https://github.com/aiez/lithp

lithp is less library: the smallest set of Common Lisp add-ons that measurably shrinks application code — five plain constructs plus a handful of utilities, ~130 lines total, no reader macros, no dependencies. Found by ablation: we wrote the same machine-learner four ways and kept only what paid rent. The why, the data, and the style rules are in blog.md — this file is just the manual.

git clone https://github.com/aiez/optimiz # access test data
git clone https://github.com/aiez/lithp && cd lithp
sbcl --script fft.lisp          # the sweet-spot version
sbcl --script fft.lisp --trees  # show all grown trees
sbcl --script fft.lisp --grows  # timing benchmark

Sections: NAME | SYNOPSIS | KIT | UTILITIES | FILES | LICENSE

Files: lithp.lisp | blog.md | fft.lisp | small.lisp | to_small.lisp | yuck.lisp | tiny.lisp | tiny.vim | Makefile

NAME

lithp — less library: the pay-rent subset (130 lines, no deps)

SYNOPSIS

(load "lithp.lisp")
(defvar *settings* '((seed . 1234567891) (file . "data.csv")))
(defmacro my (k) `(cdr (assoc ',k *settings*)))
(cli *settings*)                ; -s 42 on argv updates seed
(setf *seed* (my seed))

THE KIT (five constructs)

form	meaning
(fn expr)	variadic lambda; refer to args as $1..$9 as used
(? x a b)	quoted-key chained access: (ats (ats x 'a) 'b)
(let+ (...) ...)	one binder: (x 1) let, ((a b) lst) destructure, (f (z) ...) local fn
(o 'k1 v1 'k2 v2)	build equal-hash record
(ats x k)	read hash or struct slot uniformly; setf-able

Plus (keys h) — list of hash keys.

UTILITIES

group	functions
print	(cat ...) strings together; (prn fmt args...) format + newline
pick	(least lst f) / (most lst f) — min/max by key fn
parse	(thing s) string→number/symbol; (cells s) split csv line; (csv file) rows of things
cli	(args) argv; (cli alist) -x val sets first-char-matching key
random	(rand n) (rint n) (shuffle lst) (few lst n) — seeded Park-Miller (*seed*), reproducible across languages

FILES

file	what
lithp.lisp	this library
blog.md	the ablation study: why these and only these
yuck.lisp	naive CLOS port, 605 lines — the cautionary tale
small.lisp	plain ANSI CL, design only, 261 lines
fft.lisp	+ the kit, 240 lines — the sweet spot
to_small.lisp	+ reader macros via tiny.lisp, 214 lines — fun, not leverage
tiny.lisp / tiny.vim	the full dialect and its required editor support

All four programs (fft, small, to_small, yuck) produce byte-identical output (same seeded RNG as the Python original they port).

LICENSE

MIT. (c) 2026 Tim Menzies, timm@ieee.org