+Style compliance in external/drifters code

  Revised the external/drifters code to bring it into closer alignment with the
MOM6 style guide at https://github.com/mom-ocean/MOM6/wiki/Code-style-guide.
This includes using standard syntax to document variable units, the addition of
'implicit none ; private', explicit public statements, and a licensing statement
to the files that were missing one, and modifications to follow the MOM6 2-point
indenting convention.  All answers are bitwise identical.

config_src/external/drifters/MOM_particles.F90

@@ -1,26 +1,28 @@
 !> A set of dummy interfaces for compiling the MOM6 drifters code
 module MOM_particles_mod
 
+! This file is part of MOM6. See LICENSE.md for the license.
+
 use MOM_grid,         only : ocean_grid_type
 use MOM_time_manager, only : time_type, get_date, operator(-)
 use MOM_variables,    only : thermo_var_ptrs
+use particles_types_mod, only : particles, particles_gridded
 
+implicit none ; private
 
-use particles_types_mod, only: particles, particles_gridded
-
-public particles_run, particles_init, particles_save_restart, particles_end
+public particles, particles_run, particles_init, particles_save_restart, particles_end
 
 contains
 
 !> Initializes particles container "parts"
 subroutine particles_init(parts, Grid, Time, dt, u, v)
   ! Arguments
- type(particles), pointer, intent(out) :: parts !< Container for all types and memory
- type(ocean_grid_type), target, intent(in) :: Grid !< Grid type from parent model
- type(time_type), intent(in) :: Time !< Time type from parent model
- real, intent(in)            :: dt !< particle timestep in seconds
- real, dimension(:,:,:),intent(in)      :: u !< Zonal velocity field
- real, dimension(:,:,:),intent(in)      :: v !< Meridional velocity field
+  type(particles), pointer, intent(out) :: parts !< Container for all types and memory
+  type(ocean_grid_type), target, intent(in) :: Grid !< Grid type from parent model
+  type(time_type), intent(in) :: Time !< Time type from parent model
+  real, intent(in)            :: dt   !< particle timestep [s]
+  real, dimension(:,:,:), intent(in)    :: u !< Zonal velocity field [m s-1]
+  real, dimension(:,:,:), intent(in)    :: v !< Meridional velocity field [m s-1]
 
 end subroutine particles_init
 
@@ -29,30 +31,30 @@ subroutine particles_run(parts, time, uo, vo, ho, tv, stagger)
   ! Arguments
   type(particles), pointer :: parts !< Container for all types and memory
   type(time_type), intent(in) :: time !< Model time
-  real, dimension(:,:,:),intent(in) :: uo !< Ocean zonal velocity (m/s)
-  real, dimension(:,:,:),intent(in) :: vo !< Ocean meridional velocity (m/s)
-  real, dimension(:,:,:),intent(in) :: ho !< Ocean layer thickness [H ~> m or kg m-2]
-  type(thermo_var_ptrs), intent(in) :: tv !< structure containing pointers to available thermodynamic fields
+  real, dimension(:,:,:), intent(in) :: uo !< Ocean zonal velocity [m s-1]
+  real, dimension(:,:,:), intent(in) :: vo !< Ocean meridional velocity [m s-1]
+  real, dimension(:,:,:), intent(in) :: ho !< Ocean layer thickness [H ~> m or kg m-2]
+  type(thermo_var_ptrs),  intent(in) :: tv !< structure containing pointers to available thermodynamic fields
   integer, optional, intent(in) :: stagger !< Flag for whether velocities are staggered
 
 end subroutine particles_run
 
 
 !>Save particle locations (and sometimes other vars) to restart file
-subroutine particles_save_restart(parts,temp,salt)
-! Arguments
-type(particles), pointer :: parts !< Container for all types and memory
-real,dimension(:,:,:),optional,intent(in) :: temp !< Optional container for temperature
-real,dimension(:,:,:),optional,intent(in) ::  salt !< Optional container for salinity
+subroutine particles_save_restart(parts, temp, salt)
+  ! Arguments
+  type(particles), pointer :: parts !< Container for all types and memory
+  real, dimension(:,:,:), optional, intent(in) :: temp !< Optional container for temperature
+  real, dimension(:,:,:), optional, intent(in) :: salt !< Optional container for salinity
 
 end subroutine particles_save_restart
 
 !> Deallocate all memory and disassociated pointer
-subroutine particles_end(parts,temp,salt)
-! Arguments
-type(particles), pointer :: parts !< Container for all types and memory
-real,dimension(:,:,:),optional,intent(in) :: temp !< Optional container for temperature
-real,dimension(:,:,:),optional,intent(in) :: salt !< Optional container for salinity
+subroutine particles_end(parts, temp, salt)
+  ! Arguments
+  type(particles), pointer :: parts !< Container for all types and memory
+  real, dimension(:,:,:), optional, intent(in) :: temp !< Optional container for temperature
+  real, dimension(:,:,:), optional, intent(in) :: salt !< Optional container for salinity
 
 end subroutine particles_end
 

config_src/external/drifters/MOM_particles_types.F90

@@ -1,12 +1,15 @@
 !> Dummy data structures and methods for drifters package
 module particles_types_mod
 
+! This file is part of MOM6. See LICENSE.md for the license.
+
 use MOM_grid, only : ocean_grid_type
-use mpp_domains_mod, only: domain2D
+use MOM_domains, only: domain2D
 
+implicit none ; private
 
 !> Container for gridded fields
-type :: particles_gridded
+type, public :: particles_gridded
   type(domain2D), pointer :: domain !< MPP parallel domain
   integer :: halo !< Nominal halo width
   integer :: isc !< Start i-index of computational domain
@@ -60,7 +63,7 @@ module particles_types_mod
 
 
 !>xyt is a data structure containing particle position and velocity fields.
-type :: xyt
+type, public :: xyt
   real :: lon !< Longitude of particle (degree N or unit of grid coordinate)
   real :: lat !< Latitude of particle (degree N or unit of grid coordinate)
   real :: day      !< Day of this record (days)
@@ -77,7 +80,7 @@ module particles_types_mod
 end type xyt
 
 !>particle types are data structures describing a tracked particle
-type :: particle
+type, public :: particle
   type(particle), pointer :: prev=>null() !< Previous link in list
   type(particle), pointer :: next=>null() !< Next link in list
 ! State variables (specific to the particles, needed for restarts)
@@ -109,19 +112,19 @@ module particles_types_mod
 
 
 !>A buffer structure for message passing
-type :: buffer
+type, public :: buffer
   integer :: size=0 !< Size of buffer
   real, dimension(:,:), pointer :: data !< Buffer memory
 end type buffer
 
 !> A wrapper for the particle linked list (since an array of pointers is not allowed)
-type :: linked_list
+type, public :: linked_list
   type(particle), pointer :: first=>null() !< Pointer to the beginning of a linked list of parts
 end type linked_list
 
 
 !> A grand data structure for the particles in the local MOM domain
-type :: particles !; private
+type, public :: particles !; private
   type(particles_gridded) :: grd !< Container with all gridded data
   type(linked_list), dimension(:,:), allocatable :: list !< Linked list of particles
   type(xyt), pointer :: trajectories=>null() !< A linked list for detached segments of trajectories