# Update the transitive reduction
if te.tos.has(f) then return # Skip the reduction if there is a loop
- for x in te.dfroms.to_a do
+ # Remove transitive edges.
+ # Because the sets of direct is iterated, the list of edges to remove
+ # is stored and is applied after the iteration.
+ # The usual case is that no direct edges need to be removed,
+ # so start with a `null` list of edges.
+ var to_remove: nullable Array[E] = null
+ for x in te.dfroms do
var xe = self.elements[x]
if xe.tos.has(f) then
- te.dfroms.remove(x)
+ if to_remove == null then to_remove = new Array[E]
+ to_remove.add x
xe.dtos.remove(t)
end
end
- for x in fe.dtos.to_a do
+ if to_remove != null then
+ for x in to_remove do te.dfroms.remove(x)
+ to_remove.clear
+ end
+
+ for x in fe.dtos do
var xe = self.elements[x]
if xe.froms.has(t) then
xe.dfroms.remove(f)
- fe.dtos.remove(x)
+ if to_remove == null then to_remove = new Array[E]
+ to_remove.add x
end
end
+ if to_remove != null then
+ for x in to_remove do fe.dtos.remove(x)
+ end
+
fe.dtos.add t
te.dfroms.add f
end