anchor.diff:  
       DOUBLE PRECISION  hvR, hvL, vR, vL
       double precision z
  +
  +    integer icom, jcom
  +    double precision dtcom, dxcom, dycom, tcom
  +    common /comxyt/ dtcom,dxcom,dycom,tcom,icom,jcom
   
       if (ixy .eq. 1) then
           mu=2
  
positive.code: !!            ENDIF
              !! if s == 0, returns 1
              z = sign(1.d0,s(i,mw))
              amdq(i,1:3) = amdq(i,1:3) + (1-z)/2*fwave(i,1:3,mw)
              apdq(i,1:3) = apdq(i,1:3) + (z+1)/2*fwave(i,1:3,mw)
          ENDDO
      ENDDO
  
  
negative.code:     DOUBLE PRECISION     qr(1-mbc:maxm+mbc,meqn)
      DOUBLE PRECISION   apdq(1-mbc:maxm+mbc,meqn)
      DOUBLE PRECISION   amdq(1-mbc:maxm+mbc,meqn)
      DOUBLE PRECISION   auxl(1-mbc:maxm+mbc,*)
      DOUBLE PRECISION   auxr(1-mbc:maxm+mbc,*)
  
      DOUBLE PRECISION :: grav, dry_tolerance, sea_level
      COMMON /common_swe/ grav, dry_tolerance, sea_level
  