Source code is available on Github . The documentation is here . Quote from the blog :
C ++ Now 2015. Today is the official release of Spirit X3, aka Spirit 3.0.0. X3 will be in beta, coexisting alongside Qi, Karma, Lex and Classic.
According to Sehe (see comments), the X3 was included in the Boost release, at least as far back as November 2015. Since it's only a title, I suppose you could just as easily download Spirit from Github.
If you look in the "Include" section of the documentation (see above), you will read:
Spirit is just a heading library. There are no libraries to link to. To use Spirit X3, simply enable:
SPIRIT_X3_VERSION This is a hexadecimal number where the first two digits identify the major version, while the last two digits identify the minor version. For instance:
#define SPIRIT_VERSION 0x3000
Take a look at Github and you will find include/boost/spirit/home/x3 . If you check the pull query history, you will see that the project is very lively. If you have doubts about the activity of the project, contact the team.
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