/*  written by Gosei Furuya <go.maxima@gmail.com> 
#  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.                
*/

/* to find integral factor for a diff form, if possible */
trans_toexact(_w):= block([anorm_table,a,b,c],
    if d(_w)@ _w # 0 then return("no answer")
    else (
	   anorm_table:norm_table,
	   a:makelist(concat('u,i),i,1,dim),
	   norm_table:map("*",a,norm_table),
	   for i:1 thru dim do
             ( extsubb2[i]:cons(basis[i]=norm_table[i]/basis[i],extsub[i])),
           b:_w & _w,
           c:( d(_w) & _w) /b,
           norm_table:anorm_table,
	   for i:1 thru dim do
             ( extsubb2[i]:cons(basis[i]=norm_table[i]/basis[i],extsub[i]))
           ),
	c
	);