Add LEMON graph structures and tests

src/Graphs.jl

@@ -557,6 +557,8 @@ include("vertexcover/random_vertex_cover.jl")
 include("Experimental/Experimental.jl")
 include("Parallel/Parallel.jl")
 include("Test/Test.jl")
+include("LEMON/LEMON.jl")
 
 using .LinAlg
+using .LEMON
 end # module

src/LEMON/LEMON.jl

@@ -0,0 +1,45 @@
+module LEMON
+
+using Graphs
+
+export LEMONGraph, LEMONDiGraph
+
+abstract type AbstractLEMONGraph <: AbstractGraph{Int} end
+
+struct LEMONGraph <: AbstractLEMONGraph
+    n::Int
+    m::Int
+
+    function LEMONGraph(n::Integer=0)
+        n >= 0 || throw(DomainError(n, "Number of vertices must be non-negative"))
+        return new(n, 0)
+    end
+end
+
+struct LEMONDiGraph <: AbstractLEMONGraph
+    n::Int
+    m::Int
+
+    function LEMONDiGraph(n::Integer=0)
+        n >= 0 || throw(DomainError(n, "Number of vertices must be non-negative"))
+        return new(n, 0)
+    end
+end
+
+Graphs.is_directed(::Type{LEMONGraph}) = false
+Graphs.is_directed(::Type{LEMONDiGraph}) = true
+
+Graphs.nv(g::AbstractLEMONGraph) = g.n
+Graphs.ne(g::AbstractLEMONGraph) = g.m
+
+Graphs.vertices(g::AbstractLEMONGraph) = 1:nv(g)
+
+function Base.show(io::IO, g::LEMONGraph)
+    return print(io, "{$(nv(g)), $(ne(g))} undirected LEMON graph")
+end
+
+function Base.show(io::IO, g::LEMONDiGraph)
+    return print(io, "{$(nv(g)), $(ne(g))} directed LEMON graph")
+end
+
+end

test/LEMON/lemon.jl

@@ -0,0 +1,39 @@
+using Graphs.LEMON
+
+@testset "LEMON" begin
+    @testset "Graph Construction" begin
+        g = LEMONGraph()
+        @test nv(g) == 0
+        @test ne(g) == 0
+        @test !is_directed(g)
+
+        g2 = LEMONGraph(5)
+        @test nv(g2) == 5
+        @test ne(g2) == 0
+
+        @test_throws DomainError LEMONGraph(-1)
+    end
+
+    @testset "DiGraph Construction" begin
+        g = LEMONDiGraph()
+        @test nv(g) == 0
+        @test ne(g) == 0
+        @test is_directed(g)
+
+        g2 = LEMONDiGraph(5)
+        @test nv(g2) == 5
+        @test ne(g2) == 0
+
+        @test_throws DomainError LEMONDiGraph(-1)
+    end
+
+    @testset "Basic Properties" begin
+        g = LEMONGraph(10)
+        @test vertices(g) == 1:10
+        @test eltype(g) == Int
+
+        dg = LEMONDiGraph(10)
+        @test vertices(dg) == 1:10
+        @test eltype(dg) == Int
+    end
+end

test/runtests.jl

@@ -148,6 +148,7 @@ tests = [
     "vertexcover/random_vertex_cover",
     "trees/prufer",
     "experimental/experimental",
+    "LEMON/lemon",
 ]
 
 @testset verbose = true "Graphs" begin