#include <stdio.h>
#include <stdlib.h>
#include <setjmp.h>

int nextc;
int match(int c)
{
  if (nextc == c) {
    do {
      nextc = getchar();
    } while (nextc == ' ');
    return 1;
  } else {
    return 0;
  }
}

jmp_buf env;
void error(viod)
{
  printf("syntax error.\n");
  while (nextc != '\n') {
    nextc = getchar();
  }
  longjmp(env, 1);
}

double exp0(void);
double exp1(double);
double term0(void);
double term1(double);
double factor(void);

int main()
{
  setjmp(env);
  nextc = getchar();
  printf("\nAnswer = %lf\n", exp0());
}

double exp0(void)
{                                   /* E -> TA */
  double v = term0();
  return exp1(v); 
}

double exp1(double v)
{
  if(match('+')) {                  /* A -> +TA */
    v += term0(); printf("+ "); return exp1(v);
  } else if(match('-')) {           /* A -> -TA */
    v -= term0(); printf("- "); return exp1(v);
  } else 
    return v;                       /* A -> epsilon */
}

double term0(void) {                /* T -> FB */
  double v = factor();
  return term1(v);
}

double term1(double v) {
  if(match('*')) {                  /* B -> *FB */
    v *= factor(); printf("* "); return term1(v);
  } else if(match('/')) {           /* B -> /FB */
    v /= factor(); printf("/ "); return term1(v);
  }  else                           /* B -> epsilon */
    return v;
}

#define N 1024
double factor(void) {               /* F -> 0...9 */

  static char buf[N];
  static char numtab[] = "0123456789.", *p;
  int flag, i;

  i = 0;
  while (1) {
    flag = 0;
    for (p = numtab; *p != '\0'; p++) {
      if (match(*p)) {
        flag = 1;
        break;
      }
    }
    if (flag == 1) {
      buf[i++] = (char)*p;
      continue;
    } else {
      if (i == 0)
        break;
      else
        buf[i] = '\0';
      printf("%s ", buf);
      return atof(buf);
    }
  }
  if(match('(')) {             /* F -> (E) */
    double v = exp0();
    if(match(')')) return v;
    else error();
  } else {
    error();
  }
}
/* end */

Timeout