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.
62 lines
2.6 KiB
Plaintext
62 lines
2.6 KiB
Plaintext
;;;; (slice-from-ptr p n) — NEXT.md, "a pointer from C needs a length before it
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;;;; can be indexed". The motivating pointers come from C, but nothing about
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;;;; the form does: a (Ptr T) is a (Ptr T) whoever made it, so this case makes
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;;;; its own with (addr (at a 0)) and needs no library and no window.
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;;;;
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;;;; What is asserted, line by line:
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;;;;
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;;;; - the length is the one the caller stated, and (len s) answers it;
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;;;; - the elements read through are the same storage, not a copy — the last
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;;;; two lines write through the slice and read the array back, which is
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;;;; the whole ptr+len claim;
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;;;; - a shorter promise than the truth is legal and is what indexing then
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;;;; believes, because the caller's number is the only length there is;
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;;;; - the result is an ordinary [T]: it slices, it is passed to a function
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;;;; that takes a slice, and the prelude's algorithms work on it.
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;;;;
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;;;; What is NOT here, and is in test_flan.ml's refusal table instead: a
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;;;; negative literal length, a first argument that is not a pointer, and
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;;;; (free (slice-from-ptr ...)) — a slice owns nothing, so free refuses it by
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;;;; the rule it already had.
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(defonce a [5 i32])
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(defn total [s [i32]] i32
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(let [acc 0]
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(dotimes [i (len s)]
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(set acc (+ acc (at s i))))
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acc))
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(defn main [] ()
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(dotimes [i 5]
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(set (at a i) (* (+ i 1) 10)))
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;; The whole array, as the caller promises it: five elements behind the
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;; address of the first.
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(let [s (slice-from-ptr (addr (at a 0)) 5)]
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(println (len s)) ; 5
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(println (at s 0)) ; 10
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(println (at s 4)) ; 50
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(println (total s)) ; 150
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;; An ordinary [i32] from here on: slice it, and the sub-view still points
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;; into the same storage.
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(println (total (slice s 1 3)))) ; 50
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;; A promise shorter than the truth. Nothing complains — there is nothing to
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;; complain with — and the length the caller gave is the length indexing and
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;; the bounds check both use.
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(let [s (slice-from-ptr (addr (at a 1)) 2)]
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(println (len s)) ; 2
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(println (total s))) ; 50
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;; Zero is a length like any other. An empty slice is not a null pointer and
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;; is not an error.
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(println (len (slice-from-ptr (addr (at a 0)) 0))) ; 0
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;; It is a view, not a copy: a write through the slice is a write to the
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;; array, and this is what would fail if the form ever grew a memcpy.
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(let [s (slice-from-ptr (addr (at a 0)) 5)]
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(set (at s 2) 7)
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(println (at a 2)) ; 7
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(println (total s)))) ; 127
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