src/gray_core.f90: cleanup

- add some comments
- annotate loops
- indent comments
- remove trailing whitespace
- reduce usage of opaque global variables
- use Fortran 90 logical operators
- use Fortran 2003 array syntax

src/beamdata.f90

@@ -12,7 +12,7 @@ contains
     use gray_params, only : raytracing_parameters
     use const_and_precisions, only : half,two
     implicit none
-    type(raytracing_parameters), intent(in) :: rtrparam
+    type(raytracing_parameters), intent(inout) :: rtrparam
     real(wp_),  dimension(:,:), intent(out), pointer :: ywork,ypwork, &
        gri,psjki,ppabs,ccci
     real(wp_), dimension(:,:,:), intent(out), pointer :: xc,du1,ggri
@@ -41,6 +41,7 @@ contains
     end if
     nray   = (nrayr-1)*nrayth + 1
     jkray1 = (jray1-2)*nrayth + 2
+    rtrparam%nray = nray
 
     if(nrayr>1) then
       twodr2 = two*(rwmax/(nrayr-1))**2

src/gray_params.f90

@@ -51,7 +51,7 @@ module gray_params
   type raytracing_parameters
     real(wp_) :: dst                ! Integration step size
     real(wp_) :: rwmax              ! Normalized maximum radius of beam power
-    integer :: nrayr, nrayth        ! Radial/angular number of rays
+    integer :: nray, nrayr, nrayth  ! Total/radial/angular number of rays
     integer :: igrad                ! Complex eikonal switch
     integer :: nstep                ! Max number of integration steps
     integer :: idst                 ! Choice of the integration variable

src/main.f90

@@ -408,8 +408,7 @@ contains
     use const_and_precisions, only : zero, degree
     use coreprofiles,         only : set_prfan, set_prfspl, temp, fzeff
     use dispersion,           only : expinit
-    use gray_params,          only : gray_parameters, print_parameters, &
-                                     headw, headl
+    use gray_params,          only : gray_parameters, print_parameters
     use beams,                only : launchangles2n, xgygcoeff
     use magsurf_data,         only : flux_average, dealloc_surfvec
     use beamdata,             only : init_btr, dealloc_beam
@@ -421,12 +420,12 @@ contains
     implicit none
 
     ! subroutine arguments
-    type(gray_parameters),   intent(in) :: params
+    type(gray_parameters),   intent(inout) :: params
     real(wp_),               intent(in)    :: pabs, icd
     real(wp_), dimension(:), intent(in)    :: jphi, jcd, dpdv, currins, pins
     real(wp_), intent(out) :: jphip, dpdvp, rhotj, rhotjava,       &
                               rhotp, rhotpav, drhotjava, drhotpav, &
-                              ratjamx,ratjbmx
+                              ratjamx, ratjbmx
 
     ! local variables
     real(wp_) :: ak0, bres, xgcn