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Snobol/Spitbol Browser-centric IDE (snobol.dev)

July 1, 2025

The Application

đź‘‹ The Snobol/Spitbol web application discussed below can be found at snobol.dev

The Motivation

SNOBOL4 stands out as one of the most fascinating historical programming languages I’ve encountered. Developed at Bell Labs in the 1960s, SNOBOL4 quickly proved to be more captivating than the original research project it was created to support.

SNOBOL4 is unlike any other language. It lacks familiar constructs like IF/THEN statements and DO loops, yet its distinctive success/failure paradigm, combined with “alternative evaluation” and “inherited failure” enables powerful and implicit flow control.

SNOBOL4 is a very high-level language that is paradoxically both loosely and strongly typed: you can change a variable’s datatype simply by assigning a new value, but the system always tracks types and prevents misuse, performing automatic conversions when possible. The language excels at data format conversion, manipulating data representations and linked data structures, handling all kinds of character strings, and solving memory management problems. Its pattern matching and string parsing capabilities are arguably the most advanced of any language in its class.

The Pitfall

Because SNOBOL4 is so unique, and now over 60 years old, it can be challenging to use, especially when we’re accustomed to the conveniences of modern development environments. Coding as if it were still 1981 is a hard sell; nobody is going to sit there and say ‘this is nice’.

Integrating SNOBOL4 with tools like VSCode is particularly tricky due to the language’s peculiarities. Four years ago I created what I believe is the only VSCode syntax highlighter for SNOBOL4, but stopped there. While more is possible, I concluded that building a browser-based IDE would be the fastest and most effective solution.

The Solution

I developed a web application using SvelteKit (hosted on Vercel) that serves as an IDE, alongside a WASM compilation of CSNOBOL (SNOBOL4) by Phil Budne that allows for instant code execution on your own computer. As a secondary option, there is also a localhost server (built with Bun and TypeScript) which listens for requests and passes them to your personal CSNOBOL or Spitbol compiler.

Some key features I wanted and therefore implemented include:

  • Automatic compilation with every keystroke. SNOBOL (especially Spitbol) compiles incredibly fast. For most datasets, you get immediate feedback.

  • Inline error messages. I dislike having to hunt down line numbers and manually invoke the compiler. I want that instant, “hot reload” experience.

  • Ability to spawn additional code windows with the same code, making it easy to prototype and experiment with different ideas.

  • Basic linting for issues like unused branches (GOTO statements) or DEFINE statements without labels.

  • All code is processed locally and never leaves your machine.

The last point is especially important, as many web-based IDEs require you to upload your code, which can be a privacy concern. I briefly thought about remote code execution, but with WASM there simply is no benefit or value given the security challenges around nefarious code injection and additional overhead.

I’m definitely open to collaborating with anyone interested in rewriting the localhost backend method using CSNOBOL, especially since it includes socket capabilities that could make this integration both powerful, and thematically correct in the sense this is a SNOBOL IDE afterall! The current implementation uses Bun, a high-performance TypeScript runtime, simply because I’m most familiar with its ecosystem and it offers excellent speed and efficiency to allow compilation on every keystroke.

Error Message Integration

Over the years, SNOBOL has evolved into several notable variants. The two most prominent today are:

Spitbol: A high-performance SNOBOL4 implementation for Linux and other Unix-like systems, available only for 64-bit x86_64 architectures. While Spitbol is robust and fast, there is currently no modern Win64 version—a gap I may address by attempting a cross-compilation in the future.

CSNOBOL: Phil Budne’s well-maintained version supporting both Unix-like systems and Windows, which continues to receive updates, with the latest release as recent as May 2025.

The inline error message system I’ve developed supports both Spitbol and CSNOBOL. Each compiler reports line numbers and error details in its own way, so the IDE parses and processes these outputs to present clear, contextual feedback directly within the code editor. This ensures that no matter which SNOBOL variant you’re using, you receive immediate and accurate error information as you work.

A compelling future enhancement would be to integrate Andrew Koenig’s SNOCONE, a language that extends SNOBOL4 by adding traditional control structures such as if/then/else, do, and while.

Closing Remarks

I’ll be the first to admit - I’m not an expert in SNOBOL! I’m not even sure I’m good at it. This project is really a way for me to deepen my understanding of the language by using it more extensively. As a result, there are probably some gaps and rough edges that still need attention, so I’m actively seeking community feedback (admin |at| snobol |dot| dev) and reports of anything that doesn’t work as expected.

Looking ahead, I plan to add many more coding examples, likely drawing from sources like Rosettta Code and Ralph’s books. Additionally, I want to convert the existing SNOBOL manuals into markdown format and make them searchable directly within the tool. This should make it much easier to find information without having to dig through PDF manuals. Thanks for reading!

Community

If you’re interested in SNOBOL or talking about the IDE, join the dicussions at either the SNOBOL Discord Group or Groups.io!