming, many widely used libraries rely on the unsafe keyword. These libraries encapsulate raw-pointer operations behind safe APIs to form safe abstractions. A single mistake in this internal unsafe code can break its safety contract, rendering the abstraction unsound and allowing safe clients to trigger undefined behavior. Detecting these potential soundness violations is challenging. Existing static analysis tools for C/C++ ignore Rust-specific safety contracts, while current Rust tools lack the deep semantic modeling required to track the contexts that raw pointers erase. To address this gap, we present UnsafeChecker, a compiler-integrated static analysis framework for detecting potential soundness violations in Rust safe abstractions. UnsafeChecker analyzes Rust MIR using a flow-sensitive abstract interpretation that maintains a shared state with three components: ownership, object validity, and layout. Each warning rule consumes the subset of facts needed for the corresponding Rust safety obligation. UnsafeChecker reports both instruction-level undefined behavior and boundary-level contract violations that may escape through safe APIs. We evaluate UnsafeChecker on a benchmark of 46 RustSec vulnerabilities, which contain 53 ground-truth bugs. UnsafeChecker outperforms several state-of-the-art tools, detecting 32 CVEs and covering 36 bugs (67.9% recall) with 51.6% alert-level precision. Furthermore, in a large-scale scan of real-world crates on crates.io, UnsafeChecker uncovered 114 previously unknown bugs across 83 crates, with 45 confirmed and 27 already fixed by maintainers.

cs.PL↗
arXiv2026

Mapping Dynamic, Hierarchical Quantum Circuits

Qubit mapping is a critical pass in quantum compilation. Despite various advances, dynamic circuits, those exhibiting data dependent control-flow, often resulting from qubit measurements, are not yet supported by the vast majority of available qubit mappers. The crucial limitation to overcome is the dependence on flat, one-dimensional representations of circuits. Further, qubit mappers currently lack compiler abstractions that capture the hierarchical nature of circuits, hindering the qubit mapping process. In this paper, 1 we introduce a new qubit mapping method and analyses to tackle hierarchical dynamic circuits. Our novelty resides in four key aspects: modeling (statically) sub-circuits in disjoint control-flow paths, introducing a novel Qubit Reconciliation pass to maintain consistency between sub-circuit and control-flow boundaries, a loop-entry remapping pass, and a refined cost function enhanced for SWAP count, circuit depth, circuit latency and error. We demonstrate the efficiency of our approach on a wide range of dynamic circuits on two monolithic Quantum Processing Units of 127 and 156 qubits, and on chiplet hexagon-based QPUs. On monolithic QPUs, our qubit mapper improves the SWAP count by up to 52%, depth by up to 18%, latency by up to 18.6%, and error by up to 40%. On chiplet architectures, we achieve improvements of up to 36% on SWAP count, 8.7% on depth, 15% on latency, and 15% of error.

cs.PL↗
arXiv2026

Erased Postulates, Identity Types and Quotients

This text is concerned with the question of whether, in type theory with erasure annotations, one can postulate that some type is inhabited and still have a guarantee that a program will not get stuck. Previous work has provided such guarantees for consistent erased postulates, i.e. postulates that are restricted to be used in erased contexts. Here those guarantees are extended to type theory with identity types. Similar ideas provide a simple way to support quotient types: it is shown that one can let things like "the equivalence classes for two related values are equal" be erased postulates and have an eliminator that only computes for the equivalence class constructor, and still get a guarantee that programs will compute correctly. Another question is whether programs compute correctly if one is allowed to transport (cast) using erased identity proofs. It is shown that this is safe in the absence of quotients and postulates, and in the presence of quotients and erased postulates that can be implemented using equality reflection. However, unrestricted transports of this kind are not compatible with erased, postulated univalence. For that reason the text includes a study of the function []-cong, which encapsulates a limited form of transport for erased identity proofs. The text is accompanied by machine-checked Agda proofs.

cs.PL↗