RosettaCodeData/Task/Sort-numbers-lexicographically/ATS/sort-numbers-lexicographically.ats
2023-07-01 13:44:08 -04:00

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(* The Rosetta Code lexicographic sort task. *)
#include "share/atspre_staload.hats"
staload UN = "prelude/SATS/unsafe.sats"
#define NIL list_nil ()
#define :: list_cons
fn
uint_to_digit (n : uint)
: char =
int2char0 (g0u2i n + char2int0 '0')
fn
int_to_string {n : nat}
(n : int n)
: string =
if iseqz n then
"0"
else
let
fun
loop {i : nat | i <= 20}
.<i>.
(buf : &array (char, 21),
i : int i,
n : uint)
: [j : nat | j <= 20]
int j =
if (i = 0) + (iseqz n) then
i
else
let
val i1 = pred i
in
buf[i1] := uint_to_digit (n mod 10u);
loop (buf, i1, n / 10u)
end
var buf = @[char][21] ('\0')
val j = loop (buf, 20, g0i2u n)
val p = ptr_add<char> (addr@ buf, j)
in
strptr2string (string0_copy ($UN.cast{string} p))
end
fn
iota1 {n : pos}
(n : int n)
: list ([i : pos | i <= n] int i, n) =
let
typedef t = [i : pos | i <= n] int i
fun
loop {i : nat | i <= n}
.<i>.
(i : int i,
accum : list (t, n - i))
: list (t, n) =
if i = 0 then
accum
else
loop (pred i, i :: accum)
in
loop (n, NIL)
end
fn
reverse_map_numbers_to_strings
{n : int}
(nums : list ([i : nat] int i, n))
: list (string, n) =
let
typedef t = [i : nat] int i
fun
loop {i : nat | i <= n}
.<n - i>.
(nums : list (t, n - i),
accum : list (string, i))
: list (string, n) =
case+ nums of
| NIL => accum
| head :: tail =>
loop {i + 1} (tail, int_to_string head :: accum)
prval () = lemma_list_param nums
in
loop {0} (nums, NIL)
end
fn
reverse_map_strings_to_numbers
{n : int}
(strings : list (string, n))
: list (int, n) =
let
macdef string_to_int (s) =
$extfcall (int, "atoi", ,(s))
fun
loop {i : nat | i <= n}
.<n - i>.
(strings : list (string, n - i),
accum : list (int, i))
: list (int, n) =
case+ strings of
| NIL => accum
| head :: tail =>
loop {i + 1} (tail, string_to_int head :: accum)
prval () = lemma_list_param strings
in
loop {0} (strings, NIL)
end
fn
lexicographic_iota1
{n : pos}
(n : int n)
: list (int, n) =
let
val numstrings =
reverse_map_numbers_to_strings (iota1 n)
(* One could use a MSB-first radix sort here, but I will use what
is readily available. *)
implement
list_mergesort$cmp<string> (x, y) =
~compare (x, y)
in
reverse_map_strings_to_numbers
(list_vt2t (list_mergesort<string> numstrings))
end
implement
main0 () =
begin
println! (lexicographic_iota1 13);
println! (lexicographic_iota1 100)
end