Question

Is there any native library in STL which is tested and works without any extra compiler options?
I tried to use <regex>, but the compiler outputs this:

In file included from /usr/include/c++/4.3/regex:40, from main.cpp:5:
/usr/include/c++/4.3/c++0x_warning.h:36:2: error: #error This file requires compiler and library support for the upcoming ISO C++ standard, C++0x. This support is currently experimental, and must be enabled with the -std=c++0x or -std=gnu++0x compiler options.

Answer 1

G++ 4.3 (and presumably later versions as well) is just being careful about the header files for maximum standards conformance.

If you’re programming in C++98 (the current standard that’s been around for a while), then regular expression support was added in tech report 1, and the and the header files are in a special tr1 directory, and the contents are in a special namespace std::tr1.

In the new C++0x standard, the regular expression support has been merged into the standard library, so it can be found in the header regex and namespace std.

G++ makes sure that you use the right version for the --std= version you specified on the command line, even though internally they’re both the same implementation.

So to make regex work without switching to --std=c++0x, just

#include <tr1/regex>