The Dimensions(M) function returns the equivalent of [rtable_dims(M)], but works on lists as well.

When M is a scalar the result will always be [ 1..1 ].

This function is part of the ArrayTools package, so it can be used in the short form Dimensions(..) only after executing the command with(ArrayTools).  However, it can always be accessed through the long form of the command by using ArrayTools[Dimensions](..).

$\mathrm{with}\left(\mathrm{ArrayTools}\right)\:$

$\mathrm{Dimensions}\left(\left[\left[1\,2\right]\,\left[3\,4\right]\right]\right)$

$\left[1..2\,1..2\right]$