Compiler research (#10)

adds self-hosted compiler is functionally:
 
- The default compile path is the portable pipeline using jolt.analyzer (Clojure) → host-neutral IR → backend.janet.
- The analyzer is itself Clojure, compiled by jolt for true self-hosting.
- bootstrap-fixpoint passes (stage1 == stage2 == stage3): rebuilding the compiler on its own output.
- clojure.core is now self-hosted in the overlay.
- Stateful forms (defmacro/ns/deftype/defmulti/require/in-ns) are interpreted by design.

jolt-core/clojure/core/40-lazy.clj

@@ -0,0 +1,100 @@
+;; clojure.core — lazy tier. Canonical CLJS-based lazy seq fns.
+;; Loaded after 30-macros.clj, so lazy-seq macro is available.
+;;
+;; Each fn ported from CLJS core.cljs, stripped of chunked-seq branches.
+
+;; --- distinct ---
+(defn distinct [coll]
+  (let [step (fn step [xs seen]
+               (lazy-seq
+                 ((fn [[f :as xs] seen]
+                    (when-let [s (seq xs)]
+                      (if (contains? seen f)
+                        (recur (rest s) seen)
+                        (cons f (step (rest s) (conj seen f))))))
+                   xs seen)))]
+    (step coll #{})))
+
+
+;; --- keep ---
+(defn keep
+  ([f]
+   (fn [rf]
+     (fn ([] (rf)) ([result] (rf result))
+       ([result input]
+        (let [v (f input)]
+          (if (nil? v) result (rf result v)))))))
+  ([f coll]
+   (lazy-seq
+    (when-let [s (seq coll)]
+      (let [x (f (first s))]
+        (if (nil? x)
+          (keep f (rest s))
+          (cons x (keep f (rest s)))))))))
+
+;; --- keep-indexed ---
+(defn keep-indexed
+  ([f]
+   (fn [rf]
+     (let [ia (volatile! -1)]
+       (fn ([] (rf)) ([result] (rf result))
+         ([result input]
+          (let [i (vswap! ia inc)
+                v (f i input)]
+            (if (nil? v) result (rf result v))))))))
+  ([f coll]
+   (letfn [(keepi [idx coll]
+             (lazy-seq
+               (when-let [s (seq coll)]
+                 (let [x (f idx (first s))]
+                   (if (nil? x)
+                     (keepi (inc idx) (rest s))
+                     (cons x (keepi (inc idx) (rest s))))))))]
+     (keepi 0 coll))))
+
+;; --- map-indexed ---
+(defn map-indexed
+  ([f]
+   (fn [rf]
+     (let [i (volatile! -1)]
+       (fn ([] (rf)) ([result] (rf result))
+         ([result input] (rf result (f (vswap! i inc) input)))))))
+  ([f coll]
+   (letfn [(mapi [idx coll]
+             (lazy-seq
+               (when-let [s (seq coll)]
+                 (cons (f idx (first s)) (mapi (inc idx) (rest s))))))]
+     (mapi 0 coll))))
+
+;; --- cycle ---
+(defn cycle [coll]
+  (if-let [vals (seq coll)]
+    (let [n (count vals)]
+      (letfn [(cstep [i]
+                (lazy-seq
+                  (cons (nth vals (mod i n)) (cstep (inc i)))))]
+        (cstep 0)))
+    ()))
+
+;; --- repeatedly ---
+(defn repeatedly
+  ([f] (lazy-seq (cons (f) (repeatedly f))))
+  ([n f] (take n (repeatedly f))))
+
+;; --- repeat ---
+(defn repeat
+  ([x] (lazy-seq (cons x (repeat x))))
+  ([n x] (take n (repeat x))))
+
+;; --- iterate ---
+(defn iterate [f x]
+  (lazy-seq (cons x (iterate f (f x)))))
+
+
+;; --- partition-all ---
+(defn partition-all
+  ([n coll] (partition-all n n coll))
+  ([n step coll]
+   (lazy-seq
+    (when-let [s (seq coll)]
+      (cons (take n s) (partition-all n step (nthrest coll step)))))))