automorphism_group fix for rank 0 matroids + added test

oscar-system · Sep 14, 2023 · 07c40b0 · 07c40b0
1 parent ebee98c
commit 07c40b0
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diff --git a/src/Combinatorics/Matroids/matroids.jl b/src/Combinatorics/Matroids/matroids.jl
@@ -864,4 +864,7 @@ julia> automorphism_group(M)
 Group([ (3,4), (1,2), (2,3) ])
 ```
 """
-automorphism_group(m::Matroid) = automorphism_group(IncidenceMatrix(bases(m));action=:on_cols)
+function automorphism_group(m::Matroid) 
+  length(m) > 0 || throw(ArgumentError("The matroid should not be empty.")) 
+  rank(m) < 1 ? automorphism_group(dual_matroid(m)) : automorphism_group(IncidenceMatrix(bases(m));action=:on_cols)
+end
diff --git a/test/Combinatorics/Matroids/Matroids.jl b/test/Combinatorics/Matroids/Matroids.jl
@@ -343,5 +343,6 @@
     @testset "matroid automorphism" begin
         M = uniform_matroid(3, 5)
         @test order(automorphism_group(M)) == 120
+        @test automorphism_group(uniform_matroid(0, 2)) == symmetric_group(2)
     end
 end