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.
71 lines
2.7 KiB
Plaintext
71 lines
2.7 KiB
Plaintext
;;;; Dyn maps and keywords: the literal, the operations, the printing, and a
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;;;; collection loop that outruns the GC floor.
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;;;;
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;;;; Every value here is dyn. {:a 1} is a heap map the collector traces; :a is
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;;;; an interned keyword, so two spellings of one name are the same word and
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;;;; equality never reads the bytes; [1 2] where a dyn is wanted is the
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;;;; runtime's own vec. The printed forms are the dyn renderer's — a space
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;;;; before every element, strings quoted when nested — pinned here across
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;;;; both backends the way test/dyn_ops.c pins them from C.
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;; A dyn global: rooted once at startup, so what main stores in it survives
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;; every collection the churn loop below causes.
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(defonce config dyn)
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(defn main [] i32
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;; The literal, and what it prints as.
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(let [m {:a 1 :b "two" :xs [1 2 3] :inner {:c 2.5}}]
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(println m)
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(println (length m))
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(println (get m :a))
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(println (get m :b))
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(println (get m :xs))
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(println (get (get m :inner) :c))
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;; Absence is nil — an answer, not a trap — and has-key? is the question
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;; that stays askable when nil might also be stored.
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(println (get m :missing))
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(println (= (get m :missing) nil))
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(println (has-key? m :a))
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(println (has-key? m :missing))
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(put m :flag nil)
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(println (get m :flag))
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(println (has-key? m :flag))
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;; put replaces an equal key's value in place; the length holds still.
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(put m :a 99)
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(println (get m :a))
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(println (length m))
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;; Keywords: identity equality, printing, and the runtime constructor —
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;; (keyword "a") has to be the same word as the literal :a.
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(println (= :a :a))
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(println (= :a :b))
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(println (= :a "a"))
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(println (= (keyword "a") :a))
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(println :standalone)
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;; Keys are whole values compared structurally: a text and a keyword are
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;; two keys, and a vec of numbers can key a map.
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(put m "a" "text key")
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(println (length m))
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(println (get m "a"))
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(put m [1 2] "vec key")
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(println (get m [1 2]))
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;; Maps compare structurally, by lookup and not by insertion order.
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(println (= {:x 1 :y 2} {:y 2 :x 1}))
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(println (= {:x 1} {:x 2}))
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(println (= {:x 1} {:x 1 :y 2})))
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;; The churn: enough map, vec and text allocation to pass the 1 MiB floor
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;; many times over, against one live map held in a rooted global. A marker
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;; that lost track of a map's keys or values frees something live, and the
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;; sum at the end comes out wrong — or ASan speaks, in the sanitize sweep.
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(set config {:total 0})
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(dotimes [i 200000]
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(let [row {:i 1 :s "forty-seven bytes of text to fatten each row" :v [1 2 3]}]
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(put config :total (+ (get config :total) (length row)))))
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(println (get config :total))
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0)
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