[#debug_parsing_error]
[section debug_parsing_error]

[h1 Synopsis]

  template <class P, class S>
  struct debug_parsing_error
  {
    debug_parsing_error();
  };

This is a template class.

[table Arguments
  [[Name] [Type]]
  [[`P`]  [[link parser parser]]]
  [[`S`]  [[link string string]]]
]

[h1 Description]

Utility to debug errors generated by a compile-time parser. An instance of the
instantiated template class has to be created and initialised using the default
constructor. When parsing the input string using the parser generates an error,
the default constructor of `debug_parsing_error` prints the error message to the
standard output at run-time and calls `exit`.

[note
Note that more powerful debugging utilities, like
[@https://github.com/sabel83/metashell#metashell Metashell] are also
available.
]

[h1 Header]

  #include <boost/metaparse/debug_parsing_error.hpp>

[h1 Expression semantics]

For any `p` compile-time parser and `s` compile-time string

  debug_parsing_error<p, s>()

Tries to parse `s` using `p` at compile-time. At run-time the constructor
prints the result of parsing to the standard output and calls `exit`.

[h1 Example]

  #include <boost/metaparse/debug_parsing_error.hpp>
  #include <boost/metaparse/int_.hpp>
  #include <boost/metaparse/string.hpp>
  
  #include <type_traits>
  
  using namespace boost::metaparse;
  
  debug_parsing_error<int_, BOOST_METAPARSE_STRING("not an int")> do_debugging;
  
  int main() {}

By running the compiled executable you get the following:

Compile-time parsing results
----------------------------
Input text:
not an int

Parsing failed:
line 1, col 1: Digit expected

[endsect]