add.backtick            Add backtick
dt.calculate            dt.calculate
dt.choose.cols          dt.choose.cols
dt.choose.rows          dt.choose.rows
dt.count.rows           dt.count.rows
dt.define.variable      dt.define.variable
dt.first.k.rows         dt.first.k.rows
dt.last.k.rows          dt.last.k.rows
dt.remove.variables     dt.remove.variables
dt.sort                 dt.sort
reduce.vector.expression
                        Takes a numeric vector and produces a statement
                        with a more compact representation.  For
                        instance, c(1,2,3,4) would become '1:4' and
                        c(1:3, 4:6) could become '1:6'.
