parser/test/parser.cpp

/**
 *   Copyright (C) 2018 Zach 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 <gtest/gtest.h>


using namespace boost::parser;


TEST(parser, basic)
{
    constexpr auto parser_1 = char_ >> char_;
    constexpr auto parser_2 = char_ >> char_ >> char_;
    constexpr auto parser_3 = char_ | char_;
    constexpr auto parser_4 = char_('a') | char_('b') | char_('c');
    constexpr auto parser_5 = char_('a') | char_('b') | eps;

    {
        std::string str = "a";
        EXPECT_TRUE(parse(str, char_));
        EXPECT_TRUE(!parse(str, char_('b')));
    }
    {
        std::string str = "a";
        char c = '\0';
        EXPECT_TRUE(parse(str, char_, c));
        EXPECT_EQ(c, 'a');
        EXPECT_TRUE(!parse(str, char_('b')));
    }
    {
        std::string str = "b";
        char c = '\0';
        EXPECT_TRUE(parse(str, char_("ab"), c));
        EXPECT_EQ(c, 'b');
        EXPECT_TRUE(!parse(str, char_("cd")));
    }
    {
        std::string str = "b";
        char c = '\0';
        std::string const pattern_1 = "ab";
        std::string const pattern_2 = "cd";
        EXPECT_TRUE(parse(str, char_(pattern_1), c));
        EXPECT_EQ(c, 'b');
        EXPECT_TRUE(!parse(str, char_(pattern_2)));
    }
    {
        std::string str = "b";
        char c = '\0';
        EXPECT_TRUE(parse(str, char_('a', 'b'), c));
        EXPECT_EQ(c, 'b');
        EXPECT_TRUE(!parse(str, char_('c', 'd')));
    }
    {
        std::string str = " ";
        char c = '\0';
        EXPECT_TRUE(parse(str, ascii::blank, c));
        EXPECT_EQ(c, ' ');
        EXPECT_TRUE(!parse(str, ascii::lower));
    }
    {
        std::string str = "ab";
        EXPECT_TRUE(parse(str, char_));
        EXPECT_TRUE(parse(str, parser_1));
        EXPECT_TRUE(!parse(str, parser_2));
    }
    {
        std::string str = "ab";
        std::vector<char> result;
        EXPECT_TRUE(parse(str, parser_1, result));
        using namespace boost::hana::literals;
        EXPECT_EQ(result[0_c], 'a');
        EXPECT_EQ(result[1_c], 'b');
    }
    {
        std::string str = "abc";
        EXPECT_TRUE(parse(str, parser_1));
        EXPECT_TRUE(parse(str, parser_2));
    }
    {
        std::string str = "abc";
        std::vector<char> result;
        EXPECT_TRUE(parse(str, parser_2, result));
        using namespace boost::hana::literals;
        EXPECT_EQ(result[0_c], 'a');
        EXPECT_EQ(result[1_c], 'b');
        EXPECT_EQ(result[2_c], 'c');
    }
    {
        std::string str = "a";
        EXPECT_TRUE(parse(str, parser_3));
        EXPECT_TRUE(parse(str, parser_4));
    }
    {
        std::string str = "a";
        char c = '\0';
        EXPECT_TRUE(parse(str, parser_3, c));
        EXPECT_EQ(c, 'a');
    }
    {
        std::string str = "a";
        char c = '\0';
        EXPECT_TRUE(parse(str, parser_4, c));
        EXPECT_EQ(c, 'a');
    }
    {
        std::string str = "z";
        EXPECT_TRUE(parse(str, parser_3));
        EXPECT_TRUE(!parse(str, parser_4));
    }
    {
        std::string str = "a";
        EXPECT_TRUE(parse(str, parser_5));
    }
    {
        std::string str = "z";
        EXPECT_TRUE(parse(str, parser_5));
    }
    {
        std::string str = "a";
        boost::optional<char> c;
        EXPECT_TRUE(parse(str, parser_5, c));
        EXPECT_EQ(c, 'a');
    }
    {
        std::string str = "z";
        boost::optional<char> c;
        EXPECT_TRUE(parse(str, parser_5, c));
        EXPECT_EQ(c, boost::none);
    }
}

TEST(parser, int_uint)
{
    {
        std::string str = "-42";
        int i = 0;
        EXPECT_TRUE(parse(str, int_, i));
        EXPECT_EQ(i, -42);
    }
    {
        std::string str = "42";
        int i = 0;
        EXPECT_TRUE(parse(str, int_, i));
        EXPECT_EQ(i, 42);
    }
    {
        std::string str = "-42";
        int i = 3;
        EXPECT_TRUE(!parse(str, uint_, i));
        EXPECT_EQ(i, 3);
    }
    {
        std::string str = "42";
        int i = 0;
        EXPECT_TRUE(parse(str, uint_, i));
        EXPECT_EQ(i, 42);
    }
}

TEST(parser, star)
{
    {
        constexpr auto parser = *char_;
        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "a";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'a'}));
        }
        {
            std::string str = "ba";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'b', 'a'}));
        }
    }

    {
        constexpr auto parser = *char_('b');
        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "b";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'b'}));
        }
        {
            std::string str = "bb";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'b', 'b'}));
        }
    }
}

TEST(parser, plus)
{
    {
        constexpr auto parser = +char_;

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(!parse(str, parser, chars));
        }
        {
            std::string str = "a";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'a'}));
        }
        {
            std::string str = "ba";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'b', 'a'}));
        }
    }

    {
        constexpr auto parser = +char_('b');

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(!parse(str, parser, chars));
        }
        {
            std::string str = "b";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'b'}));
        }
        {
            std::string str = "bb";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'b', 'b'}));
        }
    }
}

TEST(parser, star_and_plus_collapsing)
{
    {
        constexpr auto parser = +(+char_('b'));

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(!parse(str, parser, chars));
        }
        {
            std::string str = "b";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'b'}));
        }
        {
            std::string str = "bb";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'b', 'b'}));
        }
    }

    {
        constexpr auto parser = **char_('z');

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "z";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z'}));
        }
        {
            std::string str = "zz";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z', 'z'}));
        }
    }

    {
        constexpr auto parser = +*char_('z');

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "z";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z'}));
        }
        {
            std::string str = "zz";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z', 'z'}));
        }
    }

    {
        constexpr auto parser = *+char_('z');

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "z";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z'}));
        }
        {
            std::string str = "zz";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z', 'z'}));
        }
    }
}

TEST(parser, action)
{
    {
#if 0 // Must not compile, because the action makes the parser return a nope!
        {
            auto action = [&ss](auto & context) { ss << _attr(context); };
            auto parser = *char_('b')[action];
            std::vector<char> chars;
            EXPECT_TRUE(!parse(str, parser, chars));
        }
#endif

        {
            std::string str = "";
            std::stringstream ss;
            auto action = [&ss](auto & context) { ss << _attr(context); };
            auto parser = *char_('b')[action];
            EXPECT_TRUE(parse(str, parser));
            EXPECT_EQ(ss.str(), "");
        }
        {
            std::string str = "b";
            std::stringstream ss;
            auto action = [&ss](auto & context) { ss << _attr(context); };
            auto parser = *char_('b')[action];
            EXPECT_TRUE(parse(str, parser));
            EXPECT_EQ(ss.str(), "b");
        }
        {
            std::string str = "bb";
            std::stringstream ss;
            auto action = [&ss](auto & context) { ss << _attr(context); };
            auto parser = *char_('b')[action];
            EXPECT_TRUE(parse(str, parser));
            EXPECT_TRUE(parse(str, parser));
            EXPECT_EQ(ss.str(), "bbbb");
        }
    }

    {
#if 0 // Must not compile, because the action makes the parser return a nope!
        {
            auto action = [&ss](auto & context) { ss << _attr(context); };
            auto parser = +char_('b')[action];
            std::vector<char> chars;
            EXPECT_TRUE(!parse(str, parser, chars));
        }
#endif

        {
            std::string str = "";
            std::stringstream ss;
            auto action = [&ss](auto & context) { ss << _attr(context); };
            auto parser = +char_('b')[action];
            EXPECT_TRUE(!parse(str, parser));
            EXPECT_EQ(ss.str(), "");
        }
        {
            std::string str = "b";
            std::stringstream ss;
            auto action = [&ss](auto & context) { ss << _attr(context); };
            auto parser = +char_('b')[action];
            EXPECT_TRUE(parse(str, parser));
            EXPECT_EQ(ss.str(), "b");
        }
        {
            std::string str = "bb";
            std::stringstream ss;
            auto action = [&ss](auto & context) { ss << _attr(context); };
            auto parser = +char_('b')[action];
            EXPECT_TRUE(parse(str, parser));
            EXPECT_TRUE(parse(str, parser));
            EXPECT_EQ(ss.str(), "bbbb");
        }
    }
}

TEST(parser, star_as_string_or_vector)
{
    {
        constexpr auto parser = *char_('z');

        {
            std::string str = "";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "");
        }
        {
            std::string str = "z";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "z");
        }
        {
            std::string str = "zz";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "zz");
        }
    }

    {
        constexpr auto parser = *char_('z');

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "z";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z'}));
        }
        {
            std::string str = "zz";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z', 'z'}));
        }
    }

    {
        constexpr auto parser = *string("zs");

        {
            std::string str = "";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "");
            }
        }
        {
            std::string str = "z";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "");
            }
        }
        {
            std::string str = "zs";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "zs");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "zs");
            }
        }
        {
            std::string str = "zszs";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "zszs");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "zszs");
            }
        }
    }

    {
        constexpr auto parser = *string("zs");

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "z";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
        }
        {
            std::string str = "zs";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z', 's'}));
        }
        {
            std::string str = "zszs";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>({'z', 's', 'z', 's'}));
        }
    }
}

TEST(parser, omit)
{
    {
        constexpr auto parser = omit[*+char_('z')];

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "z";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "zz";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser));
        }
        {
            std::string str = "z";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser));
        }
        {
            std::string str = "zz";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser));
        }
    }

    {
        constexpr auto parser = omit[*string("zs")];

        {
            std::string str = "";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "z";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
        }
        {
            std::string str = "zs";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
        {
            std::string str = "zszs";
            std::vector<char> chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, std::vector<char>());
        }
    }
}

TEST(parser, repeat)
{
    {
        constexpr auto parser = repeat(2, 3)[string("zs")];

        {
            std::string str = "";
            std::string chars;
            EXPECT_TRUE(!parse(str, parser, chars));
            EXPECT_EQ(chars, "");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(!chars);
            }
        }
        {
            std::string str = "z";
            std::string chars;
            EXPECT_TRUE(!parse(str, parser, chars));
            EXPECT_EQ(chars, "");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(!chars);
            }
        }
        {
            std::string str = "zs";
            std::string chars;
            EXPECT_TRUE(!parse(str, parser, chars));
            EXPECT_EQ(chars, "");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(!chars);
            }
        }
        {
            std::string str = "zszs";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "zszs");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "zszs");
            }
        }
    }
}

TEST(parser, raw)
{
    {
        constexpr auto parser = raw[*string("zs")];
        using range_t = range<std::string_view::const_iterator>;

        {
            std::string str = "";
            range_t r;
            EXPECT_TRUE(parse(str, parser, r));
            EXPECT_EQ(r, range_t(&*str.begin(), &*str.begin()));
        }
        {
            std::string str = "z";
            range_t r;
            EXPECT_TRUE(parse(str, parser, r));
            EXPECT_EQ(r, range_t(&*str.begin(), &*str.begin()));
        }
        {
            std::string str = "zs";
            range_t r;
            EXPECT_TRUE(parse(str, parser, r));
            EXPECT_EQ(r, range_t(&*str.begin(), &*str.end()));
        }
        {
            std::string str = "zszs";
            range_t r;
            EXPECT_TRUE(parse(str, parser, r));
            EXPECT_EQ(r, range_t(&*str.begin(), &*str.end()));
        }
        {
            std::string str = "";
            boost::optional<range_t> result = parse(str, parser);
            EXPECT_TRUE(result);
            EXPECT_EQ(*result, range_t(&*str.begin(), &*str.begin()));
        }
        {
            std::string str = "z";
            boost::optional<range_t> result = parse(str, parser);
            EXPECT_TRUE(result);
            EXPECT_EQ(*result, range_t(&*str.begin(), &*str.begin()));
        }
        {
            std::string str = "zs";
            boost::optional<range_t> result = parse(str, parser);
            EXPECT_TRUE(result);
            EXPECT_EQ(*result, range_t(&*str.begin(), &*str.end()));
        }
        {
            std::string str = "zszs";
            boost::optional<range_t> result = parse(str, parser);
            EXPECT_TRUE(result);
            EXPECT_EQ(*result, range_t(&*str.begin(), &*str.end()));
        }
    }
}

TEST(parser, delimited)
{
    {
        constexpr auto parser = string("yay") % ',';

        {
            std::string str = "";
            std::string chars;
            EXPECT_TRUE(!parse(str, parser, chars));
            EXPECT_EQ(chars, "");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(!chars);
            }
        }
        {
            std::string str = "z";
            std::string chars;
            EXPECT_TRUE(!parse(str, parser, chars));
            EXPECT_EQ(chars, "");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(!chars);
            }
        }
        {
            std::string str = ",";
            std::string chars;
            EXPECT_TRUE(!parse(str, parser, chars));
            EXPECT_EQ(chars, "");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(!chars);
            }
        }
        {
            std::string str = ",yay";
            std::string chars;
            EXPECT_TRUE(!parse(str, parser, chars));
            EXPECT_EQ(chars, "");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(!chars);
            }
        }
        {
            std::string str = "yay";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "yay");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "yay");
            }
        }
        {
            std::string str = "yayyay";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "yay");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "yay");
            }
        }
        {
            std::string str = "yay,";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "yay");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "yay");
            }
        }
        {
            std::string str = "yay,yay,yay";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "yayyayyay");

            {
                boost::optional<std::string> const chars = parse(str, parser);
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "yayyayyay");
            }
        }
    }

    {
        constexpr auto parser = string("yay") % ',';
        {
            std::string str = "";
            std::string chars;
            EXPECT_TRUE(!skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "");
        }

        {
            std::string str = "";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(!chars);
        }
        {
            std::string str = "z";
            std::string chars;
            EXPECT_TRUE(!skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "");
        }
        {
            std::string str = "z";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(!chars);
        }
        {
            std::string str = ",";
            std::string chars;
            EXPECT_TRUE(!skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "");
        }
        {
            std::string str = ",";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(!chars);
        }
        {
            std::string str = " ,yay";
            std::string chars;
            EXPECT_TRUE(!skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "");
        }
        {
            std::string str = " ,yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(!chars);
        }
        {
            std::string str = ", yay";
            std::string chars;
            EXPECT_TRUE(!skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "");
        }
        {
            std::string str = ", yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(!chars);
        }
        {
            std::string str = ",yay ";
            std::string chars;
            EXPECT_TRUE(!skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "");
        }
        {
            std::string str = ",yay ";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(!chars);
        }

        {
            std::string str = " , yay ";
            std::string chars;
            EXPECT_TRUE(!skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "");
        }
        {
            std::string str = " , yay ";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(!chars);
        }
        {
            std::string str = "yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yay");
        }
        {
            std::string str = "yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yay");
        }
        {
            std::string str = "yayyay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yay");
        }
        {
            std::string str = "yayyay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yay");
        }
        {
            std::string str = "yay,";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yay");
        }
        {
            std::string str = "yay,";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yay");
        }
        {
            std::string str = "yay,yay,yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");
        }
        {
            std::string str = "yay,yay,yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
        {
            std::string str = " yay,yay,yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");
        }
        {
            std::string str = " yay,yay,yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
        {
            std::string str = "yay ,yay,yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");
        }

        {
            std::string str = "yay ,yay,yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
        {
            std::string str = "yay, yay,yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");
        }
        {
            std::string str = "yay, yay,yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
        {
            std::string str = "yay,yay ,yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");
        }

        {
            std::string str = "yay,yay ,yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
        {
            std::string str = "yay,yay, yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");
        }

        {
            std::string str = "yay,yay, yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
        {
            std::string str = "yay,yay,yay ";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");
        }

        {
            std::string str = "yay,yay,yay ";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
        {
            std::string str = " yay , yay , yay ";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");
        }

        {
            std::string str = " yay , yay , yay ";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
        {
            std::string str = "yay, yay, yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");
        }

        {
            std::string str = "yay, yay, yay";
            boost::optional<std::string> const chars =
                skip_parse(str, parser, char_(' '));
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
    }
}

TEST(parser, lexeme)
{
    {
        constexpr auto parser = lexeme[string("yay") % ','];

        {
            std::string str = "yay, yay, yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yay");

            {
                std::string str = "yay, yay, yay";
                boost::optional<std::string> const chars =
                    skip_parse(str, parser, char_(' '));
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "yay");
            }
        }
        {
            std::string str = " yay, yay, yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yay");

            {
                std::string str = " yay, yay, yay";
                boost::optional<std::string> const chars =
                    skip_parse(str, parser, char_(' '));
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "yay");
            }
        }
    }

    {
        constexpr auto parser = lexeme[skip[string("yay") % ',']];

        {
            std::string str = "yay, yay, yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");

            {
                std::string str = "yay, yay, yay";
                boost::optional<std::string> const chars =
                    skip_parse(str, parser, char_(' '));
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "yayyayyay");
            }
        }
        {
            std::string str = " yay, yay, yay";
            std::string chars;
            EXPECT_TRUE(skip_parse(str, parser, char_(' '), chars));
            EXPECT_EQ(chars, "yayyayyay");

            {
                std::string str = " yay, yay, yay";
                boost::optional<std::string> const chars =
                    skip_parse(str, parser, char_(' '));
                EXPECT_TRUE(chars);
                EXPECT_EQ(*chars, "yayyayyay");
            }
        }
    }
}

TEST(parser, skip)
{
    {
        constexpr auto parser = skip(char_(' '))[string("yay") % ','];

        {
            std::string str = "yay, yay, yay";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "yayyayyay");
        }
        {
            std::string str = "yay, yay, yay";
            boost::optional<std::string> const chars = parse(str, parser);
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
        {
            std::string str = " yay, yay, yay";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "yayyayyay");
        }
        {
            std::string str = " yay, yay, yay";
            boost::optional<std::string> const chars = parse(str, parser);
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "yayyayyay");
        }
    }
}

TEST(parser, combined_seq_and_or)
{
    {
        constexpr auto parser = char_('a') >> char_('b') >> char_('c') |
                                char_('x') >> char_('y') >> char_('z');
        {
            std::string str = "abc";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "abc");
        }

        {
            std::string str = "abc";
            boost::optional<std::vector<char>> const chars = parse(str, parser);
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, std::vector<char>({'a', 'b', 'c'}));
        }

        {
            std::string str = "xyz";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "xyz");
        }
    }

    {
        constexpr auto parser = char_('a') >> string("b") >> char_('c') |
                                char_('x') >> string("y") >> char_('z');
        {
            std::string str = "abc";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "abc");
        }

        {
            std::string str = "abc";
            boost::optional<std::string> const chars = parse(str, parser);
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "abc");
        }

        {
            std::string str = "xyz";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "xyz");
        }
    }

    {
        constexpr auto parser = char_('a') >> char_('b') >> char_('c') |
                                char_('x') >> char_('y') >> char_('z');
        {
            std::string str = "abc";
            boost::any chars;
            EXPECT_TRUE(parse(str, parser, chars));
        }

        {
            std::string str = "xyz";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "xyz");
        }
    }

    {
        constexpr auto parser = string("a") >> string("b") >> string("c") |
                                string("x") >> string("y") >> string("z");
#if 0 // Expected to fail.
        {
            std::string str = "abc";
            boost::any chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(boost::any_cast<std::string>(chars), "abc");
        }
#endif

        {
            std::string str = "xyz";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "xyz");
        }
    }

    {
        constexpr auto parser = !char_('a');
        std::string str = "a";
        EXPECT_TRUE(!parse(str, parser));
    }

    {
        constexpr auto parser = &char_('a');
        std::string str = "a";
        EXPECT_TRUE(parse(str, parser));
    }

    {
        constexpr auto parser = char_('a') >> string("b") > char_('c') |
                                char_('x') >> string("y") >> char_('z');
        {
            std::string str = "abc";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "abc");
        }

        {
            std::string str = "abc";
            boost::optional<std::string> const chars = parse(str, parser);
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "abc");
        }

        {
            std::string str = "xyz";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "xyz");
        }

        {
            std::string str = "abz";
            std::string chars;
            EXPECT_ANY_THROW(
                parse(str, parser, rethrow_error_handler{}, chars));
        }

        {
            std::string str = "abz";
            std::string chars;
            EXPECT_TRUE(!parse(str, parser, chars));
        }

        {
            std::string str = "abz";
            std::string chars;
            EXPECT_TRUE(!parse(
                str,
                parser,
                default_error_handler("simple_parser.cpp"),
                chars));
        }

        {
            std::string str = "ab";
            std::string chars;
            EXPECT_TRUE(!parse(
                str,
                parser,
                default_error_handler("simple_parser.cpp"),
                chars));
        }
    }

    {
        constexpr auto parser = char_('a') >> string("b") > char_('c') |
                                char_('x') >> string("y") >> char_('z');
        {
            std::string str = "abc";
            std::string chars;
            EXPECT_TRUE(parse(str, parser, chars));
            EXPECT_EQ(chars, "abc");
        }

        {
            std::string str = "abc";
            boost::optional<std::string> const chars = parse(str, parser);
            EXPECT_TRUE(chars);
            EXPECT_EQ(*chars, "abc");
        }

        {
            std::string str = "xyz";
            std::string chars;
            EXPECT_TRUE(debug_parse(str, parser, chars));
            EXPECT_EQ(chars, "xyz");
        }
    }
}

#if 0
TEST(parser, TODO)
{
    {
        constexpr auto parser =
            *(char_('a') >> string("b") > lit('c') >> lit("str") |
              char_('x') >> string("y") >> char_('z'));
        std::string str = "xyz";
        std::string chars;
        EXPECT_TRUE(debug_parse(str, parser, chars));
    }
    {
        constexpr auto parser = +char_('x');
        std::string str = "xyz";
        std::string chars;
        EXPECT_TRUE(debug_parse(str, parser, chars));
    }
    {
        constexpr auto parser = *char_('x');
        std::string str = "xyz";
        std::string chars;
        EXPECT_TRUE(debug_parse(str, parser, chars));
    }
    {
        constexpr auto parser = repeat(3, 4)[char_('h')];
        std::string str = "hhh";
        debug_parse(str, parser);
    }
    {
        constexpr auto parser = char_ % ',';
        std::string str = "h,i,j";
        debug_parse(str, parser);
    }
}
#endif