Joseph Ferano
f35af50f51
Four corrections to the prose and one to the test, none to the design. The provenance line said "the name is Rust's or_else, the behaviour is Rust's unwrap_or", which conflates two functions that differ in both eagerness and return type — Rust's or_else takes a closure and answers another Option. Java's Optional.orElse is the exact match, and its lazy sibling orElseGet is the one already declined a paragraph above. The helper reaching or-else's None branch at an owning type asserted a refusal nobody had run. Compiled, it is "nothing here says what None is an Option of — annotate the function's return type or the binding", so the comment quotes that and the helper is a return type and nothing else: its other branch was never called, in a program whose header says every line is a claim. read-file's comment claimed both restarts arrive unchanged and the test runs use-value. Narrowed to the mechanism (nothing here establishes a handler) plus the half that is actually executed. And edn-read.flan now says what becomes of its defn wrapper when the computed-initialiser work lands, since that is the only thing keeping the motivating line from being written as the defvar.
195 lines
7.4 KiB
Plaintext
195 lines
7.4 KiB
Plaintext
;;;; Generics by monomorphisation, end to end.
|
|
;;;;
|
|
;;;; A [$t] binds a type variable in a defn signature and every call site
|
|
;;;; instantiates the body at the types it passes. The body is checked once
|
|
;;;; *abstractly*, with nothing substituted, so an operator the variable is
|
|
;;;; not declared to support is refused at the definition and not at whichever
|
|
;;;; call site happened to reach a type that worked — see generic-reject.flan
|
|
;;;; and generic-runaway.flan for that half.
|
|
;;;;
|
|
;;;; What this program is asserting, in order: one variable at several types,
|
|
;;;; a variable bound inside a slice, a generic calling a generic at its own
|
|
;;;; variable so that instantiation has to be transitive, the four where
|
|
;;;; predicates, two variables at once, println deferred to the instantiation,
|
|
;;;; the collapsed prelude family the whole feature was for, and the family
|
|
;;;; over (Option $t) — or-else and some? — which is the one that declares no
|
|
;;;; predicate at all, so a $t that owns storage instantiates it too.
|
|
|
|
;; One variable, several types, and (ident 3) and (ident 7) share one copy.
|
|
;; The identity needs its parameter once, so it needs nothing declared: a type
|
|
;; variable is move-only by default and one move is what this is.
|
|
(defn ident [x $t] $t x)
|
|
|
|
;; The variable is bound *inside* a type constructor, which is a structural
|
|
;; walk rather than a name match.
|
|
(defn first-or [s [$t] d $t] $t
|
|
(if (= (len s) 0) d (at s 0)))
|
|
|
|
;; A generic calling a generic at its own variable: the copy of [swap!] is
|
|
;; generated when [rotate!] is instantiated and not before.
|
|
(defn rotate! [s [$t]] ()
|
|
(dotimes [i (- (len s) 1)]
|
|
(swap! s i (+ i 1))))
|
|
|
|
;; numeric? admits + - * / %.
|
|
(defn twice [x $t] $t
|
|
{:where (numeric? $t)}
|
|
(+ x x))
|
|
|
|
;; equal? admits = and !=; ordered? admits < <= > >= min max, and entails
|
|
;; equal?.
|
|
(defn count-of [s [$t] x $t] i32
|
|
{:where (equal? $t)}
|
|
(let [n 0]
|
|
(dotimes [i (len s)]
|
|
(when (= (at s i) x)
|
|
(set n (+ n 1))))
|
|
n))
|
|
|
|
(defn clamp-to [x $t lo $t hi $t] $t
|
|
{:where (ordered? $t)}
|
|
(min (max x lo) hi))
|
|
|
|
;; Two variables, and the second is determined by its own argument.
|
|
(defn fst [a $t b $u] $t
|
|
(do b a))
|
|
|
|
;; println over a type variable is the one form the abstract pass defers to
|
|
;; the instantiation, because its legality is only decidable after
|
|
;; substituting. The structural printer is selected per copy.
|
|
(defn show [x $t] ()
|
|
(println x))
|
|
|
|
;; A cast to a type variable. [(t x)] is not a name [is_cast] knows — [t] is
|
|
;; not a machine type — so it is its own arm, and [numeric?] is what admits
|
|
;; it, because a cast produces a number. Inside the copy the target is
|
|
;; concrete and the emitter sees an ordinary cast.
|
|
(defn widen [x i32 d $t] $t
|
|
{:where (numeric? $t)}
|
|
(do d (t x)))
|
|
|
|
;; The builtins that take a *type name* as an argument, over a variable. Each
|
|
;; reaches the one list of what names a type; (map-new t i32) is the other.
|
|
(defn one-of [x $t] (Vec $t)
|
|
(let [v (vec-new t)]
|
|
(push v x)
|
|
v))
|
|
|
|
;; An empty (Option (Vec u8)), which main needs to reach or-else's None branch
|
|
;; at a type that owns storage. It is a function and not a bare None at the
|
|
;; call site because a bare None there is refused — "nothing here says what
|
|
;; None is an Option of" — and a return type is one of the two places the
|
|
;; checker names as somewhere to say it. It is also the shape every real caller
|
|
;; is in: what arrives at or-else came out of something, the way edn/read's
|
|
;; answer does.
|
|
(defn none-vec [] (Option (Vec u8))
|
|
None)
|
|
|
|
;; (zeroed) takes its type from the position it is written in, so a variable
|
|
;; in that position is answered by the instantiation like any other type.
|
|
(defn zero-of [x $t] $t
|
|
(do x (zeroed)))
|
|
|
|
;; The map operations over a key that is a type variable. The hash and the
|
|
;; equality are concrete symbols chosen from the concrete key type, so there
|
|
;; is nothing to emit here — these are deferred to the instantiation, the way
|
|
;; println is, and {:where (hashable? $t)} is what allows it: the refusal for
|
|
;; a key type that cannot be hashed lands at the call site, against a
|
|
;; requirement written down in this signature. Without the clause the type
|
|
;; (Map $t i32) is refused where it is written; see generic-map-reject.flan
|
|
;; for the call-site half.
|
|
(defn bump [k $t n i32] i32
|
|
{:where (hashable? $t)}
|
|
(let [m (map-new t i32)]
|
|
(reserve m 8)
|
|
(put m k n)
|
|
(put m k (+ n (match (get m k) (Some v) v _ 0)))
|
|
(let [c (clone m)
|
|
answer (+ (match (get c k) (Some v) v _ -1)
|
|
(if (has-key? c k) 1 0))]
|
|
(free c)
|
|
(free m)
|
|
answer)))
|
|
|
|
(defn main [] ()
|
|
(println (ident 3))
|
|
(println (ident 4.5))
|
|
(println (ident true))
|
|
(println (ident 7))
|
|
|
|
(let [ns [5 3 9 1]
|
|
fs [2.5 0.5 1.5]]
|
|
(println (first-or (slice ns 0 4) -1))
|
|
(println (first-or (slice ns 0 0) -1))
|
|
(rotate! (slice ns 0 4))
|
|
(println (at ns 3))
|
|
|
|
(println (twice 21))
|
|
(println (twice 1.5))
|
|
(println (count-of (slice ns 0 4) 9))
|
|
(println (clamp-to 12 0 10))
|
|
(println (clamp-to 0.5 1.0 9.0))
|
|
(println (fst 8 true))
|
|
|
|
(show 3)
|
|
(show 4.5)
|
|
(show "text")
|
|
|
|
;; The collapsed prelude family, at both element types.
|
|
(sort! (slice ns 0 4))
|
|
(println (at ns 0))
|
|
(sort-by! (slice fs 0 3) (fn [a b] (> a b)))
|
|
(println (at fs 0))
|
|
(reverse! (slice ns 0 4))
|
|
(println (at ns 0))
|
|
(map! (slice ns 0 4) (fn [x] (* x 2)))
|
|
(println (reduce (slice ns 0 4) 0 (fn [a b] (+ a b))))
|
|
(match (min-of (slice ns 0 4)) (Some m) (println m) _ (println -1))
|
|
(match (max-of (slice fs 0 3)) (Some m) (println m) _ (println -1.0))
|
|
(match (index-of (slice ns 0 4) 18) (Some i) (println i) _ (println -1))
|
|
|
|
;; or-else and some?, which are the same family over (Option $t) and take
|
|
;; no predicate: they move the payload out or read the tag, and neither is
|
|
;; an operation the variable has to be declared to support.
|
|
;;
|
|
;; Both branches at two scalar types, because a default that is returned
|
|
;; and a default that is discarded are two different lowerings and only one
|
|
;; of them is exercised by a call that happens to be Some.
|
|
(println (or-else (index-of (slice ns 0 4) 18) -1)) ; the Some branch
|
|
(println (or-else (index-of (slice ns 0 4) 77) -1)) ; the None branch
|
|
(println (or-else (max-of (slice fs 0 3)) 0.0))
|
|
(println (or-else (max-of (slice fs 0 0)) 0.0))
|
|
(println (some? (index-of (slice ns 0 4) 18)))
|
|
(println (some? (index-of (slice ns 0 4) 77)))
|
|
(println (some? (parse-i64 (bytes "12"))))
|
|
|
|
;; And at a $t that owns storage, which is the case the scalars above say
|
|
;; nothing about. What comes back is a *header* onto one of the two
|
|
;; buffers, so both are still the caller's to free — hence two frees and
|
|
;; not one, and the lengths are what say which header each answer holds.
|
|
(let [full (vec-new u8)
|
|
empty (vec-new u8)]
|
|
(push full 65)
|
|
(push full 66)
|
|
(println (len (or-else (Some full) empty))) ; 2, full's header
|
|
(println (len (or-else (none-vec) empty))) ; 0, empty's
|
|
(free full)
|
|
(free empty))
|
|
|
|
(println (widen 3 0.0))
|
|
(println (widen 3 (i64 0)))
|
|
(println (zero-of 9))
|
|
|
|
;; One written body, two key types, two emitted copies.
|
|
(println (bump 7 10))
|
|
(println (bump "key" 3))
|
|
|
|
(let [a (arena-new 4096)
|
|
keep (filter (slice ns 0 4) (fn [x] (> x 5)))
|
|
one (one-of 4.5)]
|
|
(println (len (as-slice keep)))
|
|
(println (at (as-slice one) 0))
|
|
(free one)
|
|
(free keep)
|
|
(free-all a))))
|