#include "lexer.h"
#include <iostream>


using namespace std;

double apply(char op, double x, double y);

int main(void) {
  char buf[1024];
  double numbers[1024];
  char operators[1024];
  int ntop=0;  //top of the number stack
  int otop=0;  //top of the operator stack
  int depth = 0;  //depth of parenthen
  double y, x;
  
  //read a line
  cin.getline(buf, 1024);

  //lex the line
  LexicalElement le = nextElement(buf);

  do {
    switch(le.type) {
    case LPAREN:
      depth++;
      break;
    case RPAREN:
      depth--;
      //pop 2 operands
      y = numbers[--ntop];
      x = numbers[--ntop];

      //push the result of applying the top operator
      numbers[ntop++] = apply(operators[--otop], x, y);
      break;
    case OPERATOR:
      //push the operator onto the operator stack
      operators[otop++] = le.value.c;
      break;
    case NUMBER:
      //push onto the number stack
      numbers[ntop++] = le.value.num;
      break;
    }

    //get the next element
    le = nextElement(0x00);
  } while(le.type != ERROR && le.type != EOS);

  //check for errors
  if(le.type==ERROR) {
    cerr << "Syntax Error" << endl;
  } else if(depth != 0) {
    cerr << "Mismatched Parenthesis" << endl;
  } else {
    cout << "Result: " << numbers[--ntop] << endl;
  }
  
  return 0;
}


double apply(char op, double x, double y) {
  switch(op) {
  case '+':
    return x+y;
    break;
  case '-':
    return x-y;
    break;
  case '*':
    return x*y;
    break;
  case '/':
    return x/y;
    break;
  }

  //unreachable
  return 0;
}