8
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Let's say we have a cell:


(*newline*)
(*newline*)
Plot[
    x, 
    {x, 0, 1}
]
(*newline*)    
Plot[x, {x, 0, 2}]

How to read it expression by expression?

So e.g to read Plots one by one, in whatever form, Boxes, Hold[expression], String?

Here's my attempt:

SelectionMove[PreviousCell[] (*cellobject in general*), All, Cell];

text = First[  FrontEndExecute[
    FrontEnd`ExportPacket[NotebookSelection[], "InputText"]]
]; (*1*)

Module[{stream = StringToStream[text], temp},
   temp = ReadList[stream, Hold[Expression]];
   Close[stream];
   temp
]
{Hold[Plot[x, {x, 0, 1}]], Hold[Plot[x, {x, 0, 2}]]}

Quite long, and problematic because it changes selection.

I think there should be better way since this is what FrontEnd is doing anyway, reading expression by expression:

{
    1, Abort[]
}
2
$Aborted
2

(*1*) - How do I extract the contents of a selected cell as plain text?

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1
  • 1
    $\begingroup$ At least tangentially related: (29264) $\endgroup$
    – Mr.Wizard
    May 9, 2016 at 9:18

2 Answers 2

3
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Instead of SelectionMove and NotebookSelection one can use NotebookRead[PreviousCell[]] and then cleanup the text returned by the ExportPacket.

Thread @ MakeExpression[
 "{" <> 
  StringReplace[
   First[FrontEndExecute[FrontEnd`ExportPacket[NotebookRead[PreviousCell[]], "InputText"]]], 
   {"\r\n " -> "", "\r\n" -> ","}] 
  <> "}", 
 StandardForm] /. HoldComplete[Null] :> Nothing

Output for the two examples:

{HoldComplete[Plot[x, {x, 0, 1}]], HoldComplete[Plot[x, {x, 0, 2}]]}

and

{HoldComplete[{1, Abort[]}], HoldComplete[2]}
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2
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Here is a slight modification of Karsten's answer. Previously I felt it was too similar, but I suppose it cannot hurt to post it. The main difference is that I avoid MakeExpression. I also like the alternative in your question, which is to use StringToStream.

read[cObj_] :=
 DeleteCases[#, HoldComplete[Null]] &@(
   ToExpression[#, InputForm, 
      HoldComplete] & /@
    (StringSplit[#, "\n"] &)@
     First@FrontEndExecute@
       FrontEnd`ExportPacket[NotebookRead@cObj, "PlainText"]
   )
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2
  • $\begingroup$ Not general enough, if you have a cell indentical as my example: {"(*newline*)\r", "(*newline*)\r", "Plot[\r", "x,\r", "{x,0,1}\r", "]\ \r", "(*newline*)\r", "Plot[x,{x,0,2}]"} so StringSplit has to be more careful. $\endgroup$
    – Kuba
    May 4, 2016 at 16:19
  • $\begingroup$ @Kuba hmm thats strange, I thought "\n" caught all newlines on my other computer (OSX). $\endgroup$ May 4, 2016 at 20:23

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