jerboa-compat

Gerbil-only compatibility shims providing the parts of Jerboa's standard library that Gerbil Scheme lacks, so Jerboa .ss sources (e.g. from jerboa-emacs) can be ported to Gerbil (e.g. gerbil-emacs) with mechanical import renames instead of rewrites.

Repo routing: this is a Gerbil library, so it lives on git.cons.io as gerbil-jerboa-compat (Gerbil package name: jerboa-compat). The on-disk dir is ~/mine/jerboa-compat.

Why

jerboa-emacs and gerbil-emacs are forks of one ancestor and share almost the same surface syntax (def, defstruct, :std/sugar, [...], (export …)). The friction when porting Jerboa → Gerbil is a handful of stdlib modules Jerboa exposes that Gerbil does not — concentrated in jerboa-emacs's chez-powers.ss. This package reproduces that surface on stock Gerbil.

Modules

Module	Backing	Notes
:jerboa-compat/atom	native	Clojure-style atoms; was already portable Gerbil.
:jerboa-compat/lru-cache	native	Gerbil has :std/misc/lru with a different API; this gives Jerboa's lru-cache-* surface, thread-safe.
:jerboa-compat/stm	native	Gerbil has no :std/stm. STM on Gambit threads + condition variables (the fiber path is dropped).
:jerboa-compat/engine	native	Gerbil has no :std/engine (Chez make-engine has no Gambit analog). Arbitrary-thunk engines and timed-eval fail closed because lexical closures cannot cross exec safely; timed-eval/cooperative is available for trusted cleanup-aware work.

timed-eval/cooperative thunks can poll (engine-cancelled?) and unwind normally when their budget expires; the helper performs a mandatory join so dynamic-wind cleanup completes. The default timed-eval, fuel-eval, and engine APIs reject arbitrary thunks. Production callers needing hostile-code isolation must define a bounded data protocol and launch a fresh executable; raw-fork callbacks are not a supported substitute. | :jerboa-compat/powers | umbrella | Mirrors chez-powers.ss: re-exports the four above plus :std/amb, :std/misc/{completion,rwlock,pqueue,wg,channel,rbtree,barrier}, with Jerboa-named adapters where Gerbil's names differ. |

Porting import map

When converting a jerboa-emacs source to gerbil-emacs:

Jerboa import	Gerbil import
:jerboa-emacs/chez-powers	:jerboa-compat/powers
:jerboa-emacs/atom	:jerboa-compat/atom
:jerboa-emacs/<other>	:gemacs/<other>
:jerboa-scintilla/…	:gerbil-scintilla/…
:jerboa-qt/…	:gerbil-qt/…

(The jerboa-gerbil converter applies these automatically.)

Residual gaps

A few Jerboa symbols can't be backed by Gerbil's primitive without a native rewrite; they are not yet exported by powers.ss:

• channel-length, channel-empty?, channel-select — Gerbil's :std/misc/channel is otherwise re-exported (put/get/try/close/closed?).
• barrier-parties, barrier-waiting, barrier-reset! — Gerbil's barrier is one-shot (post/error/wait), not the cyclic N-party barrier Jerboa ships.
• amb is re-exported from :std/amb; confirm call sites (its dynamic-state macros differ subtly from Jerboa's).

Each is a small follow-up (a native ring-buffer channel and a cyclic barrier).

Build & test

gerbil build          # or ./build.ss

Modules are developed and tested through the gerbil-mcp toolchain (gerbil_compile_check, gerbil_eval) against /opt/gerbil/bin/gxi.