anchor.diff:  		type(options_type),intent(in)::options
   		integer,dimension(io_maxDims)::dims	!note, io_maxDims is included from io_routines.
   		logical :: use_boundary,use_interior
  -		
  +		! MODULE variables : ext_winds_ curstep, curfile, nfiles, steps_in_file, file_list
   		ext_winds_curstep=ext_winds_curstep+1
   		if (ext_winds_curstep>ext_winds_steps_in_file) then
   			ext_winds_curfile=ext_winds_curfile+1
  
positive.code: 		logical :: boundary_value
  		integer::nx,ny,nz,i
  		real::domainsize
  		
  		curfile=1
  		if (options%restart) then
  
negative.code: 		type(bc_type),intent(inout)::bc
  		type(options_type),intent(in)::options
  		integer,dimension(io_maxDims)::dims	!note, io_maxDims is included from io_routines.
  		! MODULE variables : ext_winds_ curstep, curfile, nfiles, steps_in_file, file_list
  		ext_winds_curfile=1
  		if (options%restart) then
  			ext_winds_curstep=options%restart_step
  		else
  			ext_winds_curstep=1
  		endif
  		ext_winds_nfiles=options%ext_winds_nfiles
  		allocate(ext_winds_file_list(ext_winds_nfiles))
  		ext_winds_file_list=options%ext_wind_files
  		call io_getdims(ext_winds_file_list(ext_winds_curfile),"U", dims)
  		if (dims(1)==3) then
  			ext_winds_steps_in_file=1
  		else
  			ext_winds_steps_in_file=dims(dims(1)+1) !dims(1) = ndims
  		endif
  		
  ! 		ext_winds_curstep=ext_winds_curstep+1
  		do while (ext_winds_curstep>ext_winds_steps_in_file)
  			ext_winds_curfile=ext_winds_curfile+1
  			if (ext_winds_curfile>ext_winds_nfiles) then
  				stop "Ran out of files to process!"
  			endif
  			ext_winds_curstep=ext_winds_curstep-ext_winds_steps_in_file 
  			!instead of setting=1, this way we can set an arbitrary starting point multiple files in
  			call io_getdims(ext_winds_file_list(ext_winds_curfile),"U", dims)
  			if (dims(1)==3) then
  				ext_winds_steps_in_file=1
  			else
  				ext_winds_steps_in_file=dims(dims(1)+1) !dims(1) = ndims; dims(ndims+1)=ntimesteps
  			endif
  		enddo
  		
  		call read_var(domain%u,    ext_winds_file_list(ext_winds_curfile),"U",      bc%ext_winds%geolut,ext_winds_curstep,.FALSE.)
  		call read_var(domain%v,    ext_winds_file_list(ext_winds_curfile),"V",      bc%ext_winds%geolut,ext_winds_curstep,.FALSE.)
  