the desired stack element, counting from 0 (i.e.
the desired stack element, counting from 0 (i.e. 0 is the stack top)
Provides a symbolic representation of the StateRef, used for creating feature names.
Provides a symbolic representation of the StateRef, used for creating feature names.
A BreadcrumbRef is a StateRef (see above) whose apply operation returns the breadcrumb of the
index
th element of the stack, if it exists.the desired stack element, counting from 0 (i.e. 0 is the stack top)