NotebookGetExpression

[Nowak Robert <Robert.Nowak@XXXXXXX.at>]

Liebe MMA user vielleicht fällt euch hierzu etwas ein.



Dear all !

I am looking for a way how to revert to an expensive (processing time)
evaluated expression.

I would like to have a notebook (or package) containing the expression
in question which should be reevaluated only on a manual request and
otherwise the once preevaluated expression should be used.

Any hints on how this could be achieved simpler ?
I found the following solution:

(*---------------------------------------------------------------------------------------------------
*)

(* get the expression of the preceding cell *)
NotebookGetExpression[] := Module[{nb, e},
       nb = SelectedNotebook[];
       SelectionMove[nb, Before, EvaluationCell];
       SelectionMove[nb, Previous, CellContents];
       e = ToExpression@NotebookRead[nb];
       SelectionMove[nb, After, EvaluationCell];
       e
 ]

(* this stands exemplary for an expression expensive to evaluate *)
(* after once evaluated the cell will be marked by hand as non
evaluatable *)
(* would be nice if the non evaluatable marking could be automated *)

Expand[(x + y)^2]

Out[ ]= x^2 + 2 x y + y^2

(* her we get the preceding expression and define a function for it *)
Ex[x_, y_] = NotebookGetExpression[];

(* test the defined function *)
Ex[a, b]

Out[ ]= a^2 + 2 a b + b^2

(*---------------------------------------------------------------------------------------------------
*)

(* CellExpression starting here : *)
{
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  RowBox[{
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Cell[CellGroupData[{

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 RowBox[{"Expand", "[",
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   RowBox[{"(",
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Cell[BoxData[
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}, Open  ]],

Cell[BoxData[
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 "\n",
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  RowBox[{
   RowBox[{"Ex", "[",
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Cell[BoxData[
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}, Open  ]]
}