1[/ 2 / Copyright (c) 2008 Eric Niebler 3 / 4 / Distributed under the Boost Software License, Version 1.0. (See accompanying 5 / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 6 /] 7 8[section Appendix 3: Differences from Boost.Regex] 9 10Since many of xpressive's users are likely to be familiar with the _regexpp_ library, 11I would be remiss if I failed to point out some important differences between xpressive 12and _regexpp_. In particular:\n 13 14* `xpressive::basic_regex<>` is a template on the iterator type, not the character type. 15* `xpressive::basic_regex<>` cannot be constructed directly from a string; rather, you must use 16 `basic_regex::compile()` or `regex_compiler<>` to build a regex object from a string. 17* `xpressive::basic_regex<>` does not have an `imbue()` member function; rather, the `imbue()` member 18 function is in the `xpressive::regex_compiler<>` factory. 19* `boost::basic_regex<>` has a subset of `std::basic_string<>`'s members. `xpressive::basic_regex<>` 20 does not. The members lacking are: `assign()`, `operator[]()`, `max_size()`, `begin()`, `end()`, 21 `size()`, `compare()`, and `operator=(std::basic_string<>)`. 22* Other member functions that exist in `boost::basic_regex<>` but do not exist in 23 `xpressive::basic_regex<>` are: `set_expression()`, `get_allocator()`, `imbue()`, `getloc()`, 24 `getflags()`, and `str()`. 25* `xpressive::basic_regex<>` does not have a RegexTraits template parameter. Customization of regex 26 syntax and localization behavior will be controlled by `regex_compiler<>` and a custom regex facet 27 for `std::locale`. 28* `xpressive::basic_regex<>` and `xpressive::match_results<>` do not have an Allocator template 29 parameter. This is by design. 30* `match_not_dot_null` and `match_not_dot_newline` have moved from the `match_flag_type` enum to the 31 `syntax_option_type` enum, and they have changed names to `not_dot_null` and `not_dot_newline`. 32* The following `syntax_option_type` enumeration values are not supported: `escape_in_lists`, 33 `char_classes`, `intervals`, `limited_ops`, `newline_alt`, `bk_plus_qm`, `bk_braces`, `bk_parens`, 34 `bk_refs`, `bk_vbar`, `use_except`, `failbit`, `literal`, `perlex`, `basic`, `extended`, `emacs`, 35 `awk`, `grep` ,`egrep`, `sed`, `JavaScript`, `JScript`. 36* The following `match_flag_type` enumeration values are not supported: `match_not_bob`, 37 `match_not_eob`, `match_perl`, `match_posix`, and `match_extra`. 38 39Also, in the current implementation, the regex algorithms in xpressive will not detect 40pathological behavior and abort by throwing an exception. It is up to you to write efficient 41patterns that do not behave pathologically. 42 43[endsect] 44