Type asesrtions in BandedMatrix conversion (#159)

* return type assertions in BandedMatrix

* concrete printshow

* assertions with variables

Author: jishnub

src/Operators/general/algebra.jl

@@ -346,6 +346,8 @@ function getindex(P::TimesOperator,k::AbstractVector)
     vec(Matrix(P[1:1,k]))
 end
 
+_rettype(::Type{BandedMatrix{T}}) where {T} = BandedMatrix{T,Matrix{T},Base.OneTo{Int}}
+_rettype(T) = T
 for TYP in (:Matrix, :BandedMatrix, :RaggedMatrix)
     @eval function $TYP(V::SubOperator{T,TO,Tuple{UnitRange{Int},UnitRange{Int}}}) where {T,TO<:TimesOperator}
         P = parent(V)
@@ -406,12 +408,14 @@ for TYP in (:Matrix, :BandedMatrix, :RaggedMatrix)
 
         # The following returns a banded Matrix with all rows
         # for large k its upper triangular
-        BA = convert($TYP{T}, P.ops[end][krl[end,1]:krl[end,2],jr])
+        RT = $TYP{T}
+        RT2 = _rettype(RT)
+        BA::RT2 = convert(RT, P.ops[end][krl[end,1]:krl[end,2],jr])::RT
         for m = (length(P.ops)-1):-1:1
-            BA = convert($TYP{T}, P.ops[m][krl[m,1]:krl[m,2],krl[m+1,1]:krl[m+1,2]])*BA
+            BA = convert(RT, P.ops[m][krl[m,1]:krl[m,2],krl[m+1,1]:krl[m+1,2]])::RT * BA
         end
 
-        $TYP{T}(BA)
+        RT(BA)::RT2
     end
 end
 

src/show.jl

@@ -34,9 +34,9 @@ summarystr(B::Operator) = string(typeof(B).name.name, " : ", domainspace(B), " 
 summary(io::IO, B::Operator) = print(io, summarystr(B))
 
 struct PrintShow
-    str
+    c::Char
 end
-Base.show(io::IO,N::PrintShow) = print(io,N.str)
+Base.show(io::IO, N::PrintShow) = print(io, N.c)
 
 show(io::IO, B::Operator; kw...) = summary(io, B)
 
@@ -49,57 +49,57 @@ function show(io::IO, ::MIME"text/plain", B::Operator;header::Bool=true)
         if isbanded(B) && isinf(size(B,1)) && isinf(size(B,2))
             BM=B[1:10,1:10]
 
-            M=Matrix{Any}(undef,11,11)
-            fill!(M,PrintShow("⋅"))
+            M=Matrix{Union{eltype(B), PrintShow}}(undef,11,11)
+            fill!(M,PrintShow('⋅'))
             for j = 1:size(BM,2),k = colrange(BM,j)
                 M[k,j]=BM[k,j]
             end
 
             for k=max(1,11-bandwidth(B,2)):11
-                M[k,end]=PrintShow("⋱")
+                M[k,end]=PrintShow('⋱')
             end
             for j=max(1,11-bandwidth(B,1)):10
-                M[end,j]=PrintShow("⋱")
+                M[end,j]=PrintShow('⋱')
             end
 
             print_array(io, M)
         elseif isinf(size(B,1)) && isinf(size(B,2))
             BM=B[1:10,1:10]
 
-            M=Matrix{Any}(undef,11,11)
+            M=Matrix{Union{eltype(B), PrintShow}}(undef,11,11)
             for k=1:10,j=1:10
                 M[k,j]=BM[k,j]
             end
 
-            M[1,end]=PrintShow("⋯")
-            M[end,1]=PrintShow("⋮")
+            M[1,end]=PrintShow('⋯')
+            M[end,1]=PrintShow('⋮')
 
             for k=2:11
-                M[k,end]=M[end,k]=PrintShow("⋱")
+                M[k,end]=M[end,k]=PrintShow('⋱')
             end
 
             print_array(io, M)
         elseif isinf(size(B,1))
             BM=B[1:10,1:size(B,2)]
 
-            M=Matrix{Any}(undef,11,size(B,2))
+            M=Matrix{Union{eltype(B), PrintShow}}(undef,11,size(B,2))
             for k=1:10,j=1:size(B,2)
                 M[k,j]=BM[k,j]
             end
             for k=1:size(B,2)
-                M[end,k]=PrintShow("⋮")
+                M[end,k]=PrintShow('⋮')
             end
 
             print_array(io, M)
         elseif isinf(size(B,2))
             BM=B[1:size(B,1),1:10]
 
-            M=Matrix{Any}(undef,size(B,1),11)
+            M=Matrix{Union{eltype(B), PrintShow}}(undef,size(B,1),11)
             for k=1:size(B,1),j=1:10
                 M[k,j]=BM[k,j]
             end
             for k=1:size(B,1)
-                M[k,end]=PrintShow("⋯")
+                M[k,end]=PrintShow('⋯')
             end
 
             print_array(io, M)