Following is a sample session using the stack abstraction of Section 7.1.
s =: make_stack '' stackp s 1 NB. s is a stack empty_stackp s 1 s =: push_stack 1 2 3 ; s NB. Push the list 1 2 3 on s top_stack s 1 2 3 empty_stackp s 0 NB. s is not empty now s =: push_stack 'Some text' ; s NB. Push a char string on s top_stack s Some text s =: pop_stack s top_stack s 1 2 3 s =: pop_stack s empty_stackp s 1 NB. s is empty again