iterator order 0 (#78)

* allow rooted tree iterators with order zero

* set version to v2.10.4

Author: ranocha

Project.toml

@@ -1,7 +1,7 @@
 name = "RootedTrees"
 uuid = "47965b36-3f3e-11e9-0dcf-4570dfd42a8c"
 authors = ["Hendrik Ranocha <mail@ranocha.de> and contributors"]
-version = "2.10.3"
+version = "2.10.4"
 
 [deps]
 Latexify = "23fbe1c1-3f47-55db-b15f-69d7ec21a316"

src/RootedTrees.jl

@@ -500,7 +500,7 @@ Base.eltype(::Type{RootedTreeIterator{T}}) where T = RootedTree{T,Vector{T}}
 
 @inline function Base.iterate(iter::RootedTreeIterator{T}) where {T}
   iter.t.level_sequence[:] = one(T):iter.order
-  (iter.t, false)
+  (iter.t, iter.order <= 0)
 end
 
 @inline function Base.iterate(iter::RootedTreeIterator{T}, state) where {T}
@@ -537,7 +537,7 @@ end
 Counts all rooted trees of `order`.
 """
 function count_trees(order)
-  order < 1 && throw(ArgumentError("The `order` must be at least one."))
+  order < 0 && throw(ArgumentError("The `order` must be at least zero."))
 
   num = 0
   for _ in RootedTreeIterator(order)

test/runtests.jl

@@ -289,13 +289,13 @@ Plots.unicodeplots()
 
   # see butcher2008numerical, Table 302(I)
   @testset "number of trees" begin
-    number_of_rooted_trees = [1, 1, 2, 4, 9, 20, 48, 115, 286, 719]
-    for order in 1:10
+    number_of_rooted_trees = [1, 1, 1, 2, 4, 9, 20, 48, 115, 286, 719]
+    for order in 0:10
       num = 0
       for t in RootedTreeIterator(order)
         num += 1
       end
-      @test num == number_of_rooted_trees[order] == count_trees(order)
+      @test num == number_of_rooted_trees[order + 1] == count_trees(order)
     end
   end
 
@@ -785,15 +785,15 @@ end # @testset "RootedTree"
 
   # see butcher2008numerical, Table 302(I)
   @testset "number of trees" begin
-    number_of_rooted_trees = [1, 1, 2, 4, 9, 20, 48, 115, 286, 719]
-    for order in 1:10
+    number_of_rooted_trees = [1, 1, 1, 2, 4, 9, 20, 48, 115, 286, 719]
+    for order in 0:10
       num = 0
       for t in BicoloredRootedTreeIterator(order)
         num += 1
       end
       # number of plain rooted trees times number of possible color sequences
       # <= since not all possible color sequences are in canonical representation
-      @test num <= number_of_rooted_trees[order] * 2^order
+      @test num <= number_of_rooted_trees[order + 1] * 2^order
     end
   end