REG_NEWLINE Compile for newline-sensitive matching. By default,
newline is a completely ordinary character with no special meaning in
either REs or strings. With this flag, `[^' bracket expressions and
`.' never match newline, a `^' anchor matches the null string after
any newline in the string in addition to its normal function, and the
`$' anchor matches the null string before any newline in the string
in addition to its normal function.
Using ^ and $ to match near newlines makes matching patterns that
cross
lines much easier to control. But anchors are also a source of bugs
for
some implementations, e.g. libtre.
Maybe I underestimated the utility of ^ and $. The definition seems
intricate. I thought about adding a combinator for matching newline
but now think that would lead to wrong start and end positions. For
example the start position of the matching substring for ^a in "a
\na" should be 2 not 1, right? Or is it 0 although there is no
newline at the beginning?
Is there a page with examples that show how ^ and $ should behave
exactly?
Sebastian
--
Underestimating the novelty of the future is a time-honored tradition.
(D.G.)
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