Paul Eggert wrote on 2015-05-25: > > the regexp is ambiguous > > and does not conform to POSIX, which says the following about RE > > bracket expressions: "To use a <hyphen> as the starting range point, > > it shall either come first in the bracket expression or be specified > > as a collating symbol; for example, "[][.-.]-0]", which matches either > > a <right-square-bracket> or any character or collating element that > > collates between <hyphen> and 0, inclusive." > > <http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_03_05> > > > > In your correspondent's example, the hyphen is a starting range point > > but is neither first in the bracket expression nor is specified as a > > collating symbol, so the regexp doesn't conform to POSIX.
Is there some realistic possibility that the POSIX regex syntax might be extended in the future, in such a way that [^0-9---] means something different? If that happens, and if we opt now to assign a meaning to this regex, we would have to choose between POSIX compliance and backward compatibility — a bad situation. Bruno
