Sort using a custom comparator: Difference between revisions

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{{output}}
{{output}}
<pre>{"party", "come", "good", "time", "aid", "all", "for", "men", "now", "the", "the", "the", "is", "of", "to", "to"}</pre>
<pre>{"party", "come", "good", "time", "aid", "all", "for", "men", "now", "the", "the", "the", "is", "of", "to", "to"}</pre>

=={{header|ATS}}==

<lang ATS>(* The following demonstrates a few ways to customize the
comparator. *)

#include "share/atspre_staload.hats"
staload UN = "prelude/SATS/unsafe.sats"

%{^
#include <strings.h>
%}

extern fn
strcasecmp : (string, string) -<> int = "mac#strcasecmp"

fn
sort_strings_1 (lst : List string,
cmp : (string, string) -<> int)
:<!wrt> List string =
list_vt2t (list_mergesort_fun<string> (lst, cmp))

fn
sort_strings_2 (lst : List string,
cmp : (string, string) -<cloref> int)
:<!wrt> List string =
list_vt2t (list_mergesort_cloref<string> (lst, cmp))

var one = 1
val p_one = addr@ one

fn
sort_using_a_template_function (lst : List string)
:<!wrt> List string =
(* There is no actual callback here. The comparison code is expanded
directly into the sort code. *)
let
implement
list_mergesort$cmp<string> (x, y) =
let
val m = length x
and n = length y
in
if m < n then
1
else if n < m then
~1
else
strcasecmp (x, y)
end
in
(* The list mergesort template functions in the ATS prelude return
_linear_ lists. Thus the call to list_vt2t to cast that result
to an ordinary list. *)
list_vt2t (list_mergesort<string> lst)
end

fn
sort_using_an_ordinary_function (lst : List string)
:<!wrt> List string =
(* Rather than expand the comparison code, incorporate a function
call into the sort implementation. *)
let
fn
cmp (x : string,
y : string)
:<> int =
let
val m = length x
and n = length y
in
if m < n then
1
else if n < m then
~1
else
strcasecmp (x, y)
end
in
list_vt2t (list_mergesort_fun<string> (lst, cmp))
end

fn
sort_the_way_it_works_for_qsort_in_C (lst : List string)
:<!wrt> List string =
(* Here we have a true callback to an ordinary function. *)
let
fn
cmp (x : string,
y : string)
:<> int =
let
val m = length x
and n = length y
in
if m < n then
1
else if n < m then
~1
else
strcasecmp (x, y)
end
in
sort_strings_1 (lst, cmp)
end

fn
sort_using_a_closure (lst : List string)
:<!wrt> List string =
(* Incorporate a closure into the sort implementation. (Standard C
does not have closures.) *)
let
fn
cmp (x : string,
y : string)
:<cloref> int =
let
(* Merely to demonstrate this is a closure instead of regular
function, get the value of "one" from a global variable. *)
val @(pf, fpf | p) = $UN.ptr_vtake{int} p_one
val one = !p
prval () = fpf pf

val m = length x
and n = length y
in
if m < n then
one
else if n < m then
~one
else
strcasecmp (x, y)
end
in
list_vt2t (list_mergesort_cloref<string> (lst, cmp))
end

fn
sort_by_calling_back_to_a_closure (lst : List string)
:<!wrt> List string =
(* Incorporate a closure into the sort implementation. (Standard C
does not have closures.) *)
let
fn
cmp (x : string,
y : string)
:<cloref> int =
let
(* Merely to demonstrate this is a closure instead of regular
function, get the value of "one" from a global variable. *)
val @(pf, fpf | p) = $UN.ptr_vtake{int} p_one
val one = !p
prval () = fpf pf

val m = length x
and n = length y
in
if m < n then
one
else if n < m then
~one
else
strcasecmp (x, y)
end
in
sort_strings_2 (lst, cmp)
end

implement
main0 () =
let
val unsorted =
$list{string}
("Here", "are", "some", "sample", "strings",
"to", "be", "sorted")

val sorted1 = sort_using_a_template_function unsorted
val sorted2 = sort_using_an_ordinary_function unsorted
val sorted3 = sort_the_way_it_works_for_qsort_in_C unsorted
val sorted4 = sort_using_a_closure unsorted
val sorted5 = sort_by_calling_back_to_a_closure unsorted
in
println! unsorted;
println! sorted1;
println! sorted2;
println! sorted3;
println! sorted4;
println! sorted5
end</lang>

{{out}}
<pre>$ patscc -DATS_MEMALLOC_GCBDW -O3 sort_using_custom_comparator.dats -lgc && ./a.out
Here, are, some, sample, strings, to, be, sorted
strings, sample, sorted, Here, some, are, be, to
strings, sample, sorted, Here, some, are, be, to
strings, sample, sorted, Here, some, are, be, to
strings, sample, sorted, Here, some, are, be, to
strings, sample, sorted, Here, some, are, be, to</pre>


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