Zoë Trout's favorites at wedgewack.org/ursa.lisp.txt are Common Lisp:
iterative LOOP macros, setf cascades, defun with &optional, image-
based stone-lisp culture. Her first contribution to lumbda was a
question — "do we care for our programs, and how long are they alive
for?" — and the answer now extends beyond the RNG portal (§7.5) to
iteration style itself.
Four-phase delivery, all under ticket 0004:
Phase A — idiomatic Scheme ports at examples/ursa-scheme.lsp.
Every Zoë defun rewritten as named-let + tail recursion + list-
backed work queue + type-predicate dispatch.
Phase B — CL compat shim at cl-compat.lsp.
defun (with &optional), setf (simple vars, multi-pair), flet,
multiple-value-bind, t / nil (nil=#f so cond/if compose),
evenp/oddp/plusp/minusp/zerop, mod/ash/logbitp/nreverse,
cl-when/cl-unless (plain when is a void-returning lumbda special
form), declare (no-op), cddddr (missing accessor).
Phase C — cl-loop macro covering 14 patterns.
while/until/repeat, for VAR from A to/below/downto B, for VAR =
INIT [then STEP], for VAR across VEC, of-type T, do, when/unless
return, finally (return VAL). Sequential do*-style stepping via
gensym + cl-subst. Look-ahead termination so `repeat 4 for s = 4
then (- (* s s) 2) finally (return s)` returns 37634 (pre-step)
rather than 1416317954 (post-step). Every expansion ends in a
named-let tail call — TCO holds for loops of any length.
Phase D — load examples/ursa.lisp.txt with minimal annotation.
Preserves Zoë's CL. Minimal edits documented in file header:
load cl-compat.lsp, loop→cl-loop, when→cl-when, random→random-int,
&key→&optional. rho/digits omitted (need make-array/CLOS — see
ticket 0004 for scope boundary).
Defect uncovered along the way (c/types.c env_lookup): a "global
shortcut" checked global env immediately after missing the local
frame, SKIPPING intermediate parent scopes. Broke lexical scoping
whenever a parent scope shadowed a global. Reproduced with
(define s 4)
(let ((s 100)) (let ((m 0)) s)) ; returned 4, should return 100
Any nested let whose body referenced a shadowed name silently read
the global. Fix: remove the shortcut, walk the parent chain end-to-
end. 1255 assertions across five suites pass unchanged after fix —
surfaced only because cl-loop iterator names routinely collide with
globals accumulated in a stone-lisp image.
Whitepaper §9.2 documents the CL-in-Scheme design and the guarantees
that survive (TCO, portal determinism, cross-impl reproducibility).
Zoë added to authors + acknowledgments; reacknowledgment reframes
her first contribution as the deeper program-lifetime question, with
RNG portal as a derivative (§7.5) and cl-loop as the follow-up.
Tests: tests/cl-compat.lsp (44 assertions) and tests/ursa.lsp (28
assertions) exercise both paths under Python + C via tests/zoe-
favorites-test.sh, wired into make test-all.
MOAD notes: unmoad flags memq/assq in cl-compat.lsp over cl-loop-
keywords (~30 elements, constant) and var->new (≤4 state vars per
loop). Both are macro-expansion-time, bounded-small-N — not runtime
hot paths. Pre-existing c/types.c findings (strcmp-in-loop for
record-type lookup) are not from this change.
russell@unturf.com
192118388f