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Bug introduced in 10.3 and fixed in 10.4

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Just checking whether anyone else can replicate this, or if it's a problem on my computer. The following refuses to execute on my machine, 10.3.1:

Take[{{1}}, All, {UpTo@3}]

It results in General::nomem and Throw::sysexc.

The behaviour seems to be for UpTo[anything bigger than 3], but not for 2.

The intended behaviour would be for it to output {{}}, analogously with

Take[{{1, 2, 3, 4}, {1, 2, 3, 4, 5}, {1}, {1, 2, 3}}, All, {UpTo@2}]

which outputs {{2}, {2}, {}, {2}}.

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  • $\begingroup$ Your syntax is incorrect. The last list demands an integer value and UpTo[3] does not have such a form. What are you trying to accomplish? This works: Take[{{1, 2, 3, 4, 5}}, All, {UpTo[3]}]. $\endgroup$ – David G. Stork Jan 2 '16 at 0:18
  • $\begingroup$ I'm using the fact that Take[{{1, 2, 3, 4}, {1, 2, 3, 4, 5}, {1}, {1, 2, 3}}, All, {UpTo@2}] outputs {{2}, {2}, {}, {2}}, for instance. I could just use Take[{{1}}, All, UpTo@3] and trim down the lists as necessary, but this way was working for when I constructed my prototype using data that let me have 2 instead of 3. $\endgroup$ – Patrick Stevens Jan 2 '16 at 0:20
  • $\begingroup$ @DavidG.Stork Do you get the out-of-memory on my example? Since it works when {1} is Range[5], I'm very surprised it "runs out of memory" if you make the input smaller. $\endgroup$ – Patrick Stevens Jan 2 '16 at 0:22
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    $\begingroup$ This is a bug which has already been fixed in the development version (this example returns unevaluated with an error message). $\endgroup$ – ilian Jan 2 '16 at 0:40
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    $\begingroup$ @PatrickStevens {UpTo[n]} effectively means {UpTo[n], UpTo[n]} and in a sequence specification {m1, m2} only the second position allows UpTo. It would be confusing in the first position. $\endgroup$ – ilian Jan 2 '16 at 0:47
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Turning my comment into an answer, this bug has been fixed as of Mathematica 10.4.0.

Take[{{1}}, All, {UpTo@3}]

During evaluation of Take::seqs: Sequence specification (+n, -n, {+n}, {-n}, {m, n}, 
or {m, n, s}) expected at position 3 in Take[{{1}},All,{UpTo[3]}]. >>

(* Take[{{1}}, All, {UpTo[3]}] *)
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I indeed got the out-of-memory error in your original example.

This works:

Take[{{1}}, All, UpTo@3]

I think putting the last argument in braces makes Mathematica assume that its contents is an integer, but UpTo[3] is not an integer.

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  • $\begingroup$ To make the output exactly what I wanted: If[Length[#] >= 3, Take[#, {3}], {}] & /@ Take[{{1, 2, 3, 4}, {1, 2, 3, 4, 5}, {1}, {1, 2, 3}}, All, UpTo@3] doesn't have the error. $\endgroup$ – Patrick Stevens Jan 2 '16 at 0:30

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