# Special value for truncation:
# l Allow left truncation if ? is at left side of term.
# r Allow right truncation if ? is at left side of term.
# b Allow left&right truncation if ? is at left&right side of term.
# n Set truncation explicitly to "none" if no ? is given.
# Special value for truncation:
# l Allow left truncation if ? is at left side of term.
# r Allow right truncation if ? is at left side of term.
# b Allow left&right truncation if ? is at left&right side of term.
# n Set truncation explicitly to "none" if no ? is given.