▼ |  | Unstable: May Change Without Warning

1 | Guidelines for Developing unstable Libraries
2 | Automata: Compiling State Machines
3 | Bytes
4 | Contracts
5 | Converting Values to Strings
6 | Contracts for Macro Subexpressions
7 | Debugging
8 | Definitions
9 | Filesystem
10 | Find
11 | Flonums
12 | Futures
13 | Functions
14 | Hash Tables
15 | Interface-Oriented Programming for Classes
16 | Lazy Require
17 | Lists
18 | Logging
19 | Mark Parameters
20 | Match
21 | Parameter Groups
22 | Pretty-Printing
23 | Sequences
24 | Strings
25 | Structs
26 | Syntax
27 | Temporal Contracts: Explicit Contract Monitors
28 | GUI Libraries

On this page:

make
struct->list

Version: 5.3
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### 25`` Structs

Ryan Culpepper <ryanc@racket-lang.org>

This library is unstable; compatibility will not be maintained. See Unstable: May Change Without Warning for more information.

(require unstable/struct)

> > syntax

> > (make struct-id expr ...)

Creates an instance of struct-id, which must be bound as a struct name. The number of exprs is statically checked against the number of fields associated with struct-id. If they are different, or if the number of fields is not known, an error is raised at compile time.

Examples:

> > (define-struct triple (a b c))

> > (make triple 3 4 5)
> #<triple>
> > (make triple 2 4)
> eval:4:0: make: wrong number of arguments for struct triple
> (expected 3, got 2)
> in: (make triple 2 4)

> > procedure

> > (struct->list v [#:on-opaque on-opaque]) → (or/c list? #f)

> v : any/c
> on-opaque : (or/c 'error 'return-false 'skip) = 'error

Returns a list containing the struct instance v’s fields. Unlike struct->vector, 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:

> > (define-struct open (u v) #:transparent)

> > (struct->list (make-open 'a 'b))
> '(a b)
> > (struct->list #s(pre 1 2 3))
> '(1 2 3)
> > (define-struct (secret open) (x y))

> > (struct->list (make-secret 0 1 17 22))
> struct->list: expected argument of type <non-opaque struct>;
> given: (secret 0 1 ...)
> > (struct->list (make-secret 0 1 17 22) #:on-opaque 'return-false)
> #f
> > (struct->list (make-secret 0 1 17 22) #:on-opaque 'skip)
> '(0 1)
> > (struct->list 'not-a-struct #:on-opaque 'return-false)
> #f
> > (struct->list 'not-a-struct #:on-opaque 'skip)
> '()

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