/* arith.c: simple parser -- bold  evaluates */
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>  /* for pow */
char next;
double E(void);
double T(void);
double S(void);
double F(void);
void error(void);
void scan(void);
double evaluate(double arg1, char op, double arg2);

void main(void)
{
   double res;
   scan();
   res = E();
   if (next != '#') error();
   else 
      printf("Result is: %.16f\n", res);
}

double E(void)
{
   char save;
   double res, arg1, arg2;
   res = T();
   while (next == '+' || next == '-') {
      save = next;
      arg1 = res;
      scan();
      arg2 = T();
      res = evaluate(arg1, save, arg2);
   }
   return res;
}

double T(void)
{
   char save;
   double res, arg1, arg2;
   res = S();
   while (next == '*' || next == '/') {
      save = next;
      arg1 = res;
      scan();
      arg2 = S();
      res = evaluate(arg1, save, arg2);
   }
   return res;
}

double S(void)
{
   char save;
   double res, arg1, arg2;
   res = F();
   if (next == '^') {
      save = next;
      arg1 = res;
      scan();
      arg2 = S();
      res = evaluate(arg1, save, arg2);
   }
   return res;
}

double F(void)
{
   char save;
   double res;
   if (isdigit(next)) {
      save = next;
      scan();
      return (double)(save - '0');
   }
   else if (next == '(') {
      scan();
      res = E();
      if (next == ')') scan();
      else error();
      return res;
   }
   else {
      error();
      return 0;
   }
}
void scan(void)
{
   while (isspace(next = getchar()))
      ;
}
void error(void)
{
   printf("\n*** ERROR ***\n");
   exit(1);
}
double evaluate(double arg1, char op, double arg2)
{
   switch (op) {
   case '+': return arg1 + arg2;
   case '-': return arg1 - arg2;
   case '*': return arg1 * arg2;
   case '/': return arg1 / arg2;
   case '^': return pow(arg1, arg2);
   default: error(); return 0;
   }
}