Move code to new function `inters_lines`

Because we are going to complicate the criterium of association
between two eddies.

Overlap/CMakeLists.txt

@@ -7,7 +7,7 @@ if(MPI_Fortran_HAVE_F08_MODULE)
   add_executable(eddy_graph eddy_graph.f90 get_snapshot.f90 overlap.f90
     dispatch_snapshot.f90 recv_snapshot.f90 candidate_overlap.f90
     spher_polygon_area.f90 send_snapshot.f90 unit_edge_m.f90 config_graph.F90
-    read_grid.F90 read_snapshot.f90 read_eddy.f90)
+    read_grid.F90 read_snapshot.f90 read_eddy.f90 inters_lines.f90)
   target_link_libraries(eddy_graph PRIVATE EZMPI::ezmpi Jumble::jumble
     Shapelib_03::shapelib_03 Contour_531::contour_531 gpc_f Geometry::geometry
     MPI::MPI_Fortran Numer_Rec_95::numer_rec_95)
@@ -21,7 +21,7 @@ endif()
 add_subdirectory(Tests)
 target_sources(test_overlap PRIVATE overlap.f90 spher_polygon_area.f90
   candidate_overlap.f90 unit_edge_m.f90 config_graph.F90 read_grid.F90
-  read_snapshot.f90 read_eddy.f90)
+  read_snapshot.f90 read_eddy.f90 inters_lines.f90)
 target_sources(test_spher_polygon_area PRIVATE spher_polygon_area.f90)
 target_sources(test_read_snapshot PRIVATE read_snapshot.f90 read_eddy.f90
   read_grid.F90 config_graph.F90)

Overlap/inters_lines.f90

+module inters_lines_m
+
+  implicit none
+
+contains
+
+  logical function inters_lines(polyline_1, polyline_2, min_inters)
+
+    ! Do the two polylines intersect with a sufficient area of
+    ! intersection?
+
+    ! Libraries:
+    use contour_531, only: polyline
+    use gpc_f, only: gpc_polygon_clip_f, GPC_INT, polygon
+
+    use spher_polygon_area_m, only: spher_polygon_area
+    use spher_polyline_area_m, only: spher_polyline_area
+
+    type(polyline), intent(in):: polyline_1, polyline_2
+    real, intent(in):: min_inters ! minimum intersection between contours
+
+    ! Local:
+    type(polygon) res_pol
+
+    !-------------------------------------------------------------------------
+
+    call gpc_polygon_clip_f(GPC_INT, polygon(nparts = 1, &
+         part = [polyline_1], hole = [.false.]), polygon(nparts = 1, &
+         part = [polyline_2], hole = [.false.]), res_pol)
+
+    if (res_pol%nparts == 0) then
+       ! polyline_1 and polyline_2 do not overlap
+       inters_lines = .false.
+    else
+       ! polyline_1 and polyline_2 overlap
+       inters_lines = spher_polygon_area(res_pol) >= min_inters &
+            * min(abs(spher_polyline_area(polyline_1)), &
+            abs(spher_polyline_area(polyline_2)))
+    end if
+
+  end function inters_lines
+
+end module inters_lines_m

Overlap/overlap.f90

@@ -13,15 +13,13 @@ contains
 
     ! Libraries:
     use contour_531, only: polyline
-    use gpc_f, only: gpc_polygon_clip_f, GPC_INT, polygon
     use jumble, only: twopi
 
+    use inters_lines_m, only: inters_lines
     use candidate_overlap_m, only: candidate_overlap
     use config_graph_m, only: dist_lim, min_inters_speed
     use derived_types, only: snapshot
     use read_grid_m, only: nlon, nlat, periodic
-    use spher_polygon_area_m, only: spher_polygon_area
-    use spher_polyline_area_m, only: spher_polyline_area
     use unit_edge_m, only: unit_edge
 
     type(snapshot), intent(inout):: flow(:) ! (max_delta + 1)
@@ -41,7 +39,6 @@ contains
     integer i2 ! eddy index of successor
     integer l, n_select
     type(polyline) polyline_1, polyline_2
-    type(polygon) res_pol
 
     integer, allocatable:: selection(:)
     ! identifying numbers of a selection of extrema
@@ -99,20 +96,11 @@ contains
                    + floor((e1%extr%coord(1) - e2%extr%coord(1)) / twopi &
                    + 0.5) * twopi
 
-              call gpc_polygon_clip_f(GPC_INT, polygon(nparts = 1, &
-                   part = [polyline_1], hole = [.false.]), polygon(nparts = 1, &
-                   part = [polyline_2], hole = [.false.]), res_pol)
-
-              if (res_pol%nparts /= 0) then
-                 ! polyline_1 and polyline_2 overlap
-                 if (spher_polygon_area(res_pol) >= min_inters_speed &
-                      * min(abs(spher_polyline_area(polyline_1)), &
-                      abs(spher_polyline_area(polyline_2)))) then
-                    write(unit_edge, fmt = *) &
-                         (k - delta) * e_overestim + i1, k * e_overestim + i2
-                    e1%delta_out = min(e1%delta_out, delta)
-                    e2%delta_in = min(e2%delta_in, delta)
-                 end if
+              if (inters_lines(polyline_1, polyline_2, min_inters_speed)) then
+                 write(unit_edge, fmt = *) (k - delta) * e_overestim + i1, &
+                      k * e_overestim + i2
+                 e1%delta_out = min(e1%delta_out, delta)
+                 e2%delta_in = min(e2%delta_in, delta)
               end if
             end associate
          end DO