Joseph Ferano
d6fc15474b
The author: "I think I prefer length over len, because then I'll use len as the variable name". One arm in check.ml, one row in the table beside it, and every (len x) in lib, test, examples, vendor, spike, docs, web, emacs, plan.org and NEXT.md rewritten. Shadowing and builtin/ had already taken most of the sting out: a (defn len ...) was legal and won in its own file, and builtin/len reached past it. What was left is that len was still a builtin — the defn earned a warning, and a wrapper had to say builtin/ at every inner call. Now there is nothing under the short name: len is an ordinary identifier in every position, which is what (let [len (length xs)] ...) wants. length takes over as shadowing's worked example rather than the feature losing one. shadow-builtin.flan, builtin-qualified.flan, pkgs/shadowed and the builtin/ rows in test_flan move to it and go on testing shadowing. A call to a len nothing defines is answered where an unknown function is, after every table and after the shadowing guard, so a program with its own len never reaches it. The sentence is said rather than guessed at — len and length are three edits apart and the did-you-mean's net is one — and the call is written back out through spell_arg, as-slice's spelling lifted out of it and now shared, so what is printed compiles. sand.flan:33 still calls the old name and is the author's to change; until it does, test_acceptance and test_session abort there. Both were run green against a copy with that one line changed. FIX.org says so.
122 lines
5.5 KiB
Plaintext
122 lines
5.5 KiB
Plaintext
;;;; (map-remove m k) — the operation a Map has been missing.
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;;;;
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;;;; Removal is the one map operation that can break the *other* ones: Robin
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;;;; Hood lookups stop at the first empty slot, so a hole punched in the middle
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;;;; of a probe run hides every entry after it, and the entries it hides are
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;;;; found by no test that only removes and asks about what it removed. So the
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;;;; rows below are mostly about the survivors.
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;;;;
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;;;; Odin marks a tombstone and repairs on the next insert; this shifts the run
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;;;; back and stays tombstone-free, which is the arrangement the rest of the
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;;;; file already assumed. A version that punched the hole and left it passes
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;;;; row 1 and fails row 3.
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(defstruct Cell [x i32 y i32])
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(defn main [] i32
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;; (1) The value comes back, the length drops, and the key is gone. An
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;; absent key is None and changes nothing — the same answer get gives, since
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;; a key that was not there is an answer and not a failure.
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(let [m (map-new i32 i64)]
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(put m 1 100)
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(put m 2 200)
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(match (map-remove m 1)
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(Some v) (do (print v) (println "")) ; 100
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None (println "missing"))
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(print (length m)) (println "") ; 1
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(print (has-key? m 1)) (println "") ; false
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(match (map-remove m 1) (Some v) (do (print v) (println "")) None (println "gone"))
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(println (length m)) ; gone, then 1
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(free m))
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;; (2) Removing every entry empties the map, and it is usable afterwards:
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;; the block is still there and the slots are empty rather than poisoned.
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(let [m (map-new i32 i32)]
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(dotimes [i 64] (put m i i))
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(dotimes [i 64] (map-remove m i))
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(print (length m)) (println "") ; 0
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(put m 7 77)
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(match (get m 7) (Some v) (do (print v) (println "")) None (println "?")) ; 77
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(print (length m)) (println "") ; 1
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(free m))
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;; (3) The survivors, which is the row that matters. 2000 entries is eight
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;; grows, so the runs are long and interleaved; removing the even keys and
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;; then asking after every odd one is asking whether any probe run was cut.
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;; A backward shift that stopped one slot early loses entries here and
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;; nowhere else.
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(let [m (map-new i32 i64)]
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(dotimes [i 2000] (put m i (* (i64 i) 3)))
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(let [taken 0]
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(dotimes [i 2000]
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(if (= 0 (% i 2))
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(match (map-remove m i)
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(Some v) (if (= v (* (i64 i) 3)) (set taken (+ taken 1)))
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None (set taken taken))))
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(print taken) (println "")) ; 1000
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(print (length m)) (println "") ; 1000
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(let [lost 0 ghosts 0]
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(dotimes [i 2000]
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(match (get m i)
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(Some v) (if (or (= 0 (% i 2)) (not (= v (* (i64 i) 3))))
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(set ghosts (+ ghosts 1)))
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None (if (not (= 0 (% i 2))) (set lost (+ lost 1)))))
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(print lost) (println "") ; 0
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(print ghosts) (println "")) ; 0
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;; Re-inserting what was taken out puts the length back, through no grow:
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;; the block still has the room the removals freed up.
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(dotimes [i 2000] (if (= 0 (% i 2)) (put m i (* (i64 i) 3))))
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(print (length m)) (println "") ; 2000
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(free m))
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;; (4) A struct key and a string key, so the emitted hash/equality pair is
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;; on the removal path too and not only on get's.
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(let [g (map-new Cell i32)]
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(dotimes [i 20] (dotimes [j 20] (put g (Cell {.x i .y j}) (+ (* i 100) j))))
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(match (map-remove g (Cell {.x 7 .y 9}))
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(Some v) (do (print v) (println "")) ; 709
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None (println "?"))
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(print (has-key? g (Cell {.x 7 .y 9}))) (println "") ; false
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(print (has-key? g (Cell {.x 7 .y 10}))) (println "") ; true
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(print (length g)) (println "") ; 399
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(free g))
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(let [s (map-new string i32)]
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(put s "alpha" 1)
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(put s "beta" 2)
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(match (map-remove s "alpha")
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(Some v) (do (print v) (println "")) ; 1
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None (println "?"))
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(print (has-key? s "beta")) (println "") ; true
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(print (length s)) (println "") ; 1
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(free s))
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;; (5) Iteration after removals answers exactly the survivors. The cursor is
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;; started fresh — a cursor held *across* a removal is invalidated by the
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;; shift, the same way a put that grows invalidates one.
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(let [m (map-new i32 i32)]
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(dotimes [i 100] (put m i i))
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(dotimes [i 100] (if (= 0 (% i 3)) (map-remove m i)))
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(let [cur (i64 0) k 0 v 0 seen 0 sum 0]
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(while (map-next m (addr cur) (addr k) (addr v))
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(set seen (+ seen 1))
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(if (not (= k v)) (set sum (+ sum 1))))
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(print seen) (println "") ; 66
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(print sum) (println "")) ; 0
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(print (length m)) (println "") ; 66
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(free m))
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;; (6) An arena, which refuses can-free. Removal asks the allocator for
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;; nothing and hands it back nothing — a key and a value live inside the one
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;; block the map allocated — so it means here exactly what it means on the
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;; heap, and the region is released whole as always.
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(let [ar (arena-new 1048576)]
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(with-allocator ar
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(let [t (map-new i32 i32)]
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(dotimes [i 300] (put t i (* i 2)))
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(dotimes [i 300] (if (= 0 (% i 2)) (map-remove t i)))
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(print (length t)) (println "") ; 150
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(match (get t 299) (Some v) (do (print v) (println "")) None (println "?")) ; 598
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(print (has-key? t 298)) (println ""))) ; false
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(free-all ar))
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0)
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