#define ERR_DEEP_NESTING        1
#define ERR_PAREN_NOT_MATCH	2
#define ERR_NOT_A_NUMBER	3
#define ERR_NULL_FOUND		4
#define ERR_EXCESS_CHARACTERS	5
#define ERR_VAR_UNDEFINED	6

/* prototypes */
void setdegree(void);
void setradian(void);
int evaluate(char**, double*);