some fixes

Author: ChrisRackauckas

docs/src/tutorials/operator_algebras.md

@@ -13,9 +13,13 @@ function f(w, v, u, p, t)
     w .= u .* v
 end
 
+u = rand(4)
+p = nothing # parameter struct
+t = 0.0     # time
+
 M = MatrixOperator(rand(N, N))
 D = DiagonalOperator(rand(N))
-F = FunctionOperator(f, zeros(N), zeros(N))
+F = FunctionOperator(f, zeros(N), zeros(N); u, p, t)
 ```
 
 Then, the following codes just work.
@@ -31,15 +35,9 @@ L5 = [M; D]' * [M F; F D] * [F; D]
 Each `L#` can be applied to `AbstractVector`s of appropriate sizes:
 
 ```@example operator_algebra
-p = nothing # parameter struct
-t = 0.0     # time
-
-u = rand(N)
 v = rand(N)
 w = L1(v, u, p, t) # == L1 * v
 
-L3 = cache_operator(L3, v)
-
 v_kron = rand(N^3)
 w_kron = L3(v_kron, u, p, t) # == L3 * v_kron
 ```