From ee4467856c50c7e493ee5fcc562f194f207ccd8c Mon Sep 17 00:00:00 2001
From: fchrstou <filippos.christou@ikr.uni-stuttgart.de>
Date: Thu, 26 Jan 2023 17:06:12 +0100
Subject: [PATCH] Add empty constructors

---
 src/di_multigraph_adjlist.jl  | 3 +++
 src/multigraph_adjlist.jl     | 3 +++
 test/di_multigraph_adjlist.jl | 9 ++++++++-
 test/multigraph_adjlist.jl    | 9 ++++++++-
 4 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/di_multigraph_adjlist.jl b/src/di_multigraph_adjlist.jl
index 6f587c0..8caa8a4 100644
--- a/src/di_multigraph_adjlist.jl
+++ b/src/di_multigraph_adjlist.jl
@@ -45,6 +45,9 @@ function DiMultigraph(adjmx::AbstractMatrix{U}) where {U<:Integer}
     end
     DiMultigraph{Int}(adjlist, m)
 end
+DiMultigraph() = DiMultigraph(0)
+DiMultigraph{T}() where T = DiMultigraph(0)
+DiMultigraph{T}(t::T) where T = DiMultigraph(t)
 function DiMultigraph(n::T) where {T<:Integer} 
     n >= 0 || error("Number of vertices should be non-negative")
     adjlist = Dict{T, Vector{T}}()
diff --git a/src/multigraph_adjlist.jl b/src/multigraph_adjlist.jl
index 2fe2944..7b2ae77 100644
--- a/src/multigraph_adjlist.jl
+++ b/src/multigraph_adjlist.jl
@@ -48,6 +48,9 @@ function Multigraph(adjmx::AbstractMatrix{U}) where {U<:Integer}
     end
     Multigraph{Int}(adjlist, m)
 end
+Multigraph() = Multigraph(0)
+Multigraph{T}() where T = Multigraph(0)
+Multigraph{T}(t::T) where T = Multigraph(t)
 function Multigraph(n::T) where {T<:Integer} 
     n >= 0 || error("Number of vertices should be non-negative")
     adjlist = Dict{T, Vector{T}}()
diff --git a/test/di_multigraph_adjlist.jl b/test/di_multigraph_adjlist.jl
index a158ff3..027402b 100644
--- a/test/di_multigraph_adjlist.jl
+++ b/test/di_multigraph_adjlist.jl
@@ -72,4 +72,11 @@ add_vertex!(g)
 @test indegree(g) != outdegree(g)
 
 dmg0 = DiMultigraph(0)
-@test nv(dmg0) == ne(dmg0) == 0
\ No newline at end of file
+@test nv(dmg0) == ne(dmg0) == 0
+
+#test constructor
+@test try DiMultigraph(1); true; catch; false; end
+@test try DiMultigraph{Int}(1); true; catch; false; end
+@test try DiMultigraph(); true; catch; false; end
+@test try DiMultigraph{Int}(); true; catch; false; end
+
diff --git a/test/multigraph_adjlist.jl b/test/multigraph_adjlist.jl
index 19fc409..2fe9462 100644
--- a/test/multigraph_adjlist.jl
+++ b/test/multigraph_adjlist.jl
@@ -68,4 +68,11 @@ add_vertex!(g)
 @test indegree(g) == outdegree(g)
 
 mg0 = Multigraph(0)
-@test nv(mg0) == ne(mg0) == 0
\ No newline at end of file
+@test nv(mg0) == ne(mg0) == 0
+
+#test constructor
+@test try Multigraph(1); true; catch; false; end
+@test try Multigraph{Int}(1); true; catch; false; end
+@test try Multigraph(); true; catch; false; end
+@test try Multigraph{Int}(); true; catch; false; end
+