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Holyrel Library Reference Manual | ![]() |
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RestrictRestrict — Restrict. |
#include <libhrel/relation.h> HRelationRestrict; gboolean (*HTuplePredFunc) (HTuple *tuple, gpointer user_data); HRelation* h_relation_restrict (HRelation *relation, HTuplePredFunc predicate_func, gpointer user_data); HRelation* h_relation_restrict_attrs (HRelation *relation, ...);
typedef struct _HRelationRestrict HRelationRestrict;
A HRelation representing a restricted relation.
gboolean (*HTuplePredFunc) (HTuple *tuple, gpointer user_data);
A HTuple predicate function.
tuple : |
a HTuple |
user_data : |
user data |
Returns : | either TRUE or FALSE |
HRelation* h_relation_restrict (HRelation *relation, HTuplePredFunc predicate_func, gpointer user_data);
Restricts relation
to the set of tuples evaluating to TRUE with
predicate_func
.
HRelation* h_relation_restrict_attrs (HRelation *relation, ...);
Restricts relation
to the set of tuples which contain the
attribute values listed.
relation : |
relation to restrict |
... : |
name and value of an attribute, followed by another and so
on, then a NULL .
|
Returns : | restricted relation |
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