The
sub_match object stored at index 0 represents sub-expression 0,
i.e., the whole match
. In this case the
sub_match member
matched is always
true. The
sub_match
object stored at index
n denotes what matched the marked
sub-expression
n within the matched expression
. If the
sub-expression
n participated in a regular expression
match then the
sub_match member
matched evaluates to
true, and
members
first and
second denote the range of characters
[
first, second) which formed that
match
. Otherwise
matched is
false, and members
first
and
second point to the end of the sequence
that was searched
. [
Note 1:
The
sub_match objects representing
different sub-expressions that did not participate in a regular expression
match need not be distinct
. —
end note]