close #869

JuliaControl · Sep 8, 2023 · ce4f79f · ce4f79f
1 parent 4f6bdba
commit ce4f79f
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diff --git a/lib/ControlSystemsBase/src/types/SisoTfTypes/conversion.jl b/lib/ControlSystemsBase/src/types/SisoTfTypes/conversion.jl
@@ -1,6 +1,6 @@
 function Base.convert(::Type{SisoZpk{T,TR}}, f::SisoRational{T2}) where {T<:Number, TR<:Number, T2<:Number}
     if length(f.num) == 0
-        return SisoZpk(T[],TR[],0)
+        return SisoZpk(T[],TR[],zero(T))
     elseif all(f.den == zero(f.den))
         error("Zero denominator, this should not be possible") # NOTE: Should we keep this?
     end

diff --git a/lib/ControlSystemsBase/test/test_conversion.jl b/lib/ControlSystemsBase/test/test_conversion.jl
@@ -188,4 +188,12 @@ myss = ss(mytf)
 test = ss([-1 2 3; 0 -2 3; 0 0 -3],[1;2;3],[1 2 3], [0])
 @test tf(test) isa TransferFunction
 
+
+# Issue https://github.com/JuliaControl/ControlSystems.jl/issues/869
+
+sys = tf(ssrand(2,2,2))
+sys.matrix[1,1] = 0
+syszpk = zpk(sys)
+@test syszpk isa TransferFunction{Continuous, ControlSystemsBase.SisoZpk{Float64, ComplexF64}}
+
 end