boost regex exception thrown from constructor for .*{

Question

Boost version 1.60.0 gcc 4.8.4

When I construct a boost::regex object with the string: .*{ I get an exception stating that:

what():  Missing } in quantified repetition.  The error occurred while parsing the regular expresion: '.*{>>>HERE>>>'.

This error occurs when the object is a boost::regex::extended type, but not if it is boost::regex::perl .

So the following throws the exception:

regString(".*{");
boost::regex reg_e(regString, boost::regex::extended);

but this does not:

regString(".*{");
boost::regex reg_p(regString, boost::regex::perl);

Is this expected behavior or a bug?
If it is expected, why? and what is an appropriate work around?

Answer 1

{ is a special character in this context , you need to escape it.

http://www.boost.org/doc/libs/1_60_0/libs/regex/doc/html/boost_regex/syntax/perl_syntax.html

Note that the "{" and "}" characters will treated as ordinary literals when used in a context that is not a repeat: this matches Perl 5.x behavior. For example in the expressions "ab{1", "ab1}" and "a{b}c" the curly brackets are all treated as literals and no error will be raised.