Apply a list of functions to each level in a nested parse table.
pre_visit() applies funs before it proceeds to the children,
(that is, starts from the outermost level of nesting progressing
to the innermost level), post_visit() proceeds to its children
before applying the functions (meaning it first applies the functions
to the innermost level of nesting first and then going outwards).
pre_visit(pd_nested, funs)pre_visit_one(pd_nested, fun)
post_visit(pd_nested, funs)
post_visit_one(pd_nested, fun)
A nested parse table.
A list of transformer functions.
Other visitors:
visit_one()