Autoconf syntax is surprisingly lispy. AC_DEFUN and AC_DEFSUBST seem very similar to lisp's defun and defsubst.
miniblog.
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Historical defsubst macrology by jwz before the elisp byte compiler: https://web.mit.edu/~deberg/emacs/elisp/defsubst.el (cf #define in C!)
Trying to optimise some CPU-bound elisp. Favouring C built-ins makes a big difference! Next, I'm going to try byte-compiling and defsubst.