parse.hpp

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#ifndef PARSE_HPP_
#define PARSE_HPP_

#include <cstdlib>
#include <istream>
#include <locale>
#include <ostream>
#include <string>

#include "calc_error.hpp"
#include "node.hpp"

class parser
{
public:
  enum kind : int { eof, identifier, number,
    plus='+', minus='-', times='*', slash='/', lparen = '(', rparen=')', equal='=',
    comma=','};

  parser(std::istream& input);

  bool get_statement(std::ostream& output);

private:
  std::string charify(char c);
  bool get_number(std::string const& token, node& result);
  bool get_expr(node& result);
  bool get_add_expr(node& result);
  bool get_mul_expr(node& result);
  bool get_primary(node& result);
  bool get_unary(node& result);
  void get_definition(std::string& name, identifier_list& parameters, node& definition);
  kind get_token(std::string& token);
  void get_identifier(std::string& identifier);
  void get_expr_list(node_list& result);

  template<class OutputIterator>
  OutputIterator get_namelist(OutputIterator output);

  void push_back(std::string const& token, kind k);

  bool isalpha(char c) const { return ctype_.is(ctype_.alpha, c); }
  bool isalnum(char c) const { return ctype_.is(ctype_.alnum, c); }
  bool isdigit(char c) const { return ctype_.is(ctype_.digit, c); }
  bool isprint(char c) const { return ctype_.is(ctype_.print, c); }

  std::istream& input_;            
  std::ctype<char> const& ctype_;  
  std::string token_;              
  kind kind_;                      
};

void parse_loop(std::istream& input, std::ostream& output);

template<class OutputIterator>
OutputIterator parser::get_namelist(OutputIterator output)
{
  std::string token{};
  while (kind k = get_token(token)) {
    if (k == ')')
      return output;
    else if (k != identifier)
      throw syntax_error{"expected function parameter, got " + token};
    else {
      *output = token;
      ++output;

      k = get_token(token);
      if (k == ')')
        return output;
      if (k != ',')
        throw syntax_error{"expected comma in function paramter list, got " + token};
    }
  }
  throw syntax_error{"unexpected end of line in function parameter list"};
}


#endif