Recognizing and suppressing invisible output to j

[MichaelChirico]

This is derived from this topic on SO. Here's the example:

set.seed(120834)
DT <- data.table(var = rnorm(100))

The following returns the hist object invisibly (as can be readily seen from hist.default code):

hist(DT[ , var])

However, when hist is called within j (which feels more natural to me), it appears the hist object is returned invisibly within j, then j returns visibly:

DT[ , hist(var)]
$breaks
 [1] -3.0 -2.5 -2.0 -1.5 -1.0 -0.5  0.0  0.5  1.0  1.5  2.0  2.5

$counts
 [1]  1  1  6  7 16 20 20 12 12  3  2

$density
 [1] 0.02 0.02 0.12 0.14 0.32 0.40 0.40 0.24 0.24 0.06 0.04

$mids
 [1] -2.75 -2.25 -1.75 -1.25 -0.75 -0.25  0.25  0.75  1.25  1.75  2.25

$xname
[1] "var"

$equidist
[1] TRUE

attr(,"class")
[1] "histogram"

However, I noticed that this is not an issue for with, which, if I'm understanding correctly, should be going through the same procedure: with(DT, hist(var)) returns the hist object invisibly.

Is there any way to get j to recognize when it's been returned an object invisibly and to pass this through to the console? The alternative (always suppressing j output) is too blunt a tool.

[MichaelChirico]

Closing as identical to #482.