F.2.13 library(dcghighorder)

foreach//2	Generate a list from the solutions of Generator.
foreach//3	Generate a list from the solutions of Generator.
optional//2	Perform an optional match, executing Default if Match is not matched.
sequence//2	Match or generate a sequence of Element.
sequence//3	Match or generate a sequence of Element where each pair of elements is separated by Sep.
sequence//5	Match or generate a sequence of Element enclosed by Start end End, where each pair of elements is separated by Sep.