/**
 * select OP NUM - Select values read from stdin for which VAL OP NUM
 *   holds.
 */

// +---------+--------------------------------------------------------
// | Headers |
// +---------+

#include <stdio.h>	// For scanf, printf
#include <ctype.h>	// For isdigit
#include <string.h>	// For strcmp
#include <stdlib.h>	// For atoi


// +-------+----------------------------------------------------------
// | Types |
// +-------+

enum operator { 
  LESS_THAN,     // <
  LESS_EQUAL,    // <=
  EQUALS,        // ==
  NOT_EQUAL,     // !=
  GREATER_EQUAL, // >=
  GREATER_THAN,  // >
  BITWISE_OR,    // |
  BITWISE_AND,   // &
  BITWISE_XOR    // ^
};


// +---------+--------------------------------------------------------
// | Helpers |
// +---------+

/**
 * looks_like_int(str) 
 *   Determine if the string looks like an integer.
 */
int
looks_like_int (char *str)
{
  int i = 0;

  // Skip over leading sign.
  if ((str[0] == '+') || (str[0] == '-'))
    ++i;

  // Consider remaining characters.
  while (str[i] != '\0')
    {
      if (! isdigit (str[i]))
        return 0;
      ++i;
    } // while

  // We've read through all the characters.  It must be an integer.
  return 1;
} // looks_like_int

/**
 * print_if_true (val, test)
 *   Prints val if test holds.
 */
void
print_if_true (int val, int test)
{
  if (test)
    printf ("%d\n", val);
} // print_if_true

/**
 * string_equal (str1, str2) 
 *   Determine if two strings are equal.
 */
int
string_equal (char str1[], char str2[])
{
  return (strcmp (str1, str2) == 0);
} // string_equal


// +------+-----------------------------------------------------------
// | Main |
// +------+

int
main (int argc, char *argv[])
{
  int val;      // The next number we've read
  int check;    // The result of scanf
  int num;	// The right-hand-side of the operator
  enum operator op;
		// The operator


  // Verify that we have the right number of parameters
  if (argc != 3)
    {
      printf ("Usage: %s OP NUM\n", argv[0]);
      return 1;
    }

  // Verify that the second paramter is a string that represents an
  // integer
  if (! looks_like_int (argv[2]))
    {
      printf ("Usage: %s OP NUM\n", argv[0]);
      printf ("  %s is not an integer.\n", argv[2]);
      return 2;
    }

  // Get the number parameter
  num = atoi (argv[2]);

  // Get the operator parameter 
  if (string_equal (argv[1], "<"))
    op = LESS_THAN;
  else if (string_equal (argv[1], "<="))
    op = LESS_EQUAL;
  else if (string_equal (argv[1], "=="))
    op = EQUALS;
  else if (string_equal (argv[1], "!="))
    op = NOT_EQUAL;
  else if (string_equal (argv[1], ">="))
    op = GREATER_EQUAL;
  else if (string_equal (argv[1], ">"))
    op = GREATER_THAN;
  else if (string_equal (argv[1], "|"))
    op = BITWISE_OR;
  else if (string_equal (argv[1], "&"))
    op = BITWISE_AND;
  else if (string_equal (argv[1], "^"))
    op = BITWISE_XOR;
  else
    {
      printf ("Invalid operator: %s\n", argv[1]);
      printf ("  Valid operators are <, <=, ==, !=, >, >=, |, &, and ^.\n");
      return 3;
    }

  // Process each input value
  while ((check = scanf ("%d", &val)) != EOF)
    {
      // Special case: Failed to read a number and failed to reach
      // end of file.
      if (check == 0)
        {
          printf ("Invalid input: '%c'\n", getchar ());
          continue;
        }
      // Normal case: Look at the operator and do the right thing
      switch (op)
        {
        case LESS_THAN:
          print_if_true (val, val < num);
	  break;
        case LESS_EQUAL:
          print_if_true (val, val <= num);
	  break;
        case EQUALS:
          print_if_true (val, val == num);
	  break;
        case NOT_EQUAL:
          print_if_true (val, val != num);
	  break;
        case GREATER_EQUAL:
          print_if_true (val, val >= num);
	  break;
        case GREATER_THAN:
          print_if_true (val, val > num);
	  break;
        case BITWISE_OR:
          print_if_true (val, val | num);
	  break;
        case BITWISE_AND:
          print_if_true (val, val & num);
	  break;
        case BITWISE_XOR:
          print_if_true (val, val ^ num);
	  break;
        } // switch
    } // while

  // And we're done
  return 0;
} // main