Manual

Chapter 10: C++ Language Interface 105
To encapsulate the coordination with the Flex scanner, it is useful to have two members
function to open and close the scanning phase. members.
// Handling the scanner.
void scan_begin ();
void scan_end ();
bool trace_scanning;
Similarly for the parser itself.
// Handling the parser.
void parse (const std::string& f);
std::string file;
bool trace_parsing;
To demonstrate pure handling of parse errors, instead of simply dumping them on the
standard error output, we will pass them to the compiler driver using the following two
member functions. Finally, we close the class declaration and CPP guard.
// Error handling.
void error (const yy::location& l, const std::string& m);
void error (const std::string& m);
};
#endif // ! CALCXX_DRIVER_HH
The implementation of the driver is straightforward. The parse member function deserves
some attention. The error functions are simple stubs, they should actually register
the located error messages and set error state.
#include "calc++-driver.hh"
#include "calc++-parser.hh"
calcxx_driver::calcxx_driver ()
: trace_scanning (false), trace_parsing (false)
{
variables["one"] = 1;
variables["two"] = 2;
}
calcxx_driver::~calcxx_driver ()
{
}
void
calcxx_driver::parse (const std::string &f)
{
file = f;
scan_begin ();
yy::calcxx_parser parser (*this);
parser.set_debug_level (trace_parsing);
parser.parse ();
scan_end ();