#ifndef __EXPR_H__
#define __EXPR_H__

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

typedef struct {
	size_t start, end;
	const char *err;
} ExprError;

typedef struct {
	const char *name;
	const char *description;
	double (*func)(double *args);
	const char **arg_names;
	size_t n_args;
} ExprBuiltinFunc;

typedef struct {
	const char *name;
	const char *description;
	double val;
} ExprBuiltinVar;

typedef struct _Expr Expr;

extern ExprBuiltinFunc *expr_builtin_funcs;
extern const size_t     expr_n_builtin_funcs;
extern ExprBuiltinVar  *expr_builtin_vars;
extern const size_t     expr_n_builtin_vars;

Expr *expr_new();
void expr_destroy(Expr *e);
ExprError expr_set(Expr *e, const char *expr) __attribute__((warn_unused_result));
ExprError expr_eval(Expr *e, double *out_res) __attribute__((warn_unused_result));
void expr_set_var(Expr *e, const char *name, double val);
bool expr_get_var(Expr *e, const char *name, double *out); /* Returns false if not present */
void expr_set_func(Expr *e, const char *name, double (*func)(double *args), size_t n_args);

#endif /* __EXPR_H__ */