anchor.diff:  c
     310 continue
   c     # zero-order extrapolation:
  -      do 315 m=1,meqn
  -         do 315 jbc=1,mbc
  -            do 315 i = 1-mbc,mx+mbc
  +      do m=1,meqn
  +         do jbc=1,mbc
  +            do i = 1-mbc,mx+mbc
                  q(i,1-jbc,m) = q(i,1,m)
  -  315       continue
  +            end do
  +         end do
  +      end do
         go to 399
   
     320 continue
   c     # periodic:
  -      do 325 m=1,meqn
  -         do 325 jbc=1,mbc
  -            do 325 i = 1-mbc, mx+mbc
  -               q(i,1-jbc,m) = q(i,my+1-jbc,m)
  -  325       continue
  +      write(6,*) 'clawpack4.6_bc2_default : ', 
  +     &            'Periodic BCs should not be set in bc2'
  +      stop
         go to 399
   
     330 continue
   c     # solid wall (assumes 3'rd component is velocity or momentum in y):
  -      do 335 m=1,meqn
  -         do 335 jbc=1,mbc
  -            do 335 i = 1-mbc,mx+mbc
  +      do m=1,meqn
  +         do jbc=1,mbc
  +            do i = 1-mbc,mx+mbc
                  q(i,1-jbc,m) = q(i,jbc,m)
  -  335       continue
  -c     # negate the normal velocity:
  -      do 336 jbc=1,mbc
  -         do 336 i = 1-mbc, mx+mbc
  +            end do
  +         end do
  +      end do
  +c     # negate the normal velocity:
  +      do jbc=1,mbc
  +         do i = 1-mbc, mx+mbc
               q(i,1-jbc,3) = -q(i,jbc,3)
  -  336    continue
  +         end do
  +      end do
         go to 399
   
     399 continue
  
positive.code: c
    110 continue
  c     # zero-order extrapolation:
        do 115 m=1,meqn
           do 115 ibc=1,mbc
              do 115 j = 1-mbc,my+mbc
                 q(1-ibc,j,m) = q(1,j,m)
    115       continue
        go to 199
  
    120 continue
  c     # periodic:
        do 125 m=1,meqn
           do 125 ibc=1,mbc
              do 125 j = 1-mbc, my+mbc
                 q(1-ibc,j,m) = q(mx+1-ibc,j,m)
    125       continue
        go to 199
  
    130 continue
  c     # solid wall (assumes 2'nd component is velocity or momentum in x):
        do 135 m=1,meqn
           do 135 ibc=1,mbc
              do 135 j = 1-mbc, my+mbc
                 q(1-ibc,j,m) = q(ibc,j,m)
    135       continue
  c     # negate the normal velocity:
        do 136 ibc=1,mbc
           do 136 j = 1-mbc, my+mbc
              q(1-ibc,j,2) = -q(ibc,j,2)
    136    continue
        go to 199
  
    199 continue
  
negative.code: 
    210 continue
  c     # zero-order extrapolation:
        do m=1,meqn
           do ibc=1,mbc
              do j = 1-mbc,my+mbc
                 q(mx+ibc,j,m) = q(mx,j,m)
              end do
           end do
        end do
        go to 299
  
    220 continue
  c     # periodic:
        write(6,*) 'clawpack4.6_bc2_default : ', 
       &            'Periodic BCs should not be set in bc2'
        stop
        go to 299
  
    230 continue
  c     # solid wall (assumes 2'nd component is velocity or momentum in x):
        do m=1,meqn
           do ibc=1,mbc
              do j = 1-mbc, my+mbc
                 q(mx+ibc,j,m) = q(mx+1-ibc,j,m)
              end do
           end do
        end do
  c     # negate the normal velocity:
        do ibc=1,mbc
           do j = 1-mbc, my+mbc
              q(mx+ibc,j,2) = -q(mx+1-ibc,j,2)
           end do
        end do
        go to 299
  
    299 continue
  