size for infinite bandwidth plusoperator (#148)

Author: jishnub

src/Operators/general/algebra.jl

@@ -16,7 +16,9 @@ struct PlusOperator{T,BI} <: Operator{T}
     end
 end
 
-Base.size(P::PlusOperator,k::Integer) = size(first(P.ops),k)
+_size(::PlusOperator{<:Any, NTuple{2,InfiniteCardinal{0}}}, k) = InfiniteCardinal{0}()
+_size(P, k) = size(first(P.ops),k)
+Base.size(P::PlusOperator,k::Integer) = _size(P, k)
 
 bandwidthsmax(ops) = mapreduce(bandwidths, (t1,t2) -> max.(t1, t2), ops, init = (-720, -720) #= approximate (-∞,-∞) =#)
 

test/SpacesTest.jl

@@ -76,6 +76,15 @@ using ApproxFunOrthogonalPolynomials
                 @test union(s, s, s, s) == s
             end
         end
+
+        M = Multiplication(Fun(PointSpace(1:3), [1:3;]), PointSpace(1:3))
+        @test (@inferred size(M)) == (3,3)
+        M2 = M + M
+        @test size(M2) == (3,3)
+        M = Multiplication(Fun(PointSpace(1:3), [1:3;]))
+        M2 = M + M
+        infty = ApproxFunBase.InfiniteCardinal{0}()
+        @test (@inferred size(M2)) == (infty, infty)
     end
 
     @testset "Derivative operator for HeavisideSpace" begin