simon/jolt
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

seq fns are lazy by default, like Clojure (LazySeq, not eager-headed)

Browse source 
map/filter/remove/take/drop/concat/take-while/drop-while/mapcat/partition
built an eager-headed cseq: the first element (and the fn application) ran
at construction, so a side-effecting (map f coll) fired f immediately and
(class (map …)) was PersistentList instead of LazySeq. This diverged from
Clojure, which wraps the whole body in lazy-seq. It went unnoticed because
the conformance gate certifies values, not realization — eager and lazy
heads produce identical values — and unit.edn even baked PersistentList in
as expected. test.check's for-all-takes-multiple-expressions (which counts
side effects in a for-all body) exposed it.

Wrap each native producer's result in a lazy-seq node so the body, incl.
the first element, defers until forced — the forced cseq still has eager
heads, so reduce/count/dorun/etc. force on walk and there's no per-element
cost. dedupe's (seq coll) is moved inside its lazy-seq. A jolt LazySeq is
now recognized by coll?/empty, the analyzer's form predicates (a macro can
build its expansion with map), value-host-tags + instance? (LazySeq/ISeq/
Sequential), and reports clojure.lang.LazySeq.

Kept the native Scheme implementations rather than porting Clojure's: a
straight lazy-seq+cons port is 3x slower and Clojure's chunked fast path is
288x slower because jolt's chunk machinery is unoptimized (filed jolt-j9dz);
the wrapped natives are Clojure-lazy at native speed.

+12 corpus rows (laziness at construction, LazySeq type, both JVM-certified).
make test + shakesmoke green, selfhost holds, 0 new divergences.
This commit is contained in:
Yogthos 2026-06-28 00:16:47 -04:00
parent 92368b49f1
commit b879430618
10 changed files with 80 additions and 40 deletions
Download patch file Download diff file Expand all files Collapse all files

6
test/chez/unit.edn
View file

@ -475,10 +475,10 @@
{:suite "type" :expr "(type '(1 2))" :expected "clojure.lang.PersistentList"}
{:suite "type" :expr "(type '())" :expected "clojure.lang.PersistentList$EmptyList"}
{:suite "type" :expr "(type (first {:a 1}))" :expected "clojure.lang.PersistentVector"}
{:suite "type" :expr "(type (map inc [1 2]))" :expected "clojure.lang.PersistentList"}
{:suite "type" :expr "(type (filter odd? [1 2 3]))" :expected "clojure.lang.PersistentList"}
{:suite "type" :expr "(type (map inc [1 2]))" :expected "clojure.lang.LazySeq"}
{:suite "type" :expr "(type (filter odd? [1 2 3]))" :expected "clojure.lang.LazySeq"}
{:suite "type" :expr "(type (lazy-seq (cons 1 nil)))" :expected "clojure.lang.LazySeq"}
{:suite "type" :expr "(type (take 2 (iterate inc 0)))" :expected "clojure.lang.PersistentList"}
{:suite "type" :expr "(type (take 2 (iterate inc 0)))" :expected "clojure.lang.LazySeq"}
{:suite "type" :expr "(type inc)" :expected "clojure.core$inc"}
{:suite "type" :expr "(type (sorted-map :a 1))" :expected ":map"}
{:suite "type" :expr "(type (sorted-set 1))" :expected ":jolt/sorted-set"}