--- a/diffOp.jl	Mon Dec 17 12:44:02 2018 +0100
+++ b/diffOp.jl	Mon Dec 17 12:45:30 2018 +0100
@@ -0,0 +1,33 @@
+abstract type DiffOp end
+
+function apply(D::DiffOp, v::AbstractVector) where N
+    error("not implemented")
+end
+
+function innerProduct(D::DiffOp, u::AbstractVector, v::AbstractVector)::Real
+    error("not implemented")
+end
+
+function matrixRepresentation(D::DiffOp)
+    error("not implemented")
+end
+
+function boundaryCondition(D::DiffOp)
+    error("not implemented")
+end
+
+function interface(Du::DiffOp, Dv::DiffOp, b::BoundaryID; type)
+    error("not implemented")
+end
+
+
+# Differential operator for a*d^2/dx^2
+struct Laplace1D <: DiffOp
+    grid
+    a
+    op
+end
+
+function apply(L::Laplace, v::AbstractVector)::AbstractVector
+
+end