#define EOL 0
#define NUM 1
#define PLUS_OP  2
#define MINUS_OP 3

extern int tokenVal;
extern int currentToken;

void getToken(void);

typedef struct _expr {    
    int kind;
    int val;
    struct _expr *left;
    struct _expr *right;
} Expr;

Expr *readExpr(void);
void printExpr(Expr *e);