flan/test/programs/text.flan
Joseph Ferano dad725afe4 The prelude's per-type families collapse: 22 functions become 10, 27 become 16
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.
2026-09-13 14:49:11 +07:00

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;;;; The prelude's byte predicates, parse-i64, and the two number helpers.
;;;;
;;;; The cases are chosen so a wrong implementation fails one: a prefix longer
;;;; than the string (which must answer false, not trap), the empty prefix and
;;;; the whole string as its own prefix, a prefix that matches at the wrong
;;;; end, and for parse-i64 every shape strtoll answers 0 for — "", "abc",
;;;; "12x", "-" — each of which a caller could not tell from a real 0.
(defn show-bool [b bool] ()
(print (if b "t" "f")))
(defn main [] i32
(show-bool (bytes=? (bytes "abc") (bytes "abc"))) ; t
(show-bool (bytes=? (bytes "abc") (bytes "abd"))) ; f same length
(show-bool (bytes=? (bytes "abc") (bytes "ab"))) ; f prefix, not equal
(show-bool (bytes=? (bytes "") (bytes ""))) ; t
(println "")
(show-bool (starts-with? (bytes "hello") (bytes "hel"))) ; t
(show-bool (starts-with? (bytes "hello") (bytes "llo"))) ; f matches the end
(show-bool (starts-with? (bytes "hi") (bytes "hiya"))) ; f longer, no trap
(show-bool (starts-with? (bytes "hello") (bytes ""))) ; t
(show-bool (starts-with? (bytes "hello") (bytes "hello"))) ; t
(println "")
(show-bool (ends-with? (bytes "hello") (bytes "llo"))) ; t
(show-bool (ends-with? (bytes "hello") (bytes "hel"))) ; f matches the start
(show-bool (ends-with? (bytes "hi") (bytes "hiya"))) ; f longer, no trap
(show-bool (ends-with? (bytes "hello") (bytes ""))) ; t
(show-bool (ends-with? (bytes "hello") (bytes "hello"))) ; t
(println "")
;; First occurrence, and None for a byte that is not there.
(print (match (index-of (bytes "banana") \a) (Some i) i None -1))
(print " ")
(print (match (index-of (bytes "banana") \z) (Some i) i None -1))
(print " ")
(print (match (index-of (bytes "") \a) (Some i) i None -1))
(println "")
;; Accepted.
(print (match (parse-i64 (bytes "0")) (Some v) v None -999)) (print " ")
(print (match (parse-i64 (bytes "42")) (Some v) v None -999)) (print " ")
(print (match (parse-i64 (bytes "-42")) (Some v) v None -999)) (print " ")
(print (match (parse-i64 (bytes "+7")) (Some v) v None -999)) (print " ")
(print (match (parse-i64 (bytes "9007199254740993")) (Some v) v None -999))
(println "")
;; Refused. Each of these is a 0 out of strtoll, which is the point.
(print (match (parse-i64 (bytes "")) (Some v) v None -999)) (print " ")
(print (match (parse-i64 (bytes "abc")) (Some v) v None -999)) (print " ")
(print (match (parse-i64 (bytes "12x")) (Some v) v None -999)) (print " ")
(print (match (parse-i64 (bytes "-")) (Some v) v None -999)) (print " ")
(print (match (parse-i64 (bytes " 1")) (Some v) v None -999))
(println "")
(print (sign-f32 3.5)) (print " ")
(print (sign-f32 -3.5)) (print " ")
(print (sign-f32 0.0))
(println "")
;; t = 1.0 must return b exactly, which a + t*(b - a) does not always do.
(print (lerp 0.0 10.0 0.0)) (print " ")
(print (lerp 0.0 10.0 0.25)) (print " ")
(print (lerp 0.0 10.0 1.0)) (print " ")
(print (lerp 2.0 -2.0 0.5))
(println "")
;; The RNG ranges, off a fixed seed, so the numbers are the sequence and not
;; just "something in range". An empty range answers lo and must not divide.
(rand-seed 7)
(dotimes [i 5]
(when (> i 0) (print " "))
(print (rand-i32-range 10 20)))
(println "")
(print (rand-i32-range 5 5)) (print " ")
(print (rand-i32-range 5 -5))
(println "")
(rand-seed 7)
(dotimes [i 3]
(when (> i 0) (print " "))
(print (rand-f32-range 0.0 1.0)))
(println "")
0)