#include <string>
#include "token.h"
#include "node.h"
#include "hashtable.h"
#include "lexan.h"
#include "world.h"

node * world::parse_highest()
{ token t = Lex.next();
  token_type tt = t.gettype();  
  if (tt == tnumber)
    return node::num(t.getvalue());
  else if (tt == tvariable)
    return node::var(t.getstring());
  else if (tt == toperator && t.getstring() == "(")
  { node * n = parse_expression();
    t = Lex.next();
    if (t.gettype() == toperator && t.getstring() == ")")
      return n;
    return node::err("error in parentheses"); }     
  return node::err("parse_highest"); }

node * world::parse_power()
{ node * L = parse_highest();
  token t = Lex.next();
  while (t.gettype() == toperator && t.getstring() == "^")
  { node * R = parse_highest();
    L = node::op("^", L, R);
    t = Lex.next(); }
  Lex.unnext(t);
  return L; }

node * world::parse_muldiv()
{ node * L = parse_power();
  token t = Lex.next();
  while (t.gettype() == toperator && (t.getstring() == "*" ||
                                      t.getstring() == "/"))
  { node * R = parse_power();
    L = node::op(t.getstring(), L, R);
    t = Lex.next(); }
  Lex.unnext(t);
  return L; }

node * world::parse_addsub()
{ node * L = parse_muldiv();
  token t = Lex.next();
  while (t.gettype() == toperator && (t.getstring() == "+" ||
                                      t.getstring() == "-"))
  { node * R = parse_muldiv();
    L = node::op(t.getstring(), L, R);
    t = Lex.next(); }
  Lex.unnext(t);
  return L; }

node * world::parse_expression()
{ return parse_addsub(); }