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Showing content from http://docs.racket-lang.org/reference/structutils.html below:

5.6 Structure Utilities

Creates a vector representing

. The first slot of the result vector contains a symbol whose printed name has the form

. Each remaining slot contains either the value of a field in

, if it is accessible via the current inspector, or

for a field that is not accessible. A single

value is used in the vector for contiguous inaccessible fields. (Consequently, the size of the vector does not match the size of the

if more than one field is inaccessible.)

Returns

if

exposes any structure types of

with the current inspector,

otherwise.

Typically, when (struct? v) is true, then (struct->vector v) exposes at least one field value. It is possible, however, for the only visible types of v to contribute zero fields.

Returns #t if v is a structure type descriptor value, #f otherwise.

Returns

if

is not an instance of a

structure type. Otherwise, the result is the shorted key that could be used with

to create an instance of the structure type.

Examples:

> (prefab-struct-key #s(cat "Garfield"))

'cat

> (struct cat (name) #:prefab) > (struct cute-cat cat (shipping-dest) #:prefab) > (cute-cat "Nermel" "Abu Dhabi")

'#s((cute-cat cat 1) "Nermel" "Abu Dhabi")

> (prefab-struct-key (cute-cat "Nermel" "Abu Dhabi"))

'(cute-cat cat 1)

Creates an instance of a

structure type, using the

s as field values. The

and the number of

s determine the

structure type.

A key identifies a structure type based on a list with the following items:

• A symbol for the structure type’s name.

• An exact, nonnegative integer representing the number of non-automatic fields in the structure type, not counting fields from the supertype (if any).

• A list of two items, where the first is an exact, nonnegative integer for the number of automatic fields in the structure type that are not from the supertype (if any), and the second element is an arbitrary value that is the value for the automatic fields.

• A vector of exact, nonnegative integers that indicate mutable non-automatic fields in the structure type, counting from 0 and not including fields from the supertype (if any).

• Nothing else, if the structure type has no supertype. Otherwise, the rest of the list is the key for the supertype.

An empty vector and an auto-field list that starts with 0 can be omitted. Furthermore, the first integer (which indicates the number of non-automatic fields) can be omitted, since it can be inferred from the number of supplied vs. Finally, a single symbol can be used instead of a list that contains only a symbol (in the case that the structure type has no supertype, no automatic fields, and no mutable fields).

The total field count must be no more than 32768. If the number of fields indicated by key is inconsistent with the number of supplied vs, the exn:fail:contract exception is raised.

Examples:

Added in version 8.5.0.8 of package base.

If the number of fields indicated by key is inconsistent with field-count, the exn:fail:contract exception is raised.

Return

if

can be a

structure type key,

otherwise.

See make-prefab-struct for a description of valid key shapes.

Produces a function suitable as a value for

or

. The function prints values in “constructor style.” When the value is

ed as an expression, it is shown as an application of the constructor (as returned by

) to the contents (as returned by

). When given to

, it is shown as an unreadable value with the constructor separated from the contents by a colon.

Examples:

> (print (point 1 2))

(point 1 2)

> (write (point 1 2))

#<point: 1 2>

The function also cooperates with pretty-print:

#<point:

 3000000

 4000000>

Note that the printer uses a separate property,

, to determine whether a struct instance is quotable. If so, the printer may print it in

mode it in certain contexts, such as within a list. For example:

> (print (list (point 1 2) (point 3 4)))

'(#<point: 1 2> #<point: 3 4>)

> (print (list (point2 1 2) (point2 3 4)))

(list (point 1 2) (point 3 4))

Keyword arguments can be simulated with unquoted-printing-string:

; Private implementation ; Public ``constructor'' > (define (kwpoint #:x x #:y y)     (kwpoint-impl x y)) ; Example use > (print (kwpoint #:x 1 #:y 2))

(kwpoint #:x 1 #:y 2)

> (write (kwpoint #:x 3 #:y 4))

#<kwpoint: #:x 3 #:y 4>

Added in version 6.3 of package base.

Returns a list containing the struct instance

’s fields. Unlike

, the struct name itself is not included.

If any fields of v are inaccessible via the current inspector the behavior of struct->list is determined by on-opaque. If on-opaque is 'error (the default), an error is raised. If it is 'return-false, struct->list returns #f. If it is 'skip, the inaccessible fields are omitted from the list.

Examples:

Added in version 6.3 of package base.

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