The function type/listlist returns true if expr is a nonempty list of lists, with each inner list having the same number of elements. Otherwise, it returns false.

If a type is given, then an additional check will be made to ensure that all the operands of the inner lists are of the given type.

type/nonemptylist

$\mathrm{type}\left(\left[\right]\,'\mathrm{listlist}'\right)$

$\mathrm{false}$

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

$\mathrm{true}$

$\mathrm{type}\left(\left[\left[1\,2\right]\,\left[3\,4\right]\right]\,'\mathrm{listlist}\left(\mathrm{integer}\right)'\right)$

$\mathrm{true}$

$\mathrm{type}\left(\left[8\,7\,6\,12\right]\,'\mathrm{listlist}'\right)$

$\mathrm{false}$

$\mathrm{type}\left(\left[\left[1\,2\right]\,\left[3\,4\,5\right]\right]\,'\mathrm{listlist}'\right)$

$\mathrm{false}$

$\mathrm{type}\left(\left[\left[\right]\right]\,'\mathrm{listlist}'\right)$

$\mathrm{true}$

$\mathrm{type}\left(\left[\left[\left[a\right]\,\left[b\right]\right]\,\left[\left[c\right]\,\left[d\right]\right]\right]\,'\mathrm{listlist}'\right)$

$\mathrm{true}$

$\mathrm{type}\left(\left[\left[\left[a\right]\,\left[b\right]\right]\,\left[\left[c\right]\,\left[d\right]\right]\right]\,'\mathrm{listlist}\left(\mathrm{integer}\right)'\right)$

$\mathrm{false}$