lexer.hpp

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#pragma once
 
#include <string>
 
#include "stax/utils/result.hpp"
#include "tokens.hpp"
 
namespace stax::lexer {
 
#undef EOF
 
DEFINE_ERROR("lexer", Error, EOF, Syntax, IllegalCharacter)
 
const std::unordered_map<std::string_view, token::Type> kKeywords = {
    {"let", token::Type::kLet},
    {"fn", token::Type::kFn},
};
 
class Lexer {
 public:
  Lexer(std::string input);
 
  auto NextToken() -> result_t<token::Token>;
 
 private:
  static auto IsWhitespace(const char c) {
    constexpr std::array kWhitespaceChars{' ', '\t', '\n'};
    return std::ranges::any_of(kWhitespaceChars, [c](const char whitespace) {
      return c == whitespace;
    });
  }
 
  static auto IsLetter(const char c) {
    return std::isalpha(c) || c == '_';
  }
 
  static auto IsDigit(const char c) {
    return std::isdigit(c) || c == '.';
  }
 
  auto NextChar() -> result_t<char>;
 
  void Advance();
 
  auto Identifier() -> result_t<std::string_view>;
  auto Number() -> result_t<std::string_view>;
  void ConsumeWhitespace();
 
  std::string input_;
  bool started = false;
  std::string::iterator curr_;
  std::string::iterator peek_;
};
 
}  // namespace stax::lexer