SwiftStan

1. A macOS / Xcode / Swift CLI wrapping Stan's cmdstan.

2. An experimental port of McElreath's R implementation ulam() in rethinking to Swift.

3. As an "experiment within an experiment", and for me to further my understanding of the mapping back-and-forth between alternate ways of expressing Stan Language Programs, I asked Claude to plan and implement a reverse mapping from a .stan file to an .alist.r file. See sections 2.2 and 5.2 in Docs/UlamManual.md.

Documentation lives in Docs/:

• Docs/UserGuide.md — Overview, supported functionality, setup and usage.
• Docs/UlamManual.md — Ulam pipeline manual (stancode → csv2json → CMDSTAN).
• Docs/DSLManual.md — Swift+DSL pipeline (alist2dsl → dsl2stan → csv2json → CMDSTAN).
• Docs/TODO.md — Future work items.
• CLAUDE.md — Guidance for Claude.

As the last item indicates, the ulam port is being worked on using Claude.

Example cases

The repository contains ready-to-run input files for several of the models used in the ulam and DSL manuals and also models from "Statistical Rethinking", typically ending with "...m[n][n]", e.g. "milk_m5_7". Those can be found in the top-level Examples/ directory. Each example is a self-contained case directory named after the model:

Examples/<name>/
├── Preliminaries/     the inputs (<name>.csv, <name>.alist.R, and for the DSL cases <Name>.ulam.swift)
└── Results/           empty — the pipeline writes its output here

Once SwiftStan has been installed (see UserGuide.md), to run the examples, copy the contents of the Examples directory into your ~/Documents/<STAN_CASES>/ root and run the pipeline against it. For example:

cd ~/Project/Swift/SwiftStan # Your path to SwiftStan
cp -Rf Examples/* ~/Documents/StanCases/ # Your <Stan_Cases> environment variable
swiftstan ulam --model howell_m4_4