subroutine funcs(x,a,y,dyda,na,mmax,ndat,maxnd,mfit,lista)
c
c Subroutine to provide the Levenberg-Marquardt routines with
c the necessary information. It uses common blocks to get its information
c from the main program without putting it through the L-M routines.
c
      include 'constnts.inc'
      include 'data.inc'
      include 'model.inc'
c
      integer*4 na,ndat,mfit,first,mmax,maxnd
      real*8 x(ndat),y(maxnd),a(na),dyda(maxnd,mmax)
      real*8 ylo,yhi
      integer*4 lista(mfit)
c
      real*8 modvish(mxrec,mxfilt),modvisl(mxrec,mxfilt)
      real*8 modphas(mxrec,mxfilt)
      real*8 seprad,parad
      real*8 deltaa(mxparm)
      logical decstep
      data first/0/
c
      if(first.eq.0)then
       write(outc,'(a,a)')'Derivatives are calculated ',
     & 'initially using the following increments:'
       deltaa(1)=0.01D0                 ! Diameters [mas]
       deltaa(2)=deltaa(1)
       do 70 l=3,6
   70  deltaa(l)=0.01D0                 ! Diameter ratios
       deltaa(7)=0.001D0                ! Mag. differences
       deltaa(8)=deltaa(7)              
       deltaa(9)=deltaa(8)              
       deltaa(10)=0.001D0               ! a_true [mas]
       deltaa(11)=0.0001D0              ! e_true
       deltaa(12)=period/10000.D0       ! period [days]      
       deltaa(13)=period/10000.D0       ! epoch [days]
       deltaa(14)=0.01D0                ! inclination [degrees]
       deltaa(15)=0.01D0                ! asc_node [degrees]
       deltaa(16)=0.01D0                ! arg_peri [degrees]
       write(outc,'(a,a)')'diams ,-rat.,m-diffs.,a_true,',
     & 'e_true,period,epoch,inclin.,asc_node,arg_peri'
       write(outc,71)deltaa(1),(deltaa(j),j=6,7),(deltaa(j),j=10,16)
   71  format(1x,f5.3,2x,f5.3,2x,f5.3,4x,f5.3,2x,
     &  f6.4,2x,f5.3,1x,f5.3,2x,f5.3,3x,f5.3,3x,f5.3)
       write(outc,*)
       first=1
      endif
c
      diam(1,1)=a(1)
      diam(2,1)=a(2)
      dratio(1,2)=a(3)
      dratio(1,3)=a(4)
      dratio(2,2)=a(5)
      dratio(2,3)=a(6)
      delmag(2,1)=a(7)
      delmag(2,2)=a(8)
      delmag(2,3)=a(9)
      a_true=a(10)
      e_true=a(11)
      period=a(12)
      epoch=a(13)
      inclin=a(14)
      asc_node=a(15)
      arg_peri=a(16)

      call cadjmod
      mode=0
      call binavis(ndata,nfilt,mxrec,mxfilt,date,baseline,hours,
     &             lambda0,dlambda0,modvish,modphas,udata,vdata,
     &             seprad,parad,mode,ftcurve)
      do i=1,ndat
       id=i-((i-1)/ndata)*ndata
       ig=(i-1)/ndata+1
       y(i)=modvish(id,ig)
      enddo

c Now calculate derivatives (numerically)

      do j=1,mfit
       k=lista(j)
       decstep=.false.
       goto (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16)k
    1  diam(1,1)=a(1)-deltaa(1)
       goto 100
    2  diam(2,1)=a(2)-deltaa(2)
       goto 100
    3  dratio(1,2)=a(3)-deltaa(3)
       goto 100
    4  dratio(1,3)=a(4)-deltaa(4)
       goto 100
    5  dratio(2,2)=a(5)-deltaa(5)
       goto 100
    6  dratio(2,3)=a(6)-deltaa(6)
       goto 100
    7  delmag(2,1)=a(7)-deltaa(7)
       goto 100
    8  delmag(2,2)=a(8)-deltaa(8)
       goto 100
    9  delmag(2,3)=a(9)-deltaa(9)
       goto 100
   10  a_true=a(10)-deltaa(10)
       goto 100
   11  e_true=a(11)-deltaa(11)
       goto 100
   12  period=a(12)-deltaa(12)
       goto 100
   13  epoch=a(13)-deltaa(13)
       goto 100
   14  inclin=a(14)-deltaa(14)
       goto 100
   15  asc_node=a(15)-deltaa(15)
       goto 100
   16  arg_peri=a(16)-deltaa(16)
       goto 100
  100  call cadjmod
       call binavis(ndata,nfilt,mxrec,mxfilt,date,baseline,hours,
     &              lambda0,dlambda0,modvisl,modphas,udata,vdata,
     &              seprad,parad,mode,ftcurve)
       goto (21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36)k
   21  diam(1,1)=a(1)+deltaa(1)
       goto 110
   22  diam(2,1)=a(2)+deltaa(2)
       goto 110
   23  dratio(1,2)=a(3)+deltaa(3)
       goto 110
   24  dratio(1,3)=a(4)+deltaa(4)
       goto 110
   25  dratio(2,2)=a(5)+deltaa(5)
       goto 110
   26  dratio(2,3)=a(6)+deltaa(6)
       goto 110
   27  delmag(2,1)=a(7)+deltaa(7)
       goto 110
   28  delmag(2,2)=a(8)+deltaa(8)
       goto 110
   29  delmag(2,3)=a(9)+deltaa(9)
       goto 110
   30  a_true=a(10)+deltaa(10)
       goto 110
   31  e_true=a(11)+deltaa(11)
       goto 110
   32  period=a(12)+deltaa(12)
       goto 110
   33  epoch=a(13)+deltaa(13)
       goto 110
   34  inclin=a(14)+deltaa(14)
       goto 110
   35  asc_node=a(15)+deltaa(15)
       goto 110
   36  arg_peri=a(16)+deltaa(16)
       goto 110
  110  call cadjmod
       call binavis(ndata,nfilt,mxrec,mxfilt,date,baseline,hours,
     &              lambda0,dlambda0,modvish,modphas,udata,vdata,
     &              seprad,parad,mode,ftcurve)
       goto 41
   41  diam(1,1)=a(1)
       diam(2,1)=a(2)
       dratio(1,2)=a(3)
       dratio(1,3)=a(4)
       dratio(2,2)=a(5)
       dratio(2,3)=a(6)
       delmag(2,1)=a(7)
       delmag(2,2)=a(8)
       delmag(2,3)=a(9)
       a_true=a(10)
       e_true=a(11)
       period=a(12)
       epoch=a(13)
       inclin=a(14)
       asc_node=a(15)
       arg_peri=a(16)
       goto 120
  120  call cadjmod
       do i=1,ndat
        id=i-((i-1)/ndata)*ndata
        ig=(i-1)/ndata+1
        yhi=modvish(id,ig)
        ylo=modvisl(id,ig)
        dyda(i,k)=(yhi-ylo)/(2.D0*deltaa(k))
        if(abs(yhi-ylo).gt.0.001D0)decstep=.true.
       enddo
       if(decstep)deltaa(k)=deltaa(k)/2.d0
      enddo
      goto 200

  200 return
      end