Create a decorated interval from a bare interval.
The decorated interval will carry the best possible decoration, i. e.,
trv for empty intervals, dac for unbound intervals, and
com for common intervals.
If X already is decorated, nothing happens. In particular, the decoration will not be changed in order to not lose any information.
newdec (infsup (2, 3)) ⇒ ans = [2, 3]_com
See also: @infsupdec/infsupdec.
Package: interval