text: // Copyright (C) 2018 T. Zachary Laine
  //
  // Distributed under the Boost Software License, Version 1.0. (See
  // accompanying file LICENSE_1_0.txt or copy at
  // http://www.boost.org/LICENSE_1_0.txt)
  #include <boost/parser/parser.hpp>
  
  #include <boost/mpl/assert.hpp>
  #include <boost/type_traits/is_same.hpp>
  
  #include <gtest/gtest.h>
  
  
  using namespace boost::parser;
  
  TEST(parser, symbols_empty)
  {
      symbols<int> roman_numerals;
      symbols<std::string> named_strings;
  
      std::string const str = "I";
      EXPECT_FALSE(parse(str, roman_numerals));
      EXPECT_FALSE(parse(str, named_strings));
  }
  
  TEST(parser, symbols_simple)
  {
      symbols<int> const roman_numerals = {
          {"I", 1}, {"V", 5}, {"X", 10}, {"L", 50}, {"C", 100}};
      symbols<std::string> const named_strings = {
          {"I", "1"}, {"V", "5"}, {"X", "10"}, {"L", "50"}, {"C", "100"}};
  
      {
          auto const result = parse("I", roman_numerals);
          EXPECT_TRUE(result);
          EXPECT_EQ(*result, 1);
      }
      {
          auto const result = parse("I", named_strings);
          EXPECT_TRUE(result);
          EXPECT_EQ(*result, "1");
      }
  
      {
          auto const result = parse("L", roman_numerals);
          EXPECT_TRUE(result);
          EXPECT_EQ(*result, 50);
      }
      {
          auto const result = parse("L", named_strings);
          EXPECT_TRUE(result);
          EXPECT_EQ(*result, "50");
      }
  }
  
  TEST(parser, symbols_mutating)
  {
      symbols<int> roman_numerals;
      roman_numerals.add("I", 1)("V", 5)("X", 10);
      auto const add_numeral = [&roman_numerals](auto & context) {
          using namespace boost::hana::literals;
          char chars[1] = {_attr(context)[0_c]};
          roman_numerals.insert(context, chars, _attr(context)[1_c]);
      };
      auto const numerals_parser = (char_ >> int_)[add_numeral] >> roman_numerals;
  
      {
          auto const result = parse("L50L", numerals_parser);
          EXPECT_TRUE(result);
          EXPECT_EQ(*result, 50);
          EXPECT_FALSE(parse("L", roman_numerals));
      }
      {
          auto const result = parse("C100C", numerals_parser);
          EXPECT_TRUE(result);
          EXPECT_EQ(*result, 100);
          EXPECT_FALSE(parse("C", roman_numerals));
      }
      {
          auto const result = parse("L50C", numerals_parser);
          EXPECT_FALSE(result);
      }
  }
  