ceph/src/boost/libs/metaparse/doc/debug_parsing_error.qbk

   1 [#debug_parsing_error]
   2 [section debug_parsing_error]
   3
   4 [h1 Synopsis]
   5
   6   template <class P, class S>
   7   struct debug_parsing_error
   8   {
   9     debug_parsing_error();
  10   };
  11
  12 This is a template class.
  13
  14 [table Arguments
  15   [[Name] [Type]]
  16   [[`P`]  [[link parser parser]]]
  17   [[`S`]  [[link string string]]]
  18 ]
  19
  20 [h1 Description]
  21
  22 Utility to debug errors generated by a compile-time parser. An instance of the
  23 instantiated template class has to be created and initialised using the default
  24 constructor. When parsing the input string using the parser generates an error,
  25 the default constructor of `debug_parsing_error` prints the error message to the
  26 standard output at run-time and calls `exit`.
  27
  28 [note
  29 Note that more powerful debugging utilities, like
  30 [@https://github.com/sabel83/metashell#metashell Metashell] are also
  31 available.
  32 ]
  33
  34 [h1 Header]
  35
  36   #include <boost/metaparse/debug_parsing_error.hpp>
  37
  38 [h1 Expression semantics]
  39
  40 For any `p` compile-time parser and `s` compile-time string
  41
  42   debug_parsing_error<p, s>()
  43
  44 Tries to parse `s` using `p` at compile-time. At run-time the constructor
  45 prints the result of parsing to the standard output and calls `exit`.
  46
  47 [h1 Example]
  48
  49   #include <boost/metaparse/debug_parsing_error.hpp>
  50   #include <boost/metaparse/int_.hpp>
  51   #include <boost/metaparse/string.hpp>
  52
  53   #include <type_traits>
  54
  55   using namespace boost::metaparse;
  56
  57   debug_parsing_error<int_, BOOST_METAPARSE_STRING("not an int")> do_debugging;
  58
  59   int main() {}
  60
  61 By running the compiled executable you get the following:
  62
  63 Compile-time parsing results
  64 ----------------------------
  65 Input text:
  66 not an int
  67
  68 Parsing failed:
  69 line 1, col 1: Digit expected
  70
  71 [endsect]
  72