Joseph Ferano
dad725afe4
swap!, reverse!, sort!, sort-by!, index-of, min-of, max-of, map!, reduce and filter, each written once over $t. Every call site in the corpus moves with them. min-of and max-of are not min and max because min and max are builtins over two or more numbers and nothing shadows a builtin. These reduce a slice, which is a different operation at a different arity. sort-bytes! did not collapse into sort!, and the reason is the point of the predicates: a [u8] is not ordered? and cannot be, because < is an instruction and comparing two slices lexicographically is a loop. It is sort-by! with bytes<? written in, one line, keeping its name and its stability note. sum-i32/sum-f32 and append-i64!/append-f64! stay for the reasons the spike gave. Not what the notes predicted: none of the ten collapses on a signature change alone. filter and reduce need copyable? because the checker demands it - reduce's accumulator at (Vec i32) is a double move - and the rest declare it because a slice of owning elements would have them duplicating headers.
106 lines
3.6 KiB
Plaintext
106 lines
3.6 KiB
Plaintext
;;;; Generics by monomorphisation, end to end.
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;;;;
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;;;; A [$t] binds a type variable in a defn signature and every call site
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;;;; instantiates the body at the types it passes. The body is checked once
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;;;; *abstractly*, with nothing substituted, so an operator the variable is
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;;;; not declared to support is refused at the definition and not at whichever
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;;;; call site happened to reach a type that worked — see generic-reject.flan
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;;;; and generic-runaway.flan for that half.
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;;;;
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;;;; What this program is asserting, in order: one variable at several types,
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;;;; a variable bound inside a slice, a generic calling a generic at its own
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;;;; variable so that instantiation has to be transitive, the four where
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;;;; predicates, two variables at once, println deferred to the instantiation,
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;;;; and the collapsed prelude family the whole feature was for.
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;; One variable, several types, and (ident 3) and (ident 7) share one copy.
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;; The identity needs its parameter once, so it needs nothing declared: a type
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;; variable is move-only by default and one move is what this is.
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(defn ident [x $t] $t x)
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;; The variable is bound *inside* a type constructor, which is a structural
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;; walk rather than a name match.
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(defn first-or [s [$t] d $t] $t
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{:where (copyable? $t)}
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(if (= (len s) 0) d (at s 0)))
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;; A generic calling a generic at its own variable: the copy of [swap!] is
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;; generated when [rotate!] is instantiated and not before.
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(defn rotate! [s [$t]] ()
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{:where (copyable? $t)}
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(dotimes [i (- (len s) 1)]
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(swap! s i (+ i 1))))
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;; numeric? admits + - * / %.
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(defn twice [x $t] $t
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{:where (numeric? $t)}
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(+ x x))
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;; equal? admits = and !=; ordered? admits < <= > >= min max, and entails
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;; equal? and copyable?.
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(defn count-of [s [$t] x $t] i32
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{:where (equal? $t)}
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(let [n 0]
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(dotimes [i (len s)]
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(when (= (at s i) x)
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(set n (+ n 1))))
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n))
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(defn clamp-to [x $t lo $t hi $t] $t
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{:where (ordered? $t)}
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(min (max x lo) hi))
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;; Two variables, and the second is determined by its own argument.
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(defn fst [a $t b $u] $t
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{:where [(copyable? $t) (copyable? $u)]}
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(do b a))
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;; println over a type variable is the one form the abstract pass defers to
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;; the instantiation, because its legality is only decidable after
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;; substituting. The structural printer is selected per copy.
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(defn show [x $t] ()
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{:where (copyable? $t)}
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(println x))
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(defn main [] ()
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(println (ident 3))
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(println (ident 4.5))
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(println (ident true))
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(println (ident 7))
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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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(println (first-or (slice ns 0 4) -1))
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(println (first-or (slice ns 0 0) -1))
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(rotate! (slice ns 0 4))
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(println (at ns 3))
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(println (twice 21))
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(println (twice 1.5))
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(println (count-of (slice ns 0 4) 9))
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(println (clamp-to 12 0 10))
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(println (clamp-to 0.5 1.0 9.0))
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(println (fst 8 true))
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(show 3)
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(show 4.5)
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(show "text")
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;; The collapsed prelude family, at both element types.
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(sort! (slice ns 0 4))
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(println (at ns 0))
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(sort-by! (slice fs 0 3) (fn [a b] (> a b)))
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(println (at fs 0))
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(reverse! (slice ns 0 4))
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(println (at ns 0))
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(map! (slice ns 0 4) (fn [x] (* x 2)))
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(println (reduce (slice ns 0 4) 0 (fn [a b] (+ a b))))
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(match (min-of (slice ns 0 4)) (Some m) (println m) _ (println -1))
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(match (max-of (slice fs 0 3)) (Some m) (println m) _ (println -1.0))
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(match (index-of (slice ns 0 4) 18) (Some i) (println i) _ (println -1))
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(let [a (arena-new 4096)
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keep (filter (slice ns 0 4) (fn [x] (> x 5)))]
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(println (len (as-slice keep)))
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(free keep)
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(free-all a))))
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