Checks if expr is a scalar. This is the case if expr is algebraic and not a Vector or Matrix.

More precisely, expr is a scalar if:

expr is of type algebraic, and

expr is not the name of a procedure, table, or module, and

if the top-level type of expr is one of `*`, `+`, `.`, `^`, `&*`, `&+`, and `&^` (that is, if op(0, expr) is one of these operators), then all its arguments are scalars.

$a≔\mathrm{table}\left(\left['\mathrm{apple}'=3\,'\mathrm{orange}'=5\right]\right)$

$a≔table\left(\left[\mathrm{apple}=3\,\mathrm{orange}=5\right]\right)$

$\mathrm{type}\left(a\,\mathrm{scalar}\right)$

$\mathrm{false}$

$\mathrm{type}\left(x\,\mathrm{scalar}\right)$

$\mathrm{true}$

$\mathrm{type}\left(42\,\mathrm{scalar}\right)$

$\mathrm{true}$

$\mathrm{type}\left(\sin \,\mathrm{scalar}\right)$

$\mathrm{false}$

$\mathrm{type}\left(x·y\,\mathrm{scalar}\right)$

$\mathrm{true}$

$v≔\mathrm{Vector}\left(\left[1\,2\,3\right]\right)$

$v≔\left[\begin{array}{c}1\\ 2\\ 3\end{array}\right]$

$\mathrm{type}\left(x·v\,\mathrm{scalar}\right)$

$\mathrm{false}$