A record type is a first class object representing a user-defined data type. A record is an instance of a record type.
Note that in many ways, this interface is too low-level for every-day use. Most uses of records are better served by SRFI-9 records. See SRFI-9 Records.
#t if obj is a record of any type and
record? may be true of any Scheme value; there is no
promise that records are disjoint with other Scheme types.
Create and return a new record-type descriptor.
type-name is a string naming the type. Currently it’s only used
in the printed representation of records, and in diagnostics.
field-names is a list of elements of the form
(mutable name), or name, where
name are symbols naming the fields of a record of the type.
Duplicates are not allowed among these symbols, unless
allow-duplicate-field-names? is true.
(make-record-type "employee" '(name age salary))
The optional print argument is a function used by
write, etc, for printing a record of the new
type. It’s called as
(print record port) and should look
at record and write to port.
#:parent keyword to derive a record type from a
supertype. A derived record type has the fields from its parent type,
followed by fields declared in the
make-record-type call. Record
predicates and field accessors for instance of a parent type will also
work on any instance of a subtype.
Allowing record subtyping has a small amount of overhead. To avoid this
overhead, prevent extensibility by passing
By default, record types in Guile are not extensible.
Generally speaking, calling
make-record-type returns a fresh
record type; it generates new record types. However sometimes
you only want to define a record type if one hasn’t been defined
already. For a nongenerative record type definition, pass a
symbol as the
#:uid keyword parameter. If a record with the
given uid was already defined, it will be returned instead. The
type name, fields, parent (if any), and so on for the previously-defined
type must be compatible.
R6RS defines a notion of “opaque” record types. Given an instance of
an opaque record type, one cannot obtain a run-time representation of
the record type. See rnrs records procedural, for full details. The
#:opaque? flag is used by Guile’s R6RS layer to record this
information. The default is determined by whether the parent type, if
any, was opaque.
Fields are mutable by default, meaning that
return a procedure that can update a record in place. Specifying a
field using the form
(immutable name) instead marks a field
Return a procedure for constructing new members of the type represented by rtd. The result will be a procedure accepting exactly as many arguments as there are fields in the record type.
Return a procedure for testing membership in the type represented by rtd. The returned procedure accepts exactly one argument and returns a true value if the argument is a member of the indicated record type; it returns a false value otherwise.
Return a procedure for reading the value of a particular field of a member of the type represented by rtd. The returned procedure accepts exactly one argument which must be a record of the appropriate type; it returns the current value of the field named by the symbol field-name in that record.
If field-name is a symbol, it must be a member of the list of
field-names in the call to
make-record-type that created the type
represented by rtd. If multiple fields in rtd have the same
record-accessor returns the first one.
If field-name is an integer, it should be an index into
(record-type-fields rtd). This allows accessing fields
with duplicate names.
Return a procedure for writing the value of a particular field of a
member of the type represented by rtd. The returned procedure
accepts exactly two arguments: first, a record of the appropriate type,
and second, an arbitrary Scheme value; it modifies the field named by
the symbol field-name in that record to contain the given value.
The returned value of the modifier procedure is unspecified. The symbol
field-name is a field name or a field index, as in
Return a record-type descriptor representing the type of the given
record. That is, for example, if the returned descriptor were passed to
record-predicate, the resulting predicate would return a true
value when passed the given record. Note that it is not necessarily the
case that the returned descriptor is the one that was passed to
record-constructor in the call that created the constructor
procedure that created the given record.
Return the type-name associated with the type represented by rtd. The
returned value is
eqv? to the type-name argument given in
the call to
make-record-type that created the type represented by
Return a list of the symbols naming the fields in members of the type
represented by rtd. The returned value is
equal? to the
field-names argument given in the call to
created the type represented by rtd.