a6f0f8a6fe
Continue the kernel shrink. last/butlast become canonical Clojure defs (pure first/next/loop/recur) in the core.clj overlay, dropping two realize-for-iteration uses from the Janet kernel. second was the obvious next candidate but can't move: the self-hosted compiler front-end (analyzer.clj) calls it, and the compiler has to compile the overlay, so anything it uses must already exist as a Janet primitive. Documented that as a third clause of the safe-to-move rule. Suite green, clojure-test-suite battery holds 3913 pass / 58 clean, binary builds and runs the embedded overlay.
31 lines
1.5 KiB
Clojure
31 lines
1.5 KiB
Clojure
;; The Clojure portion of clojure.core. Loaded into the clojure.core namespace at
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;; init (api/init), AFTER the Janet primitives are interned by core/init-core!,
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;; and compiled by the self-hosted pipeline (analyzer -> IR -> Janet back end).
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;;
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;; This is the Phase 4 kernel-shrink seam: fns expressible in plain Clojure on top
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;; of the remaining Janet primitives move here from core.janet, one at a time,
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;; each compiled by the prior stage. Anything here must depend only on core vars
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;; already interned by init-core! (and on other overlay fns defined above it).
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;;
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;; Safe-to-move rule: a fn can move here only if it is (1) NOT in
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;; compiler/core-renames (that map emits core-X Janet symbols directly), (2) has
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;; no internal Janet callers of its core-X binding, and (3) is NOT used by the
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;; self-hosted compiler itself (jolt-core/jolt/*.clj) — the compiler has to
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;; compile this overlay, so anything it calls must already exist as a Janet
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;; primitive. (That last rule is why `second`, used by analyzer.clj, stays in
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;; Janet even though it has no Janet callers.)
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(defn ffirst [coll] (first (first coll)))
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(defn nfirst [coll] (next (first coll)))
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(defn fnext [coll] (first (next coll)))
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(defn nnext [coll] (next (next coll)))
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;; Canonical Clojure defs: pure first/next/loop/recur, no Janet realize-for-iteration.
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(defn last [s]
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(if (next s) (recur (next s)) (first s)))
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(defn butlast [s]
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(loop [ret [] s s]
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(if (next s)
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(recur (conj ret (first s)) (next s))
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(seq ret))))
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