Further Reading: Fortran 2023 and Beyond

This is a moving target, so the best sources here are living ones — the community hub, the committee's own papers, and each compiler's status page — rather than any fixed printed reference. Prefer primary sources, and treat feature-support claims (including this chapter's) as dated snapshots to re-check. Everything below is Tier 1 (canonical/primary) or Tier 2 (authoritative but fast-changing); nothing here should be quoted as a permanent fact about what compiles today.

The standard and its guides

• ISO/IEC 1539-1:2023, Information technology — Programming languages — Fortran (Tier 1). The Fortran 2023 standard itself — the definitive word on every feature in §39.1. The final document is sold by ISO, but late public working drafts of each revision are made available through the committee (see below) and are what most people actually read.
• Metcalf, Reid & Cohen, Modern Fortran Explained (Tier 1). The standard-tracking reference; its editions follow the revisions, and the most recent covers the Fortran 2023 additions with the committee's own authority (Reid was long the editor of the standard). The book to own if you want the features explained rigorously rather than surveyed.

The ecosystem, online

• fortran-lang.org (Tier 1). The hub of the renaissance in §39.3: tutorials, news, and the gateways to fpm, stdlib, the Playground, and the compiler landscape. Start here.
• The Fortran Package Manager (fpm) documentation (Tier 1). How to build, test, and add dependencies — the tool from Chapter 16 that makes an ecosystem possible.
• The Fortran stdlib documentation (Tier 1). The community standard library's module-by-module reference (stats, strings, sorting, special functions) — the "batteries" the language never shipped.
• The Fortran Playground (Tier 1). Run Fortran in your browser with nothing installed; the quickest way to try this chapter's snippets and settle a "what does it print?" question.

The process and community

• The J3 committee (j3-fortran.org) and its public repositories (Tier 1). Where the process in §39.2 actually happens: feature papers, meeting minutes, and the working drafts. Reading a live paper is the best way to understand how "I wish Fortran could…" becomes standard text — and how you could contribute.
• WG5 (the ISO working group) pages (Tier 1). The international body that sets each revision's scope and schedule; the place to see the plan for the standard after 2023.
• The Fortran Discourse (fortran-lang.discourse.group) (Tier 1, community). The active forum where users, compiler writers, and committee members discuss features, tooling, and the roadmap — the pulse of the "not dead" argument.

Compilers and their (changing) status

• The GCC/gfortran documentation and release notes (Tier 2 — dated). The authoritative, per-release word on which Fortran 2023 features your gfortran actually supports. Check the version you have before relying on conditional expressions, enumeration types, or typeof.
• LFortran project documentation (Tier 1 project; Tier 2 status). The interactive LLVM-based compiler of §39.3 — what it can do now, how to install it, and its honest, fast-moving support status.
• LLVM Flang documentation (Tier 1 project; Tier 2 status). The new production LLVM Fortran compiler maturing alongside gfortran and the vendor compilers (Intel ifx, NVIDIA nvfortran).

Suggested order

1. Skim fortran-lang.org and open the Playground; paste in this chapter's degree-trig snippet.
2. Read your gfortran release notes for its "Fortran 2023 status" — learn what you can compile today.
3. Browse one recent J3 paper on a feature you liked (say, conditional expressions) to see the process in action.
4. When you want the rigorous detail, go to Metcalf, Reid & Cohen and, for the exact wording, a working draft of the 2023 standard.
5. Follow the Fortran Discourse for a week — you will see the roadmap of §39.4 (generics, GPU) argued in real time, which is the most convincing evidence of a living language there is.