Caution
	C++20 module support is on early stage, targets, flags and behavior may change in the future

If using modern CMake define CMake option -DBOOST_USE_MODULES=1 to build a C++20 module and make the Boost::lexical_cast CMake target provide it. After that an explicit usage of C++20 module boost.lexical_cast is allowed:

import boost.lexical_cast;

int main() {
    return boost::lexical_cast<int>("0");
}

The Boost::lexical_cast CMake target gives an ability to mix includes and imports of the library in different translation units. Moreover, if BOOST_USE_MODULES macro is defined then all the boost/lexical_cast... includes implicitly do import boost.lexical_cast; to give all the benefits of modules without changing the existing code.

	Note
	For better compile times make sure that import std; is available when building the boost.lexical_cast module (in CMake logs there should be a 'Using import std;' message).

If not using CMake, then the module could be build manually from the modules/boost_lexical_cast.cppm file.

For manual module build the following commands could be used for clang compiler:

cd lexical_cast/modules
clang++ -I ../include -std=c++20 --precompile -x c++-module boost_lexical_cast.cppm

After that, the module could be used in the following way:

clang++ -std=c++20 -fmodule-file=boost_lexical_cast.pcm boost_lexical_cast.pcm usage_sample.cpp