SN (Symbolic Notation)

SN is an experimental logic programming system built around symbolic expressions, conditional value sets (CVSs), and reversible computation. It is designed for symbolic reasoning, constraint solving, and introspective metaprogramming. SN has its own execution model, debugger, and memory management system, including a custom Promotional Garbage Collection (PGC) engine.

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Why SN?

Traditional programming languages evaluate expressions to single values. SN allows expressions to resolve to multiple symbolic values under different conditions, enabling advanced symbolic reasoning. It is especially suited for:

• Symbolic parsing (e.g., splitting strings based on grammar rules)
• Symbolic computation (e.g., Church numerals and combinators)
• Meta-level evaluation (reasoning about code itself)
• Deferred/delayed execution

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Key Concepts

Conditional Value Sets (CVSs)

A CVS is a set of values each paired with a conjunction of conditions. SN tracks these possibilities through evaluation, maintaining logical structure.

Meta Expressions

Expressions in SN can describe and manipulate other expressions. meta(x) and unmeta(x) let you move between levels of interpretation.

Stringrefs

Strings are represented as references to substrings, allowing symbolic decomposition, lookahead, and constraint propagation.

Promotional Garbage Collection (PGC)

PGC enables transactional memory with promotion logic that ensures memory is safely reused and updated when symbolic paths diverge. It supports both raw pointers ("backstabbing") and transaction-aware Ref<T> ("double dipping").

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Features

• Symbolic execution engine written in C++
• Debugger UI using Angular frontend
• Support for delayed evaluation and symbolic recursion (Y combinator)
• Modular validators like IsInteger, ParseInteger, IsFloatingPoint
• Support for Define, PartialAssert, and Evaluate() logic

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Current Status

SN is under active development. Core logic works and is tested. The system has a web-based debugger, but needs more documentation and testing. The goal is to make SN a robust engine for symbolic and logical experimentation.

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Getting Started

Build Requirements

• Visual Studio 2022
• CMake (optional)
• Angular CLI (for the frontend)

To Run:

1. Build SN backend (C++)
2. Start web debugger
3. Load debugger frontend (Angular)

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Contributing

We welcome contributors! Areas needing help:

• Writing unit tests
• Improving documentation
• Transitioning to Ref<T> model
• Debugger UI fixes

See [TODO.md] or GitHub issues for tasks.

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License

TBD. (Likely open-source)

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Author

Peter Driscoll, with help from ChatGPT and a pair of very clever dogs.

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Acknowledgements

Inspired by the beauty of functional programming, logic, and the joy of symbolic thinking.

"In a world full of values, SN dares to think in sets."