/* File:      flraggavg.P
**
** Author(s): Guizhen Yang 
**
** Contact:   flora-users@lists.sourceforge.net
**
** Copyright (C) The Research Foundation of SUNY, 1999-2001
**
** FLORA-2 is free software; you can redistribute it and/or modify it under the
** terms of the GNU Library General Public License as published by the Free
** Software Foundation; either version 2 of the License, or (at your option)
** any later version.
** 
** FLORA-2 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 Library General Public License for
** more details.
** 
** You should have received a copy of the GNU Library General Public License
** along with FLORA-2; if not, write to the Free Software Foundation,
** Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
** 
** $Id: flraggavg.P,v 1.8 2003/06/18 07:01:22 kifer Exp $
** 
*/


:- compiler_options([xpp_on]).

#include "flora_terms.flh"

:- import ground/1, member/2 from basics.

:- import flora_warning_line/1 from flrprint.



/*********************************************************************
  fllibavg(+Var,+VarList,+Goal,-Avg)
*********************************************************************/
fllibavg(Var,[],Goal,Avg) :-
	!,
	findall(Var,Goal,Matches),
	flora_avgaux(Matches,Avg).

fllibavg(Var,VarList,Goal,Avg) :-
	ground(VarList),
	!,
	findall(Var,Goal,Matches),
	flora_avgaux(Matches,Avg).

fllibavg(Var,VarList,Goal,Avg) :-
	!,
	findall(flora_result(Var,VarList),Goal,Matches),
	findall(Grp,member(flora_result(_,Grp),Matches),GL),
	sort(GL,Groups),
	member(VarList,Groups),
	findall(D,member(flora_result(D,VarList),Matches),DL),
	flora_avgaux(DL,Avg).


/********************************************************************
  flora_avgaux(+List,-Avg).
  flora_avgaux(+List,-CurrSum,-CurrNum,-Avg,-Warning)
********************************************************************/
flora_avgaux(Matches,Avg) :-
	flora_avgaux(Matches,_,_,Avg,Warning),
	( var(Warning) ->
	    true
	;
	  flora_warning_line("discarding non-numeric values while computing average")
	).


flora_avgaux([],Sum,Num,Avg,_) :-
	!,
	(var(Sum) -> fail; Avg is Sum/Num).

flora_avgaux([H|L],Sum,Num,Avg,Warning) :-
	!,
	( number(H) ->
	    ( var(Sum) ->
		S=H,
		N=1
	      ;
	        S is Sum+H,
		N is Num+1
	    ),
	    flora_avgaux(L,S,N,Avg,Warning)
	;
	  Warning=[],
	  flora_avgaux(L,Sum,Num,Avg,_)
	).