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.
In a comprehensive blog post titled "I wrote my own “proper” programming language," author Mukul Rathi chronicles the journey of designing and implementing a programming language from its nascent conceptual stages to a functional, albeit rudimentary, state. He meticulously details the process of building a compiler, breaking down the complex task into manageable, discrete steps.
The post begins by outlining the fundamental architecture of a compiler, illustrating the typical workflow from source code to executable program. This includes lexical analysis, where the input code is tokenized; parsing, which involves constructing an Abstract Syntax Tree (AST) to represent the code's structure; semantic analysis, where type checking and other semantic rules are enforced; and finally, code generation, where the AST is translated into intermediate representations like bytecode or assembly language.
Rathi delves into the specifics of his implementation, utilizing Python as the language for his compiler. He elucidates the lexical analyzer’s role in categorizing individual components of the source code, such as keywords, identifiers, and operators, transforming the raw text into a stream of meaningful tokens. The parsing stage, he explains, involves organizing these tokens into a hierarchical tree structure – the AST – which reflects the grammatical relationships between different parts of the code. This is achieved using a recursive descent parsing technique.
Furthermore, the post underscores the importance of semantic analysis, which goes beyond mere syntax verification and delves into the meaning of the code. This crucial step involves ensuring type compatibility, checking for undeclared variables, and enforcing other language-specific semantic rules. Rathi describes how his compiler performs these checks, thereby ensuring the logical integrity of the program.
Finally, the post culminates in a discussion of code generation. While stopping short of generating machine code directly, Rathi explains how his compiler generates bytecode, a lower-level representation of the program. This bytecode can then be executed by a virtual machine, effectively bridging the gap between high-level source code and the underlying hardware. He emphasizes that while his compiler does not perform all the optimizations a production-ready compiler would, it demonstrates the essential steps involved in translating a high-level programming language into an executable format. The post concludes by acknowledging the project's limitations while highlighting its educational value as a practical exercise in compiler construction.
Summary of Comments ( 13 )
https://news.ycombinator.com/item?id=42791036
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.
The Hacker News thread for "I wrote my own “proper” programming language (2020)" contains several comments discussing various aspects of the linked article.
Many comments focus on tooling and alternative approaches to building a programming language. One user suggests using tools like Lex/Yacc or Flex/Bison for lexical analysis and parsing, offering a more robust and less error-prone method than manual implementation. This comment sparked a small discussion thread with another user pointing out that while powerful, these tools can add complexity, especially for beginners. They advocate for a simpler approach initially, recommending a hand-rolled recursive descent parser for its educational value in understanding the underlying mechanisms. This exchange highlights the trade-off between ease of implementation and the robustness of the final product.
Another commenter discusses the evolution of compiler construction and how techniques and tools have changed over time. They specifically mention the shift towards using LLVM as a backend for code generation and optimization. This offers the advantage of targeting multiple platforms without rewriting the backend for each one.
Several users commend the author of the article for undertaking such a complex project and sharing their knowledge. They praise the clear explanations and the step-by-step approach presented in the article, finding it accessible even for those without prior compiler development experience.
Some comments delve into specific aspects of the implementation, such as garbage collection, with one commenter suggesting exploring different garbage collection strategies. Another thread discusses the performance implications of different language design choices, emphasizing the importance of considering efficiency from the start.
One user expresses a common sentiment among language developers, mentioning the inherent difficulty and complexity involved in creating a "proper" programming language. They acknowledge the effort required for not just initial implementation, but also ongoing maintenance and improvement.
Finally, a few comments express interest in the language's potential applications and its future development. They inquire about specific features and express a desire to see the project evolve.