Fix zero(InfiniteCardinal) (#42)

* Fix zero(InfiniteCardinal)

* Update cardinality.jl

* add test

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Co-authored-by: Lilith Hafner <[email protected]>

Author: LilithHafner

src/cardinality.jl

@@ -28,6 +28,7 @@ sign(::InfiniteCardinal) = 1
 angle(::InfiniteCardinal) = 0
 abs(a::InfiniteCardinal) = a
 zero(::InfiniteCardinal) = 0
+zero(::Type{<:InfiniteCardinal}) = 0
 one(::Type{<:InfiniteCardinal}) = 1
 oneunit(::Type{<:InfiniteCardinal}) = 1
 oneunit(::InfiniteCardinal) = 1

test/test_cardinality.jl

@@ -8,7 +8,7 @@ using Infinities, Base64, Base.Checked, Test
         @test angle(ℵ₀) ≡ 0
         @test Integer(∞) ≡ convert(Integer,∞) ≡ Integer(ℵ₀) ≡ convert(Integer, ℵ₀) ≡ ℵ₀
         @test abs(ℵ₀) ≡ ℵ₀
-        @test zero(ℵ₀) ≡ 0
+        @test zero(ℵ₀) ≡ zero(InfiniteCardinal{0}) ≡ 0
         @test one(ℵ₀) ≡ one(InfiniteCardinal{0}) ≡ oneunit(ℵ₀) ≡ oneunit(InfiniteCardinal{0}) ≡ 1
         @test isinf(ℵ₀) && !isfinite(ℵ₀)
         @test Integer(RealInfinity()) ≡ Integer(ComplexInfinity()) ≡ ℵ₀