--- a/src/Grids/grid.jl	Fri Feb 10 08:36:56 2023 +0100
+++ b/src/Grids/grid.jl	Sat Feb 18 11:37:35 2023 +0100
@@ -1,27 +1,76 @@
 """
-     Grid
+     Grid{T,D,RD} <: AbstractArray{T,D}
+
+The top level type for grids.
 
 Should implement
-    Base.ndims(grid::Grid)
-    points(grid::Grid)
+# TBD:
+"""
+#TBD: Does all the kinds of grids we want fit with this interface?
+# Multigrid?
+# Unstructured?
+# Triangular structured grids?
+# Non-simply connected?
+#
+# Maybe it shouldn't be an abstract array after all?
+abstract type Grid{T,D,RD} <: AbstractArray{T,D} end
+
+
+Base.ndims(::Grid{T,D,RD}) where {T,D,RD} = D # nidms borde nog vara antalet index som används för att indexera nätet. Snarare än vilken dimension nätet har (tänk ostrukturerat)
+nrangedims(::Grid{T,D,RD}) where {T,D,RD} = RD
+Base.eltype(::Grid{T,D,RD}) where {T,D,RD} = T # vad ska eltype vara? Inte T väl... en vektor? SVector{T,D}?
+
+function eval_on(::Grid) end # TODO: Should return a LazyArray and index the grid
+function refine(::Grid) end
+function coarsen(::Grid) end # Should this be here? What if it is not possible?
+
+abstract type BoundaryId end
 
 """
-abstract type Grid end
-function points end
+# TODO
+"""
+function boundary_identifiers(::Grid) end
+"""
+# TODO
+"""
+function boundary_grid(::Grid, ::BoundaryId) end
+
+
+# TODO: Make sure that all grids implement all of the above.
 
 """
     dims(grid::Grid)
 
-A range containing the dimensions of `grid`
+Enumerate the dimensions of the grid.
 """
 dims(grid::Grid) = 1:ndims(grid)
 
+
+
+# TBD: New file grid_functions.jl?
+
 """
-    evalOn(grid::Grid, f::Function)
+    getcomponent(gfun, I::Vararg{Int})
 
-Evaluate function `f` on `grid`
+Return one of the components of gfun as a grid function.
 """
-function evalOn(grid::Grid, f::Function)
-    F(x) = f(x...)
-    return F.(points(grid))
+# Should it be lazy? Could it be a view?
+function getcomponent(gfun, I::Vararg{Int}) end
+# function getcomponent(gfun, s::Symbol) end ?
+
+# TBD: New file zero_dim_grid.jl?
+struct ZeroDimGrid{T,S,RD} <: Grid{T,0,RD}
+    p::S
+
+    function ZeroDimGrid(p)
+        T = eltype(p)
+        S = typeof(p)
+        RD = length(p)
+        return new{T,S,RD}(p)
+    end
 end
+
+Base.size(g::ZeroDimGrid) = ()
+Base.getindex(g::ZeroDimGrid) = g.p
+Base.eachindex(g::ZeroDimGrid) = CartesianIndices(())
+