tokens.hpp

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#pragma once

#include <cstdlib>
#include <string>
#include <utility>

namespace reactions::tokens {

  template <char... C> struct token {
    static const size_t size = sizeof...(C);
  };

  using space = token<' '>;
  using arrow = token<'-', '>'>;
  using left_bra = token<'{'>;
  using right_bra = token<'}'>;

  template <char... C, std::size_t... I>
  bool match_token_impl(token<C...>, std::index_sequence<I...>,
                        std::string::const_iterator const &it) {
    return ((*(it + I) == C) && ...);
  }

  template <class Token>
  bool match_token(std::string::const_iterator const &it) {
    return match_token_impl(Token{}, std::make_index_sequence<Token::size>(),
                            it);
  }

  template <char... C> constexpr bool match_any(char c) {
    return ((C == c) || ...);
  }

  template <char C0, char C1> constexpr bool match_range(char c) {
    return (c >= C0) && (c <= C1);
  }
} // namespace reactions::tokens