Expressions

Expressions — Query language expressions.

Synopsis

typedef             rasqal_expression;
enum                rasqal_op;
enum                rasqal_compare_flags;
enum                rasqal_pattern_flags;
rasqal_expression*  rasqal_new_0op_expression           (rasqal_op op);
rasqal_expression*  rasqal_new_1op_expression           (rasqal_op op,
                                                         rasqal_expression *arg);
rasqal_expression*  rasqal_new_2op_expression           (rasqal_op op,
                                                         rasqal_expression *arg1,
                                                         rasqal_expression *arg2);
rasqal_expression*  rasqal_new_3op_expression           (rasqal_op op,
                                                         rasqal_expression *arg1,
                                                         rasqal_expression *arg2,
                                                         rasqal_expression *arg3);
rasqal_expression*  rasqal_new_cast_expression          (raptor_uri *name,
                                                         rasqal_expression *value);
rasqal_expression*  rasqal_new_function_expression      (raptor_uri *name,
                                                         raptor_sequence *args);
rasqal_expression*  rasqal_new_literal_expression       (rasqal_literal *literal);
rasqal_expression*  rasqal_new_string_op_expression     (rasqal_op op,
                                                         rasqal_expression *arg1,
                                                         rasqal_literal *literal);
rasqal_expression*  rasqal_new_expression_from_expression
                                                        (rasqal_expression *e);
void                rasqal_free_expression              (rasqal_expression *e);
rasqal_literal*     rasqal_expression_evaluate          (rasqal_query *query,
                                                         rasqal_expression *e,
                                                         int flags);
void                rasqal_expression_print             (rasqal_expression *e,
                                                         FILE *fh);
void                rasqal_expression_print_op          (rasqal_expression *e,
                                                         FILE *fh);
int                 (*rasqal_expression_visit_fn)       (void *user_data,
                                                         rasqal_expression *e);
int                 rasqal_expression_visit             (rasqal_expression *e,
                                                         rasqal_expression_visit_fn fn,
                                                         void *user_data);

Description

Expressions form an expression tree that can be evaluated using rasqal_expression_evaluate() over rasqal_op operators, rasqal_literal constants and rasqal_variable values bound in some rasqal_query_result. The result is a rasqal_literal value.

Details

rasqal_expression

typedef struct rasqal_expression_s rasqal_expression;

expression (arg1), unary op (arg1), binary op (arg1,arg2), literal or variable

enum rasqal_op

typedef enum {
  /* internal */
  RASQAL_EXPR_UNKNOWN,
  RASQAL_EXPR_AND,
  RASQAL_EXPR_OR,
  RASQAL_EXPR_EQ,
  RASQAL_EXPR_NEQ,
  RASQAL_EXPR_LT,
  RASQAL_EXPR_GT,
  RASQAL_EXPR_LE,
  RASQAL_EXPR_GE,
  RASQAL_EXPR_UMINUS,
  RASQAL_EXPR_PLUS,
  RASQAL_EXPR_MINUS,
  RASQAL_EXPR_STAR,
  RASQAL_EXPR_SLASH,
  RASQAL_EXPR_REM,
  RASQAL_EXPR_STR_EQ,
  RASQAL_EXPR_STR_NEQ,
  RASQAL_EXPR_STR_MATCH,
  RASQAL_EXPR_STR_NMATCH,
  RASQAL_EXPR_TILDE,
  RASQAL_EXPR_BANG,
  RASQAL_EXPR_LITERAL,
  RASQAL_EXPR_FUNCTION,
  RASQAL_EXPR_BOUND,
  RASQAL_EXPR_STR,
  RASQAL_EXPR_LANG,
  RASQAL_EXPR_DATATYPE,
  RASQAL_EXPR_ISURI,
  RASQAL_EXPR_ISBLANK,
  RASQAL_EXPR_ISLITERAL,
  RASQAL_EXPR_CAST,
  RASQAL_EXPR_ORDER_COND_ASC,
  RASQAL_EXPR_ORDER_COND_DESC,
  RASQAL_EXPR_LANGMATCHES,
  RASQAL_EXPR_REGEX,
  RASQAL_EXPR_GROUP_COND_ASC,
  RASQAL_EXPR_GROUP_COND_DESC,
  RASQAL_EXPR_COUNT,
  RASQAL_EXPR_VARSTAR,
  RASQAL_EXPR_SAMETERM,
  /* internal */
  RASQAL_EXPR_LAST= RASQAL_EXPR_SAMETERM
} rasqal_op;

Rasqal expression operators. A mixture of unary, binary and tertiary operators (string matches). Also includes casting and two ordering operators from ORDER BY in SPARQL.

`RASQAL_EXPR_UNKNOWN`	Internal
`RASQAL_EXPR_AND`	Expression for AND(A, B)
`RASQAL_EXPR_OR`	Expression for OR(A, B)
`RASQAL_EXPR_EQ`	Expression for A equals B
`RASQAL_EXPR_NEQ`	Expression for A not equals B.
`RASQAL_EXPR_LT`	Expression for A less than B.
`RASQAL_EXPR_GT`	Expression for A greather than B.
`RASQAL_EXPR_LE`	Expression for A less than or equal to B.
`RASQAL_EXPR_GE`	Expression for A greater than or equal to B.
`RASQAL_EXPR_UMINUS`	Expression for -A.
`RASQAL_EXPR_PLUS`	Expression for +A.
`RASQAL_EXPR_MINUS`	Expression for A-B.
`RASQAL_EXPR_STAR`	Expression for A*B.
`RASQAL_EXPR_SLASH`	Expression for A/B.
`RASQAL_EXPR_REM`	Expression for A/B remainder.
`RASQAL_EXPR_STR_EQ`	Expression for A string equals B.
`RASQAL_EXPR_STR_NEQ`	Expression for A string not-equals B.
`RASQAL_EXPR_STR_MATCH`	Expression for string A matches literal regex B with flags.
`RASQAL_EXPR_STR_NMATCH`	Expression for string A not-matches literal regex B with flags.
`RASQAL_EXPR_TILDE`	Expression for binary not A.
`RASQAL_EXPR_BANG`	Expression for logical not A.
`RASQAL_EXPR_LITERAL`	Expression for a rasqal_literal.
`RASQAL_EXPR_FUNCTION`	Expression for a function A with arguments (B...).
`RASQAL_EXPR_BOUND`	Expression for SPARQL ISBOUND(A).
`RASQAL_EXPR_STR`	Expression for SPARQL STR(A).
`RASQAL_EXPR_LANG`	Expression for SPARQL LANG(A).
`RASQAL_EXPR_DATATYPE`	Expression for SPARQL DATATYPE(A).
`RASQAL_EXPR_ISURI`	Expression for SPARQL ISURI(A).
`RASQAL_EXPR_ISBLANK`	Expression for SPARQL ISBLANK(A).
`RASQAL_EXPR_ISLITERAL`	Expression for SPARQL ISLITERAL(A).
`RASQAL_EXPR_CAST`	Expression for cast literal A to type B.
`RASQAL_EXPR_ORDER_COND_ASC`	Expression for SPARQL order condition ascending.
`RASQAL_EXPR_ORDER_COND_DESC`	Expression for SPARQL order condition descending.
`RASQAL_EXPR_LANGMATCHES`	Expression for SPARQL LANGMATCHES(A, B).
`RASQAL_EXPR_REGEX`	Expression for string A matches expression regex B with flags.
`RASQAL_EXPR_GROUP_COND_ASC`	Expression for LAQRS group condition ascending.
`RASQAL_EXPR_GROUP_COND_DESC`	Expression for LAQRS group condition descending.
`RASQAL_EXPR_COUNT`	Expression for LAQRS select `COUNT()`
`RASQAL_EXPR_VARSTAR`	Expression for LAQRS select Variable *
`RASQAL_EXPR_SAMETERM`	Expression for SPARQL sameTerm
`RASQAL_EXPR_LAST`	Internal

enum rasqal_compare_flags

typedef enum {
  RASQAL_COMPARE_NOCASE = 1,
  RASQAL_COMPARE_XQUERY = 2,
  RASQAL_COMPARE_RDF    = 4,
  RASQAL_COMPARE_URI    = 8
} rasqal_compare_flags;

Flags for rasqal_expression_evaluate() or rasqal_literal_compare().

`RASQAL_COMPARE_NOCASE`	String comparisons are case independent.
`RASQAL_COMPARE_XQUERY`	XQuery comparsion rules apply.
`RASQAL_COMPARE_RDF`	RDF Term comparsion rules apply.
`RASQAL_COMPARE_URI`	Allow comparison of URIs

enum rasqal_pattern_flags

typedef enum {
  RASQAL_PATTERN_FLAGS_OPTIONAL=1,

  RASQAL_PATTERN_FLAGS_LAST=RASQAL_PATTERN_FLAGS_OPTIONAL
} rasqal_pattern_flags;

Flags for rasqal_graph_pattern.

`RASQAL_PATTERN_FLAGS_OPTIONAL`	True when the graph pattern is an optional match.
`RASQAL_PATTERN_FLAGS_LAST`	Internal

rasqal_new_0op_expression ()

rasqal_expression*  rasqal_new_0op_expression           (rasqal_op op);

Constructor - create a new 0-operand (constant) expression.

The operators are: RASQAL_EXPR_VARSTAR

The only operator here is the '*' in COUNT(*) as used by LAQRS.

`op` :	Expression operator
Returns :	a new rasqal_expression object or NULL on failure

rasqal_new_1op_expression ()

rasqal_expression*  rasqal_new_1op_expression           (rasqal_op op,
                                                         rasqal_expression *arg);

Constructor - create a new 1-operand expression. Takes ownership of the operand expression.

The operators are: RASQAL_EXPR_TILDE RASQAL_EXPR_BANG RASQAL_EXPR_UMINUS RASQAL_EXPR_BOUND RASQAL_EXPR_STR RASQAL_EXPR_LANG RASQAL_EXPR_LANGMATCHES RASQAL_EXPR_DATATYPE RASQAL_EXPR_ISURI RASQAL_EXPR_ISBLANK RASQAL_EXPR_ISLITERAL RASQAL_EXPR_ORDER_COND_ASC RASQAL_EXPR_ORDER_COND_DESC RASQAL_EXPR_GROUP_COND_ASC RASQAL_EXPR_GROUP_COND_DESC RASQAL_EXPR_COUNT

RASQAL_EXPR_BANG and RASQAL_EXPR_UMINUS are used by RDQL and SPARQL. RASQAL_EXPR_TILDE by RDQL only. The rest by SPARQL only.

`op` :	Expression operator
`arg` :	Operand 1
Returns :	a new rasqal_expression object or NULL on failure

rasqal_new_2op_expression ()

rasqal_expression*  rasqal_new_2op_expression           (rasqal_op op,
                                                         rasqal_expression *arg1,
                                                         rasqal_expression *arg2);

Constructor - create a new 2-operand expression. Takes ownership of the operand expressions.

The operators are: RASQAL_EXPR_AND RASQAL_EXPR_OR RASQAL_EXPR_EQ RASQAL_EXPR_NEQ RASQAL_EXPR_LT RASQAL_EXPR_GT RASQAL_EXPR_LE RASQAL_EXPR_GE RASQAL_EXPR_PLUS RASQAL_EXPR_MINUS RASQAL_EXPR_STAR RASQAL_EXPR_SLASH RASQAL_EXPR_REM RASQAL_EXPR_STR_EQ RASQAL_EXPR_STR_NEQ

RASQAL_EXPR_REM RASQAL_EXPR_STR_EQ and RASQAL_EXPR_STR_NEQ are not used by SPARQL. RASQAL_EXPR_REM is used by RDQL.

`op` :	Expression operator
`arg1` :	Operand 1
`arg2` :	Operand 2
Returns :	a new rasqal_expression object or NULL on failure

rasqal_new_3op_expression ()

rasqal_expression*  rasqal_new_3op_expression           (rasqal_op op,
                                                         rasqal_expression *arg1,
                                                         rasqal_expression *arg2,
                                                         rasqal_expression *arg3);

Constructor - create a new 3-operand expression. Takes ownership of the operands.

The only operator is: RASQAL_EXPR_REGEX

`op` :	Expression operator
`arg1` :	Operand 1
`arg2` :	Operand 2
`arg3` :	Operand 3 (may be NULL)
Returns :	a new rasqal_expression object or NULL on failure

rasqal_new_cast_expression ()

rasqal_expression*  rasqal_new_cast_expression          (raptor_uri *name,
                                                         rasqal_expression *value);

Constructor - create a new expression for casting and expression to a datatype. Takes ownership of the datatype uri and expression value.

`name` :	cast datatype URI
`value` :	expression value to cast to `datatype` type
Returns :	a new rasqal_expression object or NULL on failure

rasqal_new_function_expression ()

rasqal_expression*  rasqal_new_function_expression      (raptor_uri *name,
                                                         raptor_sequence *args);

Constructor - create a new expression for a function with expression arguments. Takes ownership of the function uri and arguments.

`name` :	function name
`args` :	sequence of rasqal_expression function arguments
Returns :	a new rasqal_expression object or NULL on failure

rasqal_new_literal_expression ()

rasqal_expression*  rasqal_new_literal_expression       (rasqal_literal *literal);

Constructor - create a new expression for a rasqal_literal Takes ownership of the operand literal.

`literal` :	Literal operand 1
Returns :	a new rasqal_expression object or NULL on failure

rasqal_new_string_op_expression ()

rasqal_expression*  rasqal_new_string_op_expression     (rasqal_op op,
                                                         rasqal_expression *arg1,
                                                         rasqal_literal *literal);

Constructor - create a new expression with one expression and one string operand. Takes ownership of the operands.

The operators are: RASQAL_EXPR_STR_MATCH (RDQL, SPARQL) and RASQAL_EXPR_STR_NMATCH (RDQL)

`op` :	Expression operator
`arg1` :	Operand 1
`literal` :	Literal operand 2
Returns :	a new rasqal_expression object or NULL on failure

rasqal_new_expression_from_expression ()

rasqal_expression*  rasqal_new_expression_from_expression
                                                        (rasqal_expression *e);

Copy Constructor - create a new rasqal_expression object from an existing rasqal_expression object.

`e` :	rasqal_expression object to copy
Returns :	a new rasqal_expression object or NULL on failure

rasqal_free_expression ()

void                rasqal_free_expression              (rasqal_expression *e);

Destructor - destroy a rasqal_expression object.

e :

rasqal_expression object

rasqal_expression_evaluate ()

rasqal_literal*     rasqal_expression_evaluate          (rasqal_query *query,
                                                         rasqal_expression *e,
                                                         int flags);

Evaluate a rasqal_expression tree to give a rasqal_literal result or error.

`query` :	rasqal_query this expression belongs to
`e` :	The expression to evaluate.
`flags` :	Flags for `rasqal_literal_compare()` and RASQAL_COMPARE_NOCASE for string matches.
Returns :	a rasqal_literal value or NULL on failure.

rasqal_expression_print ()

void                rasqal_expression_print             (rasqal_expression *e,
                                                         FILE *fh);

Print a Rasqal expression in a debug format.

The print debug format may change in any release.

`e` :	rasqal_expression object.
`fh` :	The FILE* handle to print to.

rasqal_expression_print_op ()

void                rasqal_expression_print_op          (rasqal_expression *e,
                                                         FILE *fh);

Print a rasqal expression operator in a debug format.

The print debug format may change in any release.

`e` :	the rasqal_expression object
`fh` :	the FILE* handle to print to

rasqal_expression_visit_fn ()

int                 (*rasqal_expression_visit_fn)       (void *user_data,
                                                         rasqal_expression *e);

User function to visit an expression and operate on it with rasqal_expression_visit()

`user_data` :	user data passed in with `rasqal_expression_visit()`
`e` :	current expression
Returns :	0 to truncate the visit

rasqal_expression_visit ()

int                 rasqal_expression_visit             (rasqal_expression *e,
                                                         rasqal_expression_visit_fn fn,
                                                         void *user_data);

Visit a user function over a rasqal_expression

If the user function fn returns 0, the visit is truncated.

`e` :	rasqal_expression to visit
`fn` :	visit function
`user_data` :	user data to pass to visit function
Returns :	0 if the visit was truncated.