What is typed-sexp?

Typed-SEXP is a Rust library that lets developers write extensions for the R programming language with better safety guarantees. R is popular for statistics and data analysis, and people often write extensions in faster languages like C++ or Rust to speed up calculations. The problem is that R's internal interface for doing this is notoriously confusing and error-prone. This library gives developers a safer way to interact with R's internal data structures without adding heavy dependencies or complex tooling. At its core, the library wraps R's internal objects, called SEXP objects, in Rust's type system so that mistakes get caught before the code runs. It handles things like safely accessing elements of vectors and matrices, managing memory so objects don't get prematurely cleaned up by R's garbage collector, and calling R functions from Rust with properly typed arguments. It also works the other direction: you can embed R inside a Rust program and use R's capabilities from pure Rust code. The library deliberately stays close to R's actual internals rather than offering a polished, high-level wrapper. The intended user is someone who already understands how R works under the hood and wants to write R extensions in Rust without pulling in large macro-based frameworks. The author specifically avoids macros because they can be hard to debug and can confuse code analysis tools. Existing alternatives like Rcpp and extendr provide more abstraction, but this project takes a minimalist approach: enough type safety to prevent common mistakes, without hiding what's really happening. The project includes a few demos showing practical use cases: vector addition, matrix multiplication, calling closures passed from R, and embedding R in a Rust program. There's also a tongue-in-cheek project called "rasm" that implements inline assembly for R, which doubles as a stress test for the library's stability. The README notes that dynamically creating R functions from Rust is a planned feature but not yet implemented.