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[/
Copyright 2006-2007 John Maddock.
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt).
]
[section:leftmost_longest_rule The Leftmost Longest Rule]
Often there is more than one way of matching a regular expression at a
particular location, for POSIX basic and extended regular expressions,
the "best" match is determined as follows:
# Find the leftmost match, if there is only one match possible at
this location then return it.
# Find the longest of the possible matches, along with any ties.
If there is only one such possible match then return it.
# If there are no marked sub-expressions, then all the remaining
alternatives are indistinguishable; return the first of these found.
# Find the match which has matched the first sub-expression in the
leftmost position, along with any ties. If there is only on such
match possible then return it.
# Find the match which has the longest match for the first sub-expression,
along with any ties. If there is only one such match then return it.
# Repeat steps 4 and 5 for each additional marked sub-expression.
# If there is still more than one possible match remaining, then they are
indistinguishable; return the first one found.
[endsect]
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