Important: The stack command has been deprecated. Use the superseding command DEQueue instead.

The call stack[new]() returns an empty stack. The call stack[new](x1, ..., xn) returns a stack with the values x1, ..., xn on the stack with x1 on the top of the stack.

The call stack[push](x, s) puts x on the top of the stack s while stack[pop](s) returns (and removes) the top element from the stack.

The call stack[empty](s) returns true if the stack s is empty, and false if it is not empty.

Additionally, stack[top](s) returns the top element of the stack (but does not remove it) and stack[depth](s) returns the number of elements in the stack.

An object-oriented stack implementation is available via the Stack constructor.

$s≔\mathrm{stack}\left[\mathrm{new}\right]\left(\mathrm{greg}\,\mathrm{tony}\,\mathrm{bruno}\,\mathrm{michael}\right)\:$

$\mathrm{stack}\left[\mathrm{push}\right]\left(\mathrm{stefan}\,s\right)$

$\mathrm{stefan}$

$\mathrm{stack}\left[\mathrm{depth}\right]\left(s\right)$

$5$

$\mathrm{stack}\left[\mathrm{top}\right]\left(s\right)$

$\mathrm{stefan}$

$$\begin{gathered} \mathbf{while}\mathbf{not}\mathrm{stack}\left[\mathrm{empty}\right]\left(s\right)\mathbf{do} \\ \mathrm{stack}\left[\mathrm{pop}\right]\left(s\right) \\ \mathbf{end}\mathbf{do} \end{gathered}$$

$\mathrm{greg}$