#ifndef __PBG_H__
#define __PBG_H__
/*********************************************************
* *
* Prefix Boolean Grammar (PBG), a lightweight C library *
* By Tyler J. Daddio, November 2018 *
* *
*********************************************************/
/* Used to suppress compiler warnings for intentionally unused arguments. This
* isn't as foolproof as GCC's unused attribute, but it is not compiler-
* dependent, which is just dandy. */
#define PBG_UNUSED(x) (void)(x)
/* Used to represent the result of an expression evaluation. */
#define PBG_FALSE 0
#define PBG_TRUE 1
#define PBG_ERROR -1
/*****************************
* *
* EXPRESSION REPRESENTATION *
* *
*****************************/
/**
* Types of PBG fields.
*/
typedef enum {
PBG_NULL, /* NULL: Unknown field type */
/* Type literals. */
PBG_MIN_LT_TP,
PBG_LT_TP_DATE, /* DATE TYPE literal */
PBG_LT_TP_BOOL, /* TRUE/FALSE TYPE literal */
PBG_LT_TP_NUMBER, /* NUMBER TYPE literal */
PBG_LT_TP_STRING, /* STRING TYPE literal */
/* Add more TYPE literals here. */
PBG_MAX_LT_TP,
/* Literals. */
PBG_MIN_LT,
PBG_LT_TRUE, /* TRUE literal */
PBG_LT_FALSE, /* FALSE literal */
PBG_LT_NUMBER, /* NUMBER literal */
PBG_LT_STRING, /* STRING literal */
PBG_LT_DATE, /* DATE literal */
PBG_LT_VAR, /* VARiable literal */
/* Add more literals here. */
PBG_MAX_LT,
/* Operators. */
PBG_MIN_OP,
PBG_OP_NOT, /* ! NOT */
PBG_OP_AND, /* & AND */
PBG_OP_OR, /* | OR */
PBG_OP_EQ, /* = EQUAL */
PBG_OP_LT, /* < LESS THAN */
PBG_OP_GT, /* > GREATER THAN */
PBG_OP_EXST, /* ? EXISTS */
PBG_OP_NEQ, /* != NOT EQUAL */
PBG_OP_LTE, /* <= LESS THAN OR EQUAL TO */
PBG_OP_GTE, /* >= GREATER THAN OR EQUAL TO */
PBG_OP_TYPE, /* @ TYPE OF */
/* Add more operators here. */
PBG_MAX_OP
} pbg_field_type;
/**
* This struct represents a PBG field. A field can be either a literal or an
* operator. This is determined by its type. For operators, the data pointer
* describes a list of pointers to other fields in the abstract syntax tree.
* For constants, it describes data relevant to the field type.
*/
typedef struct {
pbg_field_type _type; /* Node type, determines the type/size of data. */
int _int; /* Type determines what this is used for! */
void* _data; /* Arbitrary data! */
} pbg_field;
/**
* This struct represents a PBG expression. There are two arrays in this
* representation: one for constants, and one for variables. Both types are
* represented by fields.
*/
typedef struct {
pbg_field* _constants; /* Constants. */
pbg_field* _variables; /* Variables. */
int _numconst; /* Number of constants. */
int _numvars; /* Number of variables. */
} pbg_expr;
/************************
* *
* ERROR REPRESENTATION *
* *
************************/
/**
* Type specifiers for all possible PBG errors.
*/
typedef enum {
PBG_ERR_NONE,
PBG_ERR_ALLOC,
PBG_ERR_STATE,
PBG_ERR_SYNTAX,
PBG_ERR_UNKNOWN_TYPE,
PBG_ERR_OP_ARITY,
PBG_ERR_OP_ARG_TYPE
} pbg_error_type;
/**
* Represents a PBG error. Errors may be generated during parsing and
* evaluation and should be checked by the caller.
*/
typedef struct {
pbg_error_type _type; /* Error type. */
int _line; /* Line of file where error occurred. */
char* _file; /* File in which error occurred. */
int _int; /* Type determines what this is used for! */
void* _data; /* Data to be included with error report. */
} pbg_error;
/***************
* *
* EXPRESSIONS *
* *
***************/
/**
* Parses the string as a boolean expression in Prefix Boolean Grammar.
* @param e PBG expression instance to initialize.
* @param err Container to store error, if any occurs.
* @param str String to parse. This must be terminated with '\0'.
*/
void pbg_parse(pbg_expr* e, pbg_error* err, char* str);
/**
* Parses the string as a boolean expression in Prefix Boolean Grammar.
* @param e PBG expression instance to initialize.
* @param err Container to store error, if any occurs.
* @param str String to parse.
* @param n Length of the string.
*/
void pbg_parse_n(pbg_expr* e, pbg_error* err, char* str, int n);
/**
* Evaluates the PBG expression with the provided assignments.
* @param e PBG expression to evaluate.
* @param err Container to store error, if any occurs.
* @param dict Dictionary used to resolve VAR names.
* @return 1 if the PBG expression evaluates to true with the given dictionary.
* 0 otherwise.
*/
int pbg_evaluate(pbg_expr* e, pbg_error* err, pbg_field (*dict)(char*, int));
/**
* Destroys the PBG expression instance and frees all associated resources.
* This function does not free the provided pointer.
* @param e PBG expression to destroy.
*/
void pbg_free(pbg_expr* e);
/**************
* *
* FIELDS *
* *
**************/
/**
* Makes a field representing a DATE.
* @param year Year of the date.
* @param month Month of the date.
* @param day Day of the date.
* @return a new DATE field.
*/
pbg_field pbg_make_date(int year, int month, int day);
/**
* Makes a field representing a BOOL.
* @param truth Truth value of the new BOOL.
* @return a new BOOL field.
*/
pbg_field pbg_make_bool(int truth);
/**
* Makes a field representing a NUMBER.
* @param value Numeric value of the NUMBER.
* @return a new NUMBER field.
*/
pbg_field pbg_make_number(double value);
/**
* Makes a field representing a STRING.
* @param value Value of the STRING.
* @return a new STRING field.
*/
pbg_field pbg_make_string(char* str);
/**
* Makes a field representing NULL.
* @return a new NULL field.
*/
pbg_field pbg_make_null(void);
/***************
* *
* ERRORS *
* *
***************/
/**
* Checks if the given error has been initialized with error data.
* @param err Error to check.
* @return 1 if the given error has been initialized, 0 otherwise.
*/
int pbg_iserror(pbg_error* err);
/**
* Prints a human-readable representation of the given pbg_error to the
* standard output.
* @param err Error to print.
*/
void pbg_error_print(pbg_error* err);
/**
* Frees resources being used by the given error, if any. This function does
* not free the provided pointer.
* @param e PBG error to clean up.
*/
void pbg_error_free(pbg_error* e);
#endif /* __PBG_H__ */
