Add support for linear indexing (#19)

Project.toml

@@ -1,7 +1,7 @@
 name = "Derive"
 uuid = "a07dfc7f-7d04-4eb5-84cc-a97f051f655a"
 authors = ["ITensor developers <[email protected]> and contributors"]
-version = "0.3.5"
+version = "0.3.6"
 
 [deps]
 Adapt = "79e6a3ab-5dfb-504d-930d-738a2a938a0e"

src/abstractarrayinterface.jl

@@ -44,13 +44,27 @@ end
   return @interface interface getindex(a, Tuple(I)...)
 end
 
+# Linear indexing.
+@interface interface ::AbstractArrayInterface function Base.getindex(
+  a::AbstractArray, I::Int
+)
+  return @interface interface getindex(a, CartesianIndices(a)[I])
+end
+
 # TODO: Use `MethodError`?
 @interface ::AbstractArrayInterface function Base.setindex!(
   a::AbstractArray{<:Any,N}, value, I::Vararg{Int,N}
 ) where {N}
   return error("Not implemented.")
 end
 
+# Linear indexing.
+@interface interface ::AbstractArrayInterface function Base.setindex!(
+  a::AbstractArray, value, I::Int
+)
+  return @interface interface setindex!(a, value, CartesianIndices(a)[I])
+end
+
 # TODO: Make this more general, use `Base.to_index`.
 @interface interface::AbstractArrayInterface function Base.setindex!(
   a::AbstractArray{<:Any,N}, value, I::CartesianIndex{N}