Fix printing of slices of OrthogonalPolynomial (#180)

* Possible fix

* Be less specific

Author: DanielVandH

src/ClassicalOrthogonalPolynomials.jl

@@ -71,7 +71,7 @@ abstract type AbstractOPLayout <: AbstractBasisLayout end
 struct OPLayout <: AbstractOPLayout end
 MemoryLayout(::Type{<:OrthogonalPolynomial}) = OPLayout()
 
-
+Base.isassigned(P::OrthogonalPolynomial, x, n) = (x ∈ axes(P,1)) && (n ∈ axes(P,2))
 
 sublayout(::AbstractOPLayout, ::Type{<:Tuple{<:AbstractAffineQuasiVector,<:Slice}}) = MappedOPLayout()
 

test/runtests.jl

@@ -79,3 +79,8 @@ end
     @test_throws ErrorException jacobimatrix(MyIncompleteJacobi())
     @test_throws ErrorException plan_transform(MyIncompleteJacobi(), 5)
 end
+
+@testset "Issue #179" begin
+    @test startswith(sprint(show, MIME"text/plain"(), Chebyshev()[0.3, :]; context=(:compact=>true, :limit=>true)), "ℵ₀-element view(::ChebyshevT{Float64}, 0.3, :)")
+    @test startswith(sprint(show, MIME"text/plain"(), Jacobi(0.2, 0.5)[-0.7, :]; context=(:compact=>true, :limit=>true)), "ℵ₀-element view(::Jacobi{Float64}, -0.7, :)")
+end