suzanne.soy/racket
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Docs for gen:custom-write.

Browse Source
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
collects/scribblings/reference/custom-write.scrbl
View File

@ -3,15 +3,14 @@
@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
printer to @racket[display], @racket[write], or @racket[print]
instances of the structure type.
A @tech{generic interface} (see @secref["struct-generics"]) that
supplies a method, @racket[write-proc] used by the default printer to
@racket[display], @racket[write], or @racket[print] instances of the
structure type.
@moreref["structprops"]{structure type properties}
The procedure for a @racket[prop:custom-write] value takes three
A @racket[write-proc] method takes three
arguments: the structure to be printed, the target port, and an
argument that is @racket[#t] for @racket[write] mode, @racket[#f] for
@racket[display] mode, or @racket[0] or @racket[1] indicating
@ -20,7 +19,7 @@ procedure should print the value to the given port using
@racket[write], @racket[display], @racket[print], @racket[fprintf],
@racket[write-special], etc.
The @tech{port write handler}, @tech{port display handler},
The @tech{port write handler}, @tech{port display handler},
and @tech{print handler} are specially
configured for a port given to a custom-write procedure. Printing to
the port through @racket[display], @racket[write], or @racket[print]
@ -51,7 +50,7 @@ so that graph and cycle structure can be represented.
@defexamples[
(define (tuple-print tuple port mode)
(when mode (write-string "<" port))
(let ([l (tuple-ref tuple 0)]
(let ([l (tuple-ref tuple)]
[recur (case mode
[(#t) write]
[(#f) display]
@ -64,20 +63,26 @@ so that graph and cycle structure can be represented.
(cdr (vector->list l)))))
(when mode (write-string ">" port)))
(define-values (s:tuple make-tuple tuple? tuple-ref tuple-set!)
(make-struct-type 'tuple #f 1 0 #f
(list (cons prop:custom-write tuple-print))))
(struct tuple (ref)
#:methods gen:custom-write
[(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"))])
(vector-set! (tuple-ref t 0) 0 t)
(let ([t (tuple (vector 1 2 "a"))])
(vector-set! (tuple-ref t) 0 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?]{
Returns @racket[#t] if @racket[v] has the @racket[prop:custom-write]