Storage-type promotion

Author: arnavk23

src/cat.jl

@@ -46,8 +46,15 @@ function hcat(A::AbstractLinearOperator, B::AbstractLinearOperator)
     hcat_ctprod!(res, adjoint(A), adjoint(B), Ancol, Ancol + Bncol, w, α, β)
   args5 = (has_args5(A) && has_args5(B))
   S = promote_type(storage_type(A), storage_type(B))
-  isconcretetype(S) ||
-    throw(LinearOperatorException("storage types cannot be promoted to a concrete type"))
+  if !isconcretetype(S)
+    if isconcretetype(storage_type(A))
+      S = storage_type(A)
+    elseif isconcretetype(storage_type(B))
+      S = storage_type(B)
+    else
+      S = Vector{T}
+    end
+  end
   CompositeLinearOperator(T, nrow, ncol, false, false, prod!, tprod!, ctprod!, args5, S = S)
 end
 
@@ -105,8 +112,15 @@ function vcat(A::AbstractLinearOperator, B::AbstractLinearOperator)
     vcat_ctprod!(res, adjoint(A), adjoint(B), Anrow, Anrow + Bnrow, w, α, β)
   args5 = (has_args5(A) && has_args5(B))
   S = promote_type(storage_type(A), storage_type(B))
-  isconcretetype(S) ||
-    throw(LinearOperatorException("storage types cannot be promoted to a concrete type"))
+  if !isconcretetype(S)
+    if isconcretetype(storage_type(A))
+      S = storage_type(A)
+    elseif isconcretetype(storage_type(B))
+      S = storage_type(B)
+    else
+      S = Vector{T}
+    end
+  end
   CompositeLinearOperator(T, nrow, ncol, false, false, prod!, tprod!, ctprod!, args5, S = S)
 end
 

src/operations.jl

@@ -140,8 +140,15 @@ function *(op1::AbstractLinearOperator, op2::AbstractLinearOperator)
     throw(LinearOperatorException("shape mismatch"))
   end
   S = promote_type(storage_type(op1), storage_type(op2))
-  isconcretetype(S) ||
-    throw(LinearOperatorException("storage types cannot be promoted to a concrete type"))
+  if !isconcretetype(S)
+    if isconcretetype(storage_type(op1))
+      S = storage_type(op1)
+    elseif isconcretetype(storage_type(op2))
+      S = storage_type(op2)
+    else
+      S = Vector{T}
+    end
+  end
   #tmp vector for products
   vtmp = fill!(S(undef, m2), zero(T))
   utmp = fill!(S(undef, n1), zero(T))
@@ -211,8 +218,15 @@ function +(op1::AbstractLinearOperator, op2::AbstractLinearOperator)
   herm = (ishermitian(op1) && ishermitian(op2))
   args5 = (has_args5(op1) && has_args5(op2))
   S = promote_type(storage_type(op1), storage_type(op2))
-  isconcretetype(S) ||
-    throw(LinearOperatorException("storage types cannot be promoted to a concrete type"))
+  if !isconcretetype(S)
+    if isconcretetype(storage_type(op1))
+      S = storage_type(op1)
+    elseif isconcretetype(storage_type(op2))
+      S = storage_type(op2)
+    else
+      S = Vector{T}
+    end
+  end
   return CompositeLinearOperator(T, m1, n1, symm, herm, prod!, tprod!, ctprod!, args5, S = S)
 end