Xee is a new XPath and XSLT engine written in Rust, focusing on performance, security, and WebAssembly compatibility. It aims to be a modern alternative to existing engines, offering a safe and efficient way to process XML and HTML in various environments, including browsers and servers. Leveraging Rust's ownership model and memory safety features, Xee minimizes vulnerabilities like use-after-free errors and buffer overflows. Its WebAssembly support enables client-side XML processing without relying on JavaScript, potentially improving performance and security for web applications. While still under active development, Xee already supports a substantial portion of the XPath 3.1 and XSLT 3.0 specifications, with plans to implement streaming transformations and other advanced features in the future.
A critical vulnerability was discovered impacting multiple SAML single sign-on (SSO) libraries across various programming languages. This vulnerability stemmed from inconsistencies in how different XML parsers interpret and handle XML signatures within SAML assertions. Attackers could exploit these "parser differentials" by crafting malicious SAML responses where the signature appeared valid to the service provider's parser but actually signed different data than what the identity provider intended. This allowed attackers to potentially impersonate any user, gaining unauthorized access to systems protected by vulnerable SAML implementations. The blog post details the vulnerability's root cause, demonstrates exploitation scenarios, and lists the affected libraries and their patched versions.
Hacker News commenters discuss the complexity of SAML and the difficulty of ensuring consistent parsing across different implementations. Several point out that this vulnerability highlights the inherent fragility of relying on complex, XML-based standards like SAML, especially when multiple identity providers and service providers are involved. Some suggest that simpler authentication methods would be less susceptible to such parsing discrepancies. The discussion also touches on the importance of security audits and thorough testing, particularly for critical systems relying on SSO. A few commenters expressed surprise that such a vulnerability could exist, highlighting the subtle nature of the exploit. The overall sentiment reflects a concern about the complexity and potential security risks associated with SAML implementations.
C Plus Prolog is a project that embeds a Prolog interpreter within C++ code, allowing for logic programming within a C++ application. It aims to provide a seamless integration where Prolog predicates can be called directly from C++ and vice-versa, enabling the combination of Prolog's declarative power with C++'s performance and imperative features. The project leverages a modified version of SWI-Prolog, a popular open-source Prolog implementation, and offers a bidirectional interface for data exchange between the two languages. This facilitates the development of applications that benefit from both efficient procedural code and the logical reasoning capabilities of Prolog.
Hacker News users discussed the practicality and niche appeal of C Plus Prolog. Some expressed interest in its potential for specific applications like implementing rule engines or program analysis tools, while others questioned the performance implications of embedding Prolog within C++. One commenter suggested that a cleaner approach might involve interfacing Prolog with a language like Rust. Several pointed out the project's age and apparent inactivity, raising concerns about maintainability and documentation. The potential for improved tooling using C++-based IDEs was mentioned as a possible benefit. Overall, the discussion centered around the specialized nature of the project and the trade-offs involved in its approach.
The author seeks a C-like language with modern features like generics, modules, and memory safety, while maintaining C's performance and close-to-the-metal nature. They desire a language suitable for systems programming, potentially as a replacement for C in performance-critical applications, but with the added benefits of contemporary language design. They are exploring if such a language already exists or whether retrofitting C would be a more viable approach. Essentially, they want the power and control of C without its inherent pitfalls and limitations.
The Hacker News comments discuss the practicality and potential benefits of a "retrofitted" C dialect, primarily focusing on memory safety. Some suggest exploring existing options like Zig, Rust, or Odin, which already address many of C's shortcomings. Others express skepticism about the feasibility of such a project, citing the complexity of C's ecosystem and the difficulty of maintaining compatibility while introducing significant changes. A few commenters propose specific improvements, such as optional garbage collection or stricter type checking, but acknowledge the challenges in implementation and adoption. There's a general agreement that memory safety is crucial, but opinions diverge on whether a new dialect or focusing on tooling and better practices within existing C is the best approach. Some also discuss the potential benefits for embedded systems, where C remains dominant.
Ohm is a parsing toolkit designed for creating parsers in JavaScript and TypeScript that are both powerful and easy to use. It features a grammar definition syntax closely resembling EBNF, enabling developers to express complex syntax rules clearly and concisely. Ohm's built-in support for semantic actions allows users to directly embed JavaScript or TypeScript code within their grammar rules, simplifying the process of building abstract syntax trees (ASTs) and performing other actions during parsing. The toolkit provides excellent error reporting capabilities, helping developers quickly identify and fix syntax errors. Its flexible architecture makes it suitable for various applications, from validating user input to building full-fledged compilers and interpreters.
HN users generally expressed interest in Ohm, praising its user-friendliness, clear documentation, and the power offered by its grammar-based approach to parsing. Several compared it favorably to traditional parser generators like PEG.js and nearley, highlighting Ohm's superior error messages and easier learning curve. Some users discussed potential applications, including building linters, formatters, and domain-specific languages. A few questioned the performance implications of its JavaScript implementation, while others suggested potential improvements like adding support for left-recursive grammars. The overall sentiment leaned positive, with many eager to try Ohm in their own projects.
"Trails of Wind" is a generative art project exploring the visualization of wind currents. Using weather data, the artwork dynamically renders swirling lines that represent the movement and direction of wind across a global map. The piece allows viewers to observe complex patterns and the interconnectedness of global weather systems, offering an aesthetic interpretation of otherwise invisible natural forces. The project emphasizes the ever-shifting nature of wind, resulting in a constantly evolving artwork.
HN users largely praised the visual aesthetic and interactive elements of "Trails of Wind," describing it as mesmerizing, beautiful, and relaxing. Some appreciated the technical aspect, noting the clever use of WebGL and shaders. Several commenters pointed out the similarity to the older "wind map" visualizations, while others drew comparisons to other flow visualizations and generative art pieces. A few users wished for additional features like zooming, different data sources, or adjustable parameters. One commenter raised the concern about the project's longevity and the potential for the underlying data source to disappear.
Mukul Rathi details his journey of creating a custom programming language, focusing on the compiler construction process. He explains the key stages involved, from lexing (converting source code into tokens) and parsing (creating an Abstract Syntax Tree) to code generation and optimization. Rathi uses his language, which he implements in OCaml, to illustrate these concepts, providing code examples and explanations of how each component works together to transform high-level code into executable machine instructions. He emphasizes the importance of understanding these foundational principles for anyone interested in building their own language or gaining a deeper appreciation for how programming languages function.
Hacker News users generally praised the article for its clarity and accessibility in explaining compiler construction. Several commenters appreciated the author's approach of building a complete, albeit simple, language instead of just a toy example. Some pointed out the project's similarity to the "Let's Build a Compiler" series, while others suggested alternative or supplementary resources like Crafting Interpreters and the LLVM tutorial. A few users discussed the tradeoffs between hand-written lexers/parsers and using parser generator tools, and the challenges of garbage collection implementation. One commenter shared their personal experience of writing a language and the surprising complexity of seemingly simple features.
"Zork: The Great Inner Workings" explores the technical underpinnings of the classic text adventure game, Zork. The article dives into its creation using the MDL programming language, highlighting its object-oriented design before such concepts were widespread. It explains how Zork's world is represented through a network of interconnected rooms and objects, managed through a sophisticated parser that interprets player commands. The piece also touches upon the game's evolution from its mainframe origins to its later commercial releases, illustrating how its internal structure allowed for complex interactions and a rich, immersive experience despite the limitations of text-based gaming.
Hacker News users discuss the technical ingenuity of Zork's implementation, particularly its virtual machine and memory management within the limited hardware constraints of the time. Several commenters reminisce about playing Zork and other Infocom games, highlighting the engaging narrative and parser. The discussion also touches on the cultural impact of Zork and interactive fiction, with mentions of its influence on later games and the enduring appeal of text-based adventures. Some commenters delve into the inner workings described in the article, appreciating the explanation of the Z-machine and its portability. The clever use of dynamic memory allocation and object representation is also praised.
The article explores rule-based programming as a powerful, albeit underutilized, approach to creating interactive fiction. It argues that defining game logic through a set of declarative rules, rather than procedural code, offers significant advantages in terms of maintainability, extensibility, and expressiveness. This approach allows for more complex interactions and emergent behavior, as the game engine processes the rules to determine outcomes, rather than relying on pre-scripted sequences. The author advocates for a system where rules define relationships between objects and actions, enabling dynamic responses to player input and fostering a more reactive and believable game world. This, they suggest, leads to a more natural feeling narrative and simpler development, especially for managing complex game states.
HN users discuss the merits and drawbacks of rule-based programming for interactive fiction, specifically in Inform 7. Some argue that while appearing simpler initially, rule-based systems can become complex and difficult to debug as interactions grow, leading to unpredictable behavior. Others appreciate the declarative nature and find it well-suited for IF's logic, particularly for handling complex scenarios with many objects and states. The potential performance implications of a rule-based engine are also raised. Several commenters express nostalgia for older IF systems and debate the balance between authoring complexity and expressive power offered by different programming paradigms. A recurring theme is the importance of choosing the right tool for the job, acknowledging that rule-based approaches might be ideal for some types of IF but not others. Finally, some users highlight the benefits of declarative programming for expressing relationships and constraints clearly.
This blog post explores a simplified variant of Generalized LR (GLR) parsing called "right-nulled" GLR. Instead of maintaining a graph-structured stack during parsing ambiguities, this technique uses a single stack and resolves conflicts by prioritizing reduce actions over shift actions. When a conflict occurs, the parser performs all possible reductions before attempting to shift. This approach sacrifices some of GLR's generality, as it cannot handle all types of grammars, but it significantly reduces the complexity and overhead associated with maintaining the graph-structured stack, leading to a faster and more memory-efficient parser. The post provides a conceptual overview, highlights the limitations compared to full GLR, and demonstrates the algorithm with a simple example.
Hacker News users discuss the practicality and efficiency of GLR parsing, particularly in comparison to other parsing techniques. Some commenters highlight its theoretical power and ability to handle ambiguous grammars, while acknowledging its potential performance overhead. Others question its suitability for real-world applications, suggesting that simpler methods like PEG or recursive descent parsers are often sufficient and more efficient. A few users mention specific use cases where GLR parsing shines, such as language servers and situations requiring robust error recovery. The overall sentiment leans towards appreciating GLR's theoretical elegance but expressing reservations about its widespread adoption due to perceived complexity and performance concerns. A recurring theme is the trade-off between parsing power and practical efficiency.
Summary of Comments ( 16 )
https://news.ycombinator.com/item?id=43502291
HN commenters generally praise Xee's speed and the author's approach to error handling. Several highlight the impressive performance benchmarks compared to libxml2, with some noting the potential for Xee to become a valuable tool in performance-sensitive XML processing scenarios. Others appreciate the clean API design and Rust's memory safety advantages. A few discuss the niche nature of XPath/XSLT in modern development, while some express interest in using Xee for specific tasks like web scraping and configuration parsing. The Rust implementation also sparked discussions about language choices for performance-critical applications. Several users inquire about WASM support, indicating potential interest in browser-based applications.
The Hacker News post discussing Xee, a modern XPath and XSLT engine written in Rust, has generated several comments exploring various aspects of the project.
Several commenters express enthusiasm for the project, particularly praising its performance. One user highlights the speed improvements observed in their own testing, emphasizing the significance of a faster XSLT engine for their workflow. Another commenter points out the potential benefits of Rust's memory safety features for preventing crashes and improving the overall reliability of the engine. The choice of Rust itself is lauded, with several comments mentioning its growing popularity and suitability for tasks demanding performance and safety.
Some discussion revolves around the complexities of XPath and XSLT, acknowledging their power while also noting the steep learning curve. One commenter mentions their infrequent use of these technologies, expressing interest in revisiting them with a tool like Xee. Another points to the niche nature of XSLT, suggesting its relevance primarily within specific industries or for particular tasks like XML transformations.
A few comments delve into technical details. One user asks about the engine's handling of extensions, a crucial feature for extending the functionality of XPath and XSLT. Another inquires about the implementation of the
document()function and its behavior. The creator of Xee actively participates in the thread, responding to these technical queries and providing insights into the project's design choices and future plans. They discuss the challenges of supporting extensions and outline potential approaches for implementing them.The conversation also touches on alternative XPath and XSLT engines, with mentions of Libxml2 and Saxon. Comparisons are drawn in terms of performance and features, highlighting Xee's potential advantages in certain areas.
Overall, the comments reflect a positive reception towards Xee. Commenters express interest in its performance gains and the potential of Rust for creating robust and efficient XML processing tools. The discussion also acknowledges the complexities of XPath and XSLT, and explores technical nuances of the engine's implementation and its place within the existing ecosystem of XML processing tools.