flan/test/programs/slices.flan
Joseph Ferano 96ab4c9cf0 Retire the per-type printers, since print says all of it
print-str, print-i64, print-f64, print-bytes, print-line and newline leave
the prelude. print and println are the whole printing surface now, and print
is the better call at every one of the sites that used them: it is the same
structural walk without the newline, so the no-newline case the family was
kept for is covered, and it takes the value as it is. The old print-i64
forced an explicit (i64 x) at every call site, because this language widens
nothing implicitly; that cast is gone from 127 places.

Dropping it moves one answer. hash-grid returns u64, and the cast through
the signed printer showed sand-headless's hash as -2851001042534928384.
print routes a u64 through flan_u64_to_bytes, so it now prints
15595743031174623232 — the same 64 bits, read as the unsigned number they
are. The pinned expectation follows the correction.

test-flan-dev.el and test_session.ml both reached for print-line as "a name
the prelude has"; they reach for rand-seed instead.
2026-09-12 05:32:25 +07:00

83 lines
3.4 KiB
Plaintext

;;;; The prelude's in-place slice algorithms.
;;;;
;;;; Every input here is chosen so that a wrong implementation passes nothing.
;;;; The sort input is unsorted, has duplicates, has negatives and has an odd
;;;; length, so a comparison with the wrong sense, an off-by-one that drops the
;;;; last element, and a swap that loses an equal key all show up. The second
;;;; sort is reverse-sorted, which is the worst case for insertion sort and the
;;;; case a no-op comparison would pass. The third sorts a *subslice* and then
;;;; prints the whole owning array: a slice is ptr+len into its owner, so the
;;;; five elements inside the range must be sorted and the three outside it
;;;; must be untouched. That last one is the property that dies silently if a
;;;; slice parameter ever starts being copied.
(defvar xs [7 i32])
(defvar ys [5 i32])
(defvar zs [8 i32])
(defn show [s [i32]]
(dotimes [i (len s)]
(when (> i 0) (print " "))
(print (at s i)))
(println ""))
(defn load-xs []
(set (at xs 0) 5)
(set (at xs 1) -3)
(set (at xs 2) 5)
(set (at xs 3) 0)
(set (at xs 4) 12)
(set (at xs 5) -3)
(set (at xs 6) 7))
(defn main [] i32
(load-xs)
(show (slice xs 0 (len xs))) ; 5 -3 5 0 12 -3 7
;; Reading the whole slice, before anything reorders it.
(print (sum-i32 (slice xs 0 (len xs)))) (println "") ; 23
(print (match (min-i32 (slice xs 0 (len xs))) (Some v) v None 99))
(println "") ; -3
(print (match (max-i32 (slice xs 0 (len xs))) (Some v) v None 99))
(println "") ; 12
;; First index, not the last: 5 appears at 0 and at 2.
(print (match (index-of-i32 (slice xs 0 (len xs)) 5) (Some v) v None -1))
(println "") ; 0
(print (match (index-of-i32 (slice xs 0 (len xs)) 4) (Some v) v None -1))
(println "") ; -1
;; An empty slice has no least element, and None is the answer.
(print (match (min-i32 (slice xs 3 3)) (Some v) v None 99))
(println "") ; 99
;; Reverse of an odd-length slice: the middle element stays put.
(reverse-i32! (slice xs 0 (len xs)))
(show (slice xs 0 (len xs))) ; 7 -3 12 0 5 -3 5
;; And of a two-element one, the smallest case that can actually move.
(reverse-i32! (slice xs 0 2))
(show (slice xs 0 (len xs))) ; -3 7 12 0 5 -3 5
(load-xs)
(sort-i32! (slice xs 0 (len xs)))
(show (slice xs 0 (len xs))) ; -3 -3 0 5 5 7 12
;; Reverse-sorted: the case a comparison that never fires would pass.
(set (at ys 0) 5) (set (at ys 1) 4) (set (at ys 2) 3)
(set (at ys 3) 2) (set (at ys 4) 1)
(sort-i32! (slice ys 0 (len ys)))
(show (slice ys 0 (len ys))) ; 1 2 3 4 5
;; A subslice, with the elements on both sides left alone.
(set (at zs 0) 100) (set (at zs 1) 9) (set (at zs 2) -1)
(set (at zs 3) 9) (set (at zs 4) 4) (set (at zs 5) 0)
(set (at zs 6) 200) (set (at zs 7) 300)
(sort-i32! (slice zs 1 6))
(show (slice zs 0 (len zs))) ; 100 -1 0 4 9 9 200 300
;; Degenerate lengths must do nothing rather than run off an end.
(sort-i32! (slice zs 0 0))
(reverse-i32! (slice zs 0 0))
(sort-i32! (slice zs 2 3))
(reverse-i32! (slice zs 2 3))
(show (slice zs 0 (len zs))) ; 100 -1 0 4 9 9 200 300
0)