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- [/
- / Copyright (c) 2008 Eric Niebler
- /
- / 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 Appendix 3: Differences from Boost.Regex]
- Since many of xpressive's users are likely to be familiar with the _regexpp_ library,
- I would be remiss if I failed to point out some important differences between xpressive
- and _regexpp_. In particular:\n
- * `xpressive::basic_regex<>` is a template on the iterator type, not the character type.
- * `xpressive::basic_regex<>` cannot be constructed directly from a string; rather, you must use
- `basic_regex::compile()` or `regex_compiler<>` to build a regex object from a string.
- * `xpressive::basic_regex<>` does not have an `imbue()` member function; rather, the `imbue()` member
- function is in the `xpressive::regex_compiler<>` factory.
- * `boost::basic_regex<>` has a subset of `std::basic_string<>`'s members. `xpressive::basic_regex<>`
- does not. The members lacking are: `assign()`, `operator[]()`, `max_size()`, `begin()`, `end()`,
- `size()`, `compare()`, and `operator=(std::basic_string<>)`.
- * Other member functions that exist in `boost::basic_regex<>` but do not exist in
- `xpressive::basic_regex<>` are: `set_expression()`, `get_allocator()`, `imbue()`, `getloc()`,
- `getflags()`, and `str()`.
- * `xpressive::basic_regex<>` does not have a RegexTraits template parameter. Customization of regex
- syntax and localization behavior will be controlled by `regex_compiler<>` and a custom regex facet
- for `std::locale`.
- * `xpressive::basic_regex<>` and `xpressive::match_results<>` do not have an Allocator template
- parameter. This is by design.
- * `match_not_dot_null` and `match_not_dot_newline` have moved from the `match_flag_type` enum to the
- `syntax_option_type` enum, and they have changed names to `not_dot_null` and `not_dot_newline`.
- * The following `syntax_option_type` enumeration values are not supported: `escape_in_lists`,
- `char_classes`, `intervals`, `limited_ops`, `newline_alt`, `bk_plus_qm`, `bk_braces`, `bk_parens`,
- `bk_refs`, `bk_vbar`, `use_except`, `failbit`, `literal`, `perlex`, `basic`, `extended`, `emacs`,
- `awk`, `grep` ,`egrep`, `sed`, `JavaScript`, `JScript`.
- * The following `match_flag_type` enumeration values are not supported: `match_not_bob`,
- `match_not_eob`, `match_perl`, `match_posix`, and `match_extra`.
- Also, in the current implementation, the regex algorithms in xpressive will not detect
- pathological behavior and abort by throwing an exception. It is up to you to write efficient
- patterns that do not behave pathologically.
- [endsect]
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