Coding Style

The code mostly adheres to the Google C++ Style guide, with a few key exceptions:

Compile against C++20. Since we support both gcc and clang (Emscripten), some esoteric features of C++20 still can't be used yet. We don't use modules (yet) because of poor tooling support, but we'd like to.
Use exceptions instead of error codes or rogue return values. It's ok to just crash when there's a problem.
Use snake_case for names. Type names (classes, class templates, aliases) use Stroustrup_case, so that we can immediately recognize types by the uppercase first letter. Note: some variables use an uppercase letter when it's a useful math symbol or initials, e.g., X, Ttwiddle.
Use (Almost-Always-Auto (AAA) style)[https://herbsutter.com/2013/08/12/gotw-94-solution-aaa-style-almost-always-auto/] for variable and function declarations, e.g., auto double(int x) -> int; and auto m = node.mutations();
[TO ENFORCE] Prefer not to ! in Boolean expressions.
[TO ENFORCE] We use log to mean "log base e", never ln
[TO ENFORCE] We use west-coast const style, and pointer and reference indicators (* and &) go with the types, not the names, e.g., const char* str instead of char const *str.
[TO ENFORCE] Use std::ssize(c) (signed) instead of c.size() (unsigned) to avoid pitfalls of mixing signed and unsigned quantities in arithmetic
[TO ENFORCE] Prefer absl::flat_hash_map and absl::flat_hash_set to std::unordered_map and stl::unordered_set
[TO ENFORCE] Prefer structs with public fields to classes with private fields and accessors (see C++ Core Guideline C.131).

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