Joseph Ferano
a4c6b996ff
The trio the author decided on 2026-09-20 is now all built: def is CL's defparameter — its initialiser runs on every daemon re-run, unguarded, so an edited initialiser repaints the same storage on C-c C-c plus re-run — defonce (Clojure's name for CL's defvar, per the author) initialises once behind the .init~once. flag, and defconst stays the image. One parse arm reads both forms; the difference is Ast.reinit, carried to Tast.global's grerun. Emit.startup_plan gives a def no guard flag, and Check.check_global lifts every def initialiser — zero and literal included — into global/<n>, so the host's startup reaches it through the function cell and a re-evaluated def swaps it (Session's def_inits; Emit.redefinition declares the cell for a non-sibling target). The old defvar spelling is refused with the rename and both compiling spellings, and every program, test, doc and editor list is swept — except sand.flan, the author's live WIP, whose seven defvar lines are flagged in FIX.org and keep its three dependent tests red on this branch.
104 lines
4.5 KiB
Plaintext
104 lines
4.5 KiB
Plaintext
;;;; slurp and barf — NEXT.md decisions 2 and 5.
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;;;;
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;;;; slurp reads a whole file and answers a (Vec u8). It allocates, which is
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;;;; why it waited for Vec, and it follows spec-memory.md's rule to the letter:
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;;;; no allocating operation returns an error, so there is no Result here and
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;;;; no out-parameter anywhere.
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;;;;
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;;;; Failure signals a condition under a restart, which is the pattern
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;;;; StorageExhausted set this session. Two restarts, and they are the pair
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;;;; Common Lisp establishes for a file-error:
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;;;;
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;;;; retry the file may be there now
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;;;; use-value [p string] try this other path instead
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;;;;
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;;;; use-value is a *typed* restart — the second thing this session bought —
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;;;; and it is the first one the compiler itself emits. Its parameter is the
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;;;; path slot the attempt reads, so the clause body is empty: the invoker's
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;;;; argument lands in the slot, the clause falls through, and the loop
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;;;; re-attempts against the new path.
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;; Handlers cannot see the locals of the function that established them, so the
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;; observations are globals — the same shape exhausted.flan uses.
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(defonce seen i64)
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(defonce last-reason i32)
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(defonce last-op i32)
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(defonce last-path string)
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(defn main [] i32
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;; ── The happy path ────────────────────────────────────────────────
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(let [v (slurp "programs/assets/a.txt")]
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(println (len v)) ; 13
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(print (string (as-slice v))) ; hello from a
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(free v))
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;; Byte-exact, the same as an embed: nothing here decodes anything.
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(let [v (slurp "programs/assets/raw.bin")]
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(println (len v)) ; 4
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(println (at v 0)) ; 0
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(println (at v 2)) ; 255
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(free v))
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;; ── use-value: a missing file, answered with another path ─────────
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;; The textbook case. The handler does not know what slurp was going to do
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;; with the bytes and does not have to: it names a file that is there and
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;; the read resumes as if that had been asked for all along.
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(handler-bind
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[(FileError [c]
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(set seen (+ seen 1))
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(set last-reason (.reason c))
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(set last-op (.op c))
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(set last-path (.path c))
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(invoke-restart 'use-value "programs/assets/b.bin"))]
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(let [v (slurp "programs/assets/does-not-exist")]
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(println (len v)) ; 3
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(println (string (as-slice v))) ; BBB
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(free v)))
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(println seen) ; 1
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(println (= last-reason file-missing)) ; true
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(println (= last-op file-op-read)) ; true
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;; The condition carries the path that actually failed, not the one that
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;; eventually worked — the handler is told what it is answering about.
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(println last-path) ; programs/assets/does-not-exist
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;; ── barf, and reading back what it wrote ──────────────────────────
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(barf "slurp-out.txt" (bytes-view "round trip\n"))
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(let [v (slurp "slurp-out.txt")]
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(println (len v)) ; 11
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(print (string (as-slice v))) ; round trip
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(free v))
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;; barf's own failure signals the same condition with op = write. A directory
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;; that does not exist is the reachable case on every platform.
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(set seen 0)
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(handler-bind
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[(FileError [c]
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(set seen (+ seen 1))
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(set last-op (.op c))
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(invoke-restart 'use-value "slurp-out.txt"))]
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(barf "no-such-dir/x.txt" (bytes-view "second\n")))
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(println seen) ; 1
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(println (= last-op file-op-write)) ; true
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(let [v (slurp "slurp-out.txt")]
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(print (string (as-slice v))) ; second
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(free v))
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;; ── retry: the file was not there, so the handler makes it ────────
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;; The other restart, and the one use-value cannot stand in for: here the
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;; path is right and the world is wrong. The handler fixes the world and
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;; re-attempts the *same* request, which is exactly what retry means for a
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;; failed allocation too.
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(set seen 0)
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(handler-bind
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[(FileError [c]
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(set seen (+ seen 1))
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(set last-reason (.reason c))
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(barf "slurp-made.txt" (bytes-view "made by the handler\n"))
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(invoke-restart 'retry))]
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(let [v (slurp "slurp-made.txt")]
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(print (string (as-slice v))) ; made by the handler
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(free v)))
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(println seen) ; 1
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(println (= last-reason file-missing)) ; true
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0)
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