#ifndef _token_h
#define _token_h

/* Kinds of symbols encountered while parsing an arithmetic expression */

enum symbol {NUMBER, PLUS, MINUS, TIMES, DIVIDE, L_PAREN, R_PAREN, 
  EOL, UNDEF} ;


/* Data structure for a token */

typedef struct {
   enum symbol kind ; 
   int value ;
} token_t ;

/* Data structure for input string */

#define BUFLEN 256

typedef struct {
   char str[BUFLEN] ;   /* input string */
   int pos ;            /* current position */
   int last ;           /* last position */
   int looked ;		/* = 1, if looked ahead. = 0, otherwise */
   int lookahead_pos ;  /* stopped scanning here, after looking */
   token_t lookahead ;
} input_t ;


/* Support functions */

input_t *ReadInput(void) ;
void EatToken(input_t *) ;
token_t LookAhead(input_t *) ;
void PrintError(input_t *) ;

#endif