improve type inference in laplacian (#207)

Author: jishnub

src/PDE/KroneckerOperator.jl

@@ -254,7 +254,7 @@ Base.transpose(S::ConstantTimesOperator) = sp.c*transpose(S.op)
 ### Calculus
 
 #TODO: general dimension
-function Derivative(S::TensorSpace{SV,DD},order::Vector{Int}) where {SV,DD<:EuclideanDomain{2}}
+function Derivative(S::TensorSpace{SV,DD}, order) where {SV,DD<:EuclideanDomain{2}}
     @assert length(order)==2
     if order[1]==0
         Dy=Derivative(S.spaces[2],order[2])

src/PDE/PDE.jl

@@ -10,8 +10,8 @@ lap(f::Fun) = Laplacian()*f
 
 
 function Laplacian(d::BivariateSpace,k::Integer)
-    Dx2=Derivative(d,[2,0])
-    Dy2=Derivative(d,[0,2])
+    Dx2=Derivative(d, Vec{2}(2,0))
+    Dy2=Derivative(d, Vec{2}(0,2))
     if k==1
         LaplacianWrapper(Dx2+Dy2,k)
     else