23 Structures (BC)
A new Racket structure type is created with
scheme_make_struct_type. This creates the structure type, but
does not generate the constructor, etc. procedures. The
scheme_make_struct_values function takes a structure type and
creates these procedures. The scheme_make_struct_names function
generates the standard structure procedures names given the structure
type’s name. Instances of a structure type are created with
scheme_make_struct_instance and the function
scheme_is_struct_instance tests a structure’s type. The
scheme_struct_ref and scheme_struct_set functions access
or modify a field of a structure.
The structure procedure values and names generated by
scheme_make_struct_values and scheme_make_struct_names can
be restricted by passing any combination of these flags:
SCHEME_STRUCT_NO_TYPE — the structure type
value/name is not returned.
SCHEME_STRUCT_NO_CONSTR — the constructor procedure
value/name is not returned.
SCHEME_STRUCT_NO_PRED— the predicate procedure
value/name is not returned.
SCHEME_STRUCT_NO_GET — the selector procedure
values/names are not returned.
SCHEME_STRUCT_NO_SET — the mutator procedure
values/names are not returned.
SCHEME_STRUCT_GEN_GET — the field-independent
selector procedure value/name is returned.
SCHEME_STRUCT_GEN_SET — the field-independent
mutator procedure value/name is returned.
SCHEME_STRUCT_NO_MAKE_PREFIX — the constructor name
omits a make- prefix, like struct instead of
define-struct.
When all values or names are returned, they are returned as an array
with the following order: structure type, constructor, predicate,
first selector, first mutator, second selector, etc.,
field-independent select, field-independent mutator. When particular
values/names are omitted, the array is compressed accordingly.
Scheme_Object* | | scheme_make_struct_type | ( | Scheme_Object* base_name, | | | | | Scheme_Object* super_type, | | | | | Scheme_Object* inspector, | | | | | int num_init_fields, | | | | | int num_auto_fields, | | | | | Scheme_Object* auto_val, | | | | | Scheme_Object* properties, | | | | | Scheme_Object* guard) |
|
Creates and returns a new structure type. The base_name
argument is used as the name of the new structure type; it must be a
symbol. The super_type argument should be NULL or an
existing structure type to use as the super-type. The inspector
argument should be NULL or an inspector to manage the type.
The num_init_fields argument specifies the number of fields
for instances of this structure type that have corresponding
constructor arguments. (If a super-type is used, this is the number
of additional fields, rather than the total number.) The
num_auto_fields argument specifies the number of additional
fields that have no corresponding constructor arguments, and they are
initialized to auto_val. The properties argument is a
list of property-value pairs. The guard argument is either NULL
or a procedure to use as a constructor guard.
Scheme_Object** | scheme_make_struct_names | ( | Scheme_Object* base_name, | | | Scheme_Object* field_names, | | | int flags, | | | int* count_out) |
|
Creates and returns an array of standard structure value name
symbols. The
base_name argument is used as the name of the
structure type; it should be the same symbol passed to the associated
call to
scheme_make_struct_type. The
field_names argument
is a (Racket) list of field name symbols. The
flags argument
specifies which names should be generated, and if
count_out is
not
NULL,
count_out is filled with the number of names
returned in the array.
Creates and returns an array of the standard structure value and procedure values
for
struct_type. The
struct_type argument must be a structure type
value created by
scheme_make_struct_type. The
names procedure
must be an array of name symbols, generally the array returned by
scheme_make_struct_names. The
count argument specifies the
length of the
names array (and therefore the number of expected
return values) and the
flags argument specifies which values
should be generated.
Creates an instance of the structure type struct_type. The
argc and argv arguments provide the field values for the
new instance.
Returns 1 if v is an instance of struct_type or 0 otherwise.
Returns the nth field (counting from 0) in the structure s.
Sets the nth field (counting from 0) in the structure s to v.