3
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Is there a special keyword to get the current index in Scan ?
For example, let say I have the following code :

Scan[Print[#] &, {2, 5, 7}]

It print the content of the list :

2
5
7

How to modify the code to print the current index also ?

1,2
2,5
3,7
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1
  • $\begingroup$ This question has essentially the same answer as this one. Should it be tagged as a duplicate? $\endgroup$
    – m_goldberg
    Aug 20, 2014 at 9:40

2 Answers 2

5
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MapIndexed[Print[Row[{First@#2, #1}, ","]] &, {2, 5, 7}];
1,2
2,5
3,7

Or simpler:

MapIndexed[Print[First@#2, ",", #1] &, {2, 5, 7}]
1,2
2,5
3,7
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8
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A scan operation doesn't really have an index, but you can get the effect you want by introducing a counter.

Module[{i = 0}, Scan[(i++; Print[i, ", ", #]) &, {2, 5, 7}]]

output

You might also consider using Do, which does have an index.

With[{data = {2, 5, 7}}, 
  Do[Print[i, ", ", data[[i]]], {i, Length @ data}]]
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