/* Expression tree stuff. */

#ifndef ETREE_H
#define ETREE_H

/*************************************************************************/

/* A node in an expression tree. */

typedef struct etree_struct ETree;

struct etree_struct {
    int type;			/* ET_* defines below */
    union {
	int intval;
	char *stringval;
	struct {
	    int func;		/* As returned by func_id() */
	    int nargs;
	    ETree **args;
	} funcval;
	struct {
	    ETree *arg1;
	    int operator;	/* OP_* defines below */
	    ETree *arg2;
	} exprval;
	struct {
	    ETree *expr;
	} subexprval;
    } u;
};

#define ET_INT		0
#define ET_STRING	1
#define ET_FUNC		2
#define ET_OPERATOR	3

/* This represents a parenthesized subexpression.  It serves no real
 * purpose other than to prevent order-of-operations from rearranging
 * arguments across parentheses. */
#define ET_SUBEXPR	255

/* Operator values.
 * Note that operator values are defined so that dividing by 10 gives a
 * precedence value with smaller values having greater precedence.
 */
#define OP_MULTIPLY	1000
#define OP_DIVIDE	1001
#define OP_MODULO	1002
#define OP_ADD		1010
#define OP_SUBTRACT	1011
#define OP_LSHIFT	1020
#define OP_RSHIFT	1021
#define OP_BNOT		1030
#define OP_BAND		1040
#define OP_BXOR		1050
#define OP_BOR		1060
#define OP_EQ		1070
#define OP_NE		1071
#define OP_LT		1072
#define OP_LE		1073
#define OP_GT		1074
#define OP_GE		1075
#define OP_LNOT		1080
#define OP_LAND		1090
#define OP_LOR		1100

/*************************************************************************/

/* Build an expression tree from the given input string.  Return in `tail'
 * the first character after the end of the valid expression string.  If
 * *tail == str, then no valid expression string could be found. */
extern ETree *etree_create(const char *str, char **tail);

/* Create an array of ETrees from a string containing a comma-separated
 * list of expressions.  This returns an array of ETree *'s, each one
 * representing one of the expressions.  The length of the array will be
 * returned via the `len' pointer.
 */
extern ETree **etree_create_list(const char *str, char **tail, int *len);

/* Free an expression tree. */
extern void etree_free(ETree *expr);

/* Free an array of expression trees. */
extern void etree_free_list(ETree **array, int size);

/* Evaluate an expression tree. */
extern ETree *etree_eval(ETree *expr);

/* Evaluate an expression tree as an integer. */
extern int etree_eval_i(ETree *expr);

/* Evaluate an expression tree as a string. */
extern char *etree_eval_s(ETree *expr);

/* Print the contents of an expression tree. */
extern void etree_print(ETree *expr);

/*************************************************************************/

#endif	/* ETREE_H */