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Docs for gen:custom-write.

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This commit is contained in:
Vincent St-Amour 2012-05-24 13:11:06 -04:00
parent 13b82e9a59
commit cee88f05dd
1 changed files with 21 additions and 16 deletions
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35
collects/scribblings/reference/custom-write.scrbl
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@ -3,15 +3,14 @@
@title{Printer Extension} @title{Printer Extension}
@defthing[prop:custom-write struct-type-property?]{ @defthing[gen:custom-write any/c]{
Associates a procedure to a structure type used by the default A @tech{generic interface} (see @secref["struct-generics"]) that
printer to @racket[display], @racket[write], or @racket[print] supplies a method, @racket[write-proc] used by the default printer to
instances of the structure type. @racket[display], @racket[write], or @racket[print] instances of the
structure type.
@moreref["structprops"]{structure type properties} A @racket[write-proc] method takes three
The procedure for a @racket[prop:custom-write] value takes three
arguments: the structure to be printed, the target port, and an arguments: the structure to be printed, the target port, and an
argument that is @racket[#t] for @racket[write] mode, @racket[#f] for argument that is @racket[#t] for @racket[write] mode, @racket[#f] for
@racket[display] mode, or @racket[0] or @racket[1] indicating @racket[display] mode, or @racket[0] or @racket[1] indicating
@ -51,7 +50,7 @@ so that graph and cycle structure can be represented.
@defexamples[ @defexamples[
(define (tuple-print tuple port mode) (define (tuple-print tuple port mode)
(when mode (write-string "<" port)) (when mode (write-string "<" port))
(let ([l (tuple-ref tuple 0)] (let ([l (tuple-ref tuple)]
[recur (case mode [recur (case mode
[(#t) write] [(#t) write]
[(#f) display] [(#f) display]
@ -64,20 +63,26 @@ so that graph and cycle structure can be represented.
(cdr (vector->list l))))) (cdr (vector->list l)))))
(when mode (write-string ">" port))) (when mode (write-string ">" port)))
(define-values (s:tuple make-tuple tuple? tuple-ref tuple-set!) (struct tuple (ref)
(make-struct-type 'tuple #f 1 0 #f #:methods gen:custom-write
(list (cons prop:custom-write tuple-print)))) [(define write-proc tuple-print)])
(display (make-tuple #(1 2 "a"))) (display (tuple #(1 2 "a")))
(print (make-tuple #(1 2 "a"))) (print (tuple #(1 2 "a")))
(let ([t (make-tuple (vector 1 2 "a"))]) (let ([t (tuple (vector 1 2 "a"))])
(vector-set! (tuple-ref t 0) 0 t) (vector-set! (tuple-ref t) 0 t)
(write t)) (write t))
] ]
} }
@defthing[prop:custom-write struct-type-property?]{
A deprecated @tech{structure type property} (see @secref["structprops"])
that supplies a procedure that corresponds to @racket[gen:custom-write]'s
@racket[write-proc]. @racket[gen:custom-write] should be used instead.
}
@defproc[(custom-write? [v any/c]) boolean?]{ @defproc[(custom-write? [v any/c]) boolean?]{
Returns @racket[#t] if @racket[v] has the @racket[prop:custom-write] Returns @racket[#t] if @racket[v] has the @racket[prop:custom-write]