some updates and a new example

src/dag_module.f90

@@ -16,6 +16,9 @@ module dag_module
         character(len=:),allocatable :: label !! used for diagraph
         character(len=:),allocatable :: attributes !! used for diagraph
     end type edge
+    interface edge
+        procedure :: edge_constructor
+    end interface edge
 
     type :: vertex
         !! a vertex of a directed acyclic graph (DAG)
@@ -63,6 +66,23 @@ module dag_module
     contains
 !*******************************************************************************
 
+!*******************************************************************************
+!>
+!  Constructor for [[edge]] type.
+
+    pure elemental function edge_constructor(ivertex,label,attributes) result(e)
+
+    integer,intent(in),optional :: ivertex
+    character(len=*),intent(in),optional :: label
+    character(len=*),intent(in),optional :: attributes
+    type(edge) :: e
+    e%ivertex = ivertex
+    if (present(label)) e%label = label
+    if (present(attributes)) e%attributes = attributes
+
+    end function edge_constructor
+!*******************************************************************************
+
 !*******************************************************************************
 !>
 !  Destroy the `dag`.
@@ -120,31 +140,11 @@ subroutine add_edge(me,e,label,attributes)
 
     if (allocated(me%edges)) then
         if (.not. any(e==me%edges%ivertex)) then ! don't add if already there
-
-            ! me%edges = [me%edges, edge(e,label=label,attributes=attributes)]
-            if (present(label) .and. present(attributes)) then
-                me%edges = [me%edges, edge(e,label=label,attributes=attributes)]
-            else if (.not. present(label) .and. present(attributes)) then
-                me%edges = [me%edges, edge(e,attributes=attributes)]
-            else if (present(label) .and. .not. present(attributes)) then
-                me%edges = [me%edges, edge(e,label=label)]
-            else
-                me%edges = [me%edges, edge(e)]
-            end if
+            me%edges = [me%edges, edge(e,label=label,attributes=attributes)]
             call sort_ascending(me%edges)
         end if
     else
-        allocate(me%edges(1))
-        ! me%edges = [edge(e,label=label,attributes=attributes)]
-        if (present(label) .and. present(attributes)) then
-            me%edges = [edge(e,label=label,attributes=attributes)]
-        else if (.not. present(label) .and. present(attributes)) then
-            me%edges = [edge(e,attributes=attributes)]
-        else if (present(label) .and. .not. present(attributes)) then
-            me%edges = [edge(e,label=label)]
-        else
-            me%edges = [edge(e)]
-        end if
+        me%edges = [edge(e,label=label,attributes=attributes)]
     end if
 
     end subroutine add_edge
@@ -216,6 +216,8 @@ subroutine dag_set_vertices(me,nvertices,labels)
     character(len=*),dimension(nvertices),intent(in),optional :: labels !! vertex name strings
     integer :: i !! counter
 
+    if (nvertices<=0) error stop 'error: nvertices must be >= 1'
+
     if (allocated(me%vertices)) deallocate(me%vertices)
 
     me%n = nvertices
@@ -444,8 +446,10 @@ function dag_generate_digraph(me,rankdir,dpi) result(str)
 
     ! define the vertices:
     do i=1,me%n
-        has_label      = allocated(me%vertices(i)%label)
+        has_label = allocated(me%vertices(i)%label)
+        if (has_label) has_label = me%vertices(i)%label /= ''
         has_attributes = allocated(me%vertices(i)%attributes)
+        if (has_attributes) has_attributes = me%vertices(i)%attributes /= ''
         if (has_label) label = 'label="'//trim(adjustl(me%vertices(i)%label))//'"'
         if (has_label .and. has_attributes) then
             attributes = '['//trim(adjustl(me%vertices(i)%attributes))//','//label//']'
@@ -479,8 +483,10 @@ function dag_generate_digraph(me,rankdir,dpi) result(str)
             if (.not. compress) then
                 ! Example:   1 -> 2 [penwidth=2, arrowhead=none]
                 do j=1,n_edges
-                    has_label      = allocated(me%vertices(i)%edges(j)%label)
+                    has_label = allocated(me%vertices(i)%edges(j)%label)
+                    if (has_label) has_label = me%vertices(i)%edges(j)%label /= ''
                     has_attributes = allocated(me%vertices(i)%edges(j)%attributes)
+                    if (has_attributes) has_attributes = me%vertices(i)%edges(j)%attributes /= ''
                     if (has_label) label = 'label="'//trim(adjustl(me%vertices(i)%edges(j)%label))//'"'
                     if (has_label .and. has_attributes) then
                         attributes = '['//trim(adjustl(me%vertices(i)%edges(j)%attributes))//','//label//']'

test/dag_example_3.f90

@@ -0,0 +1,96 @@
+!*******************************************************************************
+!>
+!  DAG module test program: Advent of Code 2023 Day 25 (test problem).
+
+    program dag_example_3
+
+    use dag_module
+
+    implicit none
+
+    type(dag) :: d
+    integer :: i, n_nodes
+    character(len=3),dimension(:),allocatable :: labels
+
+    character(len=*),parameter :: filetype = 'pdf'  !! filetype for output plot ('pdf', png', etc.)
+
+    n_nodes = 0
+    !allocate(labels(0))
+    do i = 1, 2
+        ! first pass just gets the nodes, 2nd gets the dependencies
+        call process(i, 'jqt', ['rhn', 'xhk', 'nvd'])
+        call process(i, 'rsh', ['frs', 'pzl', 'lsr'])
+        call process(i, 'xhk', ['hfx'])
+        call process(i, 'cmg', ['qnr', 'nvd', 'lhk', 'bvb'])
+        call process(i, 'rhn', ['xhk', 'bvb', 'hfx'])
+        call process(i, 'bvb', ['xhk', 'hfx'])
+        call process(i, 'pzl', ['lsr', 'hfx', 'nvd'])
+        call process(i, 'qnr', ['nvd'])
+        call process(i, 'ntq', ['jqt', 'hfx', 'bvb', 'xhk'])
+        call process(i, 'nvd', ['lhk'])
+        call process(i, 'lsr', ['lhk'])
+        call process(i, 'rzs', ['qnr', 'cmg', 'lsr', 'rsh'])
+        call process(i, 'frs', ['qnr', 'lhk', 'lsr'])
+        call process(i, 'hfx')
+        call process(i, 'lhk')
+        if (i==1) then
+            write(*,*) 'set_vertices !'
+            call d%set_vertices(n_nodes, labels=labels)
+        end if
+    end do
+
+    call d%save_digraph('test3.dot','RL',300)
+    call execute_command_line('cat test3.dot')
+    call execute_command_line('dot -T'//filetype//' -o test3.'//filetype//' test3.dot')
+
+    contains
+        subroutine process(icase, node, dependson)
+            integer,intent(in) :: icase
+            character(len=3),intent(in) :: node
+            character(len=3),dimension(:),intent(in),optional :: dependson
+            character(len=100),dimension(:),allocatable :: edge_attributes
+            integer :: i !! counter
+            integer,dimension(1) :: idx
+            character(len=*),parameter :: DEFAULT_EDGE = 'arrowhead=none'
+            character(len=*),parameter :: EDGES_TO_CUT = 'arrowhead=none,color=red'
+
+            if (icase==1) then
+                n_nodes = n_nodes + 1
+                if (allocated(labels)) then
+                    labels = [labels, node]
+                else
+                    labels = [node]
+                end if
+            else
+                if (present(dependson)) then
+                    allocate(edge_attributes(size(dependson)))
+                    edge_attributes = DEFAULT_EDGE
+                    if (node=='pzl' .and. any(findloc(labels,'hfx')>0)) then
+                        idx = findloc(dependson,'hfx'); i = idx(1)
+                        edge_attributes(i) = EDGES_TO_CUT
+                        call d%set_edges(node_index(node), node_index(dependson), attributes = edge_attributes)
+                    else if (node=='cmg' .and. any(findloc(labels,'bvb')>0)) then
+                        idx = findloc(dependson,'bvb'); i = idx(1)
+                        edge_attributes(i) = EDGES_TO_CUT
+                        call d%set_edges(node_index(node), node_index(dependson), attributes = edge_attributes)
+                    else if (node=='jqt' .and. any(findloc(labels,'nvd')>0)) then
+                        idx = findloc(dependson,'nvd'); i = idx(1)
+                        edge_attributes(i) = EDGES_TO_CUT
+                        call d%set_edges(node_index(node), node_index(dependson), attributes = edge_attributes)
+                    else
+                        call d%set_edges(node_index(node), node_index(dependson))
+                    end if
+                end if
+            end if
+        end subroutine process
+
+        pure elemental integer function node_index(node)
+            !! find the node number for this name
+            character(len=3),intent(in) :: node
+            integer,dimension(1) :: idx
+            idx = findloc(labels,node)
+            node_index = idx(1)
+        end function node_index
+
+    end program dag_example_3
+!*******************************************************************************