Sometimes
you don't have to explicitly quote special characters to make
them ordinary. For instance, most characters lose any special meaning
inside a list (see section 3.6 List Operators ([ ... ] and [^ ... ])). In addition, if the syntax bits
RE_CONTEXT_INVALID_OPS and RE_CONTEXT_INDEP_OPS
aren't set, then (for historical reasons) the matcher considers special
characters ordinary if they are in contexts where the operations they
represent make no sense; for example, then the match-zero-or-more
operator (represented by `*') matches itself in the regular
expression `*foo' because there is no preceding expression on which
it can operate. It is poor practice, however, to depend on this
behavior; if you want a special character to be ordinary outside a list,
it's better to always quote it, regardless.
Regex therefore doesn't consider the `^' to be the first character in the list. If you put a `^' character first in (what you think is) a matching list, you'll turn it into a nonmatching list.
You can't use a character class for the starting or ending point of a range, since a character class is not a single character.
Regular expressions are also referred to as "patterns," hence the name "pattern buffer."
A table that maps all uppercase letters to the corresponding lowercase ones would work just as well for this purpose.
This document was generated on 1 December 1997 using the texi2html translator version 1.51.