Fixups

[hcoop/zz_old/domtool.git] / src / mlton_util.sml

(*
Domtool (http://hcoop.sf.net/)
Copyright (C) 2004-2005  Adam Chlipala

This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
*)

(* Utility functions *)

structure MltonUtil :> MLTON_UTIL =
struct
    fun merge (L1 : ('a * int) list, L2 : ('a * int) list) acc =
	case (L1, L2) of
	    (_, []) => List.revAppend (acc, L1)
	  | ([], _) => List.revAppend (acc, L2)
	  | (n1::t1, n2::t2) =>
	    if #2 n1 > #2 n2 then
		merge (t1, L2) (n1 :: acc)
	    else
		merge (L1, t2) (n2 :: acc)

    fun split n L acc =
	if n <= 0 then
	    (acc, L)
	else
	    case L of
		[] => (acc, [])
	      | h::t => split (n-1) t (h::acc)

    fun mergeSort L =
	case L of
	    [] => L
	  | [a] => L
	  | _ =>
	    let
		val mid = length L div 2
		val (L1, L2) = split mid L []
	    in
		merge (mergeSort L1, mergeSort L2) []
	    end
end