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.
113 lines
4.3 KiB
Plaintext
113 lines
4.3 KiB
Plaintext
;;;; A generic body that allocates a container of its own element type.
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;;;;
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;;;; The caller-allocated spelling — the caller passes a destination slice and
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;;;; the callee fills it — is the one a generic could always write. This is the
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;;;; other half: [sorted] below asks for the storage itself, at whatever type
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;;;; the instantiation turned out to be, and hands the container back.
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;;;;
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;;;; What makes that work is that a type variable names a type wherever a type
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;;;; name goes, in both spellings: [$t] is how a defn signature introduces the
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;;;; variable and [t] is how the body spells the same one, and the constructors
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;;;; that read a type argument — vec-new, map-new, array, a cast — accept
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;;;; either. The size and the alignment flan_vec_init is given are produced
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;;;; from the element type at the point the copy is checked, so each copy
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;;;; carries its own: 4 and 4 in the i32 one, 8 and 8 in the f64 one. The
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;;;; abstract pass, which checks the body once with nothing substituted, is
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;;;; never emitted, so no copy ever asks for the size of a variable.
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;; The motivating case: allocate, fill, sort, return. Two element types below,
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;; so there are two copies and the storage in each is the instantiation's.
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(defn sorted [xs [$t]] (Vec $t)
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{:where (ordered? $t)}
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(let [v (vec-new $t)]
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(dotimes [i (length xs)] (push v (at xs i)))
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(sort (slice v))
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v))
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;; The same, against a named allocator rather than the context's. Both arities
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;; read their element type the same way, so both take a variable.
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(defn sorted-in [xs [$t] al Allocator] (Vec $t)
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{:where (ordered? $t)}
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(let [v (vec-new $t al)]
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(dotimes [i (length xs)] (push v (at xs i)))
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(sort (slice v))
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v))
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;; A Map whose key is the variable. The predicate is what lets the hash and the
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;; equality be deferred to the copy; see generics.flan for that half.
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(defn distinct-count [ks [$k]] i32
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{:where (hashable? $k)}
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(let [m (map-new $k i32)]
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(dotimes [i (length ks)]
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(put m (at ks i) 1))
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(let [n (length m)] (free m) n)))
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;; The zeroed fixed array. Its length is still a compile-time constant; only
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;; the element type is the variable, and that is answered per copy.
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(defn middle-of [x $t] $t
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(let [a (array 3 $t)]
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(set (at a 1) x)
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(at a 1)))
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;; A cast to the variable, written with the sigil.
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(defn widen [x i32 d $t] $t
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{:where (numeric? $t)}
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(do d ($t x)))
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;; There is no row here for a type variable that instantiates at dyn: a
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;; generic is not instantiated at dyn at all, and the refusal says to reach
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;; for the dyn side instead. So nothing a copy of one of these bodies does
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;; can reach the dyn container.
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;; Allocation failure inside a generic copy, handled the way exhausted.flan
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;; handles it: a ceiling, a handler that raises it, and retry re-attempting the
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;; request that did not fit. The globals are because a handler cannot see the
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;; locals of the function that established it.
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(defonce tight Allocator)
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(defonce failures i64)
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(defn main [] ()
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(let [ns [5 3 9 1]
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fs [2.5 0.5 1.5]
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a (sorted (slice ns 0 4))
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b (sorted (slice fs 0 3))]
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(println (at (slice a) 0)) ; 1
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(println (at (slice a) 3)) ; 9
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(println (at (slice b) 0)) ; 0.5
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(println (length (slice b))) ; 3
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(free a)
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(free b))
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(let [ns [4 2 8]
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ar (arena-new 4096)
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c (sorted-in (slice ns 0 3) ar)]
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(println (at (slice c) 0)) ; 2
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(free-all ar))
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(let [ns [7 7 3]
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ws ["a" "b" "a"]]
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(println (distinct-count (slice ns 0 3))) ; 2
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(println (distinct-count (slice ws 0 3)))) ; 2
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(println (middle-of 6)) ; 6
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(println (middle-of 1.5)) ; 1.5
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(println (widen 3 0.0)) ; 3
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;; The guard, the condition and the restart are the concrete form's, emitted
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;; into the copy unchanged. 32 bytes is four i32 and the sixteen this fills
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;; are not.
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(set tight (heap-allocator))
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(set-alloc-budget tight 32)
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(handler-bind
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[(StorageExhausted [c]
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(set failures (+ failures 1))
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(set-alloc-budget tight (* 4 (alloc-budget tight)))
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(invoke-restart 'retry))]
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(let [ns [9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4]
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d (sorted-in (slice ns 0 16) tight)]
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(println (length (slice d))) ; 16
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(println (at (slice d) 0)) ; 0
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(free d)))
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(println (> failures 0)) ; true
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(set-alloc-budget tight 0))
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