Get the unevaluated expression from a numbered cell

Question

If a cell exists as below:

In[1] := (xyPoints = {{1,2},{2,5},{3,10}}; ListLinePlot[xyPoints])

Is it possible to get at the expression rather than the plot shown in Out[1]. In other words, can I somehow get the held CompoundExpression in In[1] rather than the evaluated plot?

Awesome. Looks like I can use something like: DownValues[In][[1]] /. RuleDelayed[x_, y_] :> HoldComplete[y] — teedr, Aug 13 '13 at 22:17
Interestingly, this does not work if there is a newline after the semicolon. — teedr, Aug 13 '13 at 22:38
You could also use Information[In] or ToExpression[InString[1], StandardForm, Hold] — Alexey Popkov, Aug 14 '13 at 02:12
Related: https://mathematica.stackexchange.com/questions/111963/is-it-possible-to-retrieve-a-previous-un-evaluated-un-normalized-input/164312#164312 — Jess Riedel, Aug 08 '19 at 22:49

score 5 · Accepted Answer · answered Aug 14 '13 at 02:12

5

You could use InString for that:

ToExpression[InString[1], StandardForm, Hold]

Hold[xyPoints = {{1, 2}, {2, 5}, {3, 10}}; ListLinePlot[xyPoints]]

answered Aug 14 '13 at 02:12

Alexey Popkov

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Great. Do you know if there a way to get all the lines in a cell? If a compound expression is spread over multiple lines, each line seems to correspond to a different In[x] number. – teedr Aug 14 '13 at 17:51
@teedr You could try to experiment with DownValues[InString] for that. – Alexey Popkov Aug 14 '13 at 21:41
In addition to the problem with multiple lines, this answer will not retain all the 2D input formatting that your original cell might have had. That means you cannot use this answer to recover exactly what you had in an input cell that you, say, accidentally deleted. To recover everything, use Carl Woll's answer to a related question. – Jess Riedel Aug 08 '19 at 22:47

score 3 · Answer 2 · answered Aug 13 '13 at 22:12

3

Cells[CellLabel -> "In[1]:="] // First // NotebookRead // 
  First // MakeExpression

gives

HoldComplete[xyPoints = {{1, 2}, {2, 5}, {3, 10}}; 
 ListLinePlot[xyPoints]]

answered Aug 13 '13 at 22:12

Rolf Mertig

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Get the unevaluated expression from a numbered cell

2 Answers2