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Add an example for #:defaults.

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Vincent St-Amour 2013-09-03 11:30:32 -04:00
parent 4453a4318c
commit c9a0761a0d
1 changed files with 13 additions and 6 deletions
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19
pkgs/racket-pkgs/racket-doc/scribblings/reference/generic.scrbl
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@ -2,10 +2,6 @@
@(require (for-label racket/base racket/generic)) @(require (for-label racket/base racket/generic))
@title[#:tag "struct-generics"]{Generic Interfaces} @title[#:tag "struct-generics"]{Generic Interfaces}
@; @author[@author+email["Eli Barzilay" "eli@racket-lang.org"]
@; @author+email["Jay McCarthy" "jay@racket-lang.org"]
@; @author+email["Vincent St-Amour" "stamourv@racket-lang.org"]
@; @author+email["Asumu Takikawa" "asumu@racket-lang.org"]]
@defmodule[racket/generic] @defmodule[racket/generic]
@ -21,8 +17,8 @@ a structure type are defined using the @racket[#:methods] keyword
[method-id . kw-formals*] ... [method-id . kw-formals*] ...
generics-opt ...) generics-opt ...)
([generics-opt ([generics-opt
(code:line #:fast-defaults ([fast-pred? fast-impl ...] ...))
(code:line #:defaults ([default-pred? default-impl ...] ...)) (code:line #:defaults ([default-pred? default-impl ...] ...))
(code:line #:fast-defaults ([fast-pred? fast-impl ...] ...))
(code:line #:fallbacks [fallback-impl ...]) (code:line #:fallbacks [fallback-impl ...])
(code:line #:defined-predicate defined-pred-id) (code:line #:defined-predicate defined-pred-id)
(code:line #:defined-table defined-table-id) (code:line #:defined-table defined-table-id)
@ -177,7 +173,16 @@ syntax error.}
(define-generics printable (define-generics printable
(gen-print printable [port]) (gen-print printable [port])
(gen-port-print port printable) (gen-port-print port printable)
(gen-print* printable [port] #:width width #:height [height])) (gen-print* printable [port] #:width width #:height [height])
#:defaults ([string?
(define/generic super-print gen-print)
(define (gen-print s [port (current-output-port)])
(fprintf port "String: ~a" s))
(define (gen-port-print port s)
(super-print s port))
(define (gen-print* s [port (current-output-port)]
#:width w #:height [h 0])
(fprintf port "String (~ax~a): ~a" w h s))]))
(define-struct num (v) (define-struct num (v)
#:methods gen:printable #:methods gen:printable
@ -208,6 +213,8 @@ syntax error.}
(gen-port-print (current-output-port) x) (gen-port-print (current-output-port) x)
(gen-print* x #:width 100 #:height 90) (gen-print* x #:width 100 #:height 90)
(gen-print "Strings are printable too!")
(define y (make-bool #t)) (define y (make-bool #t))
(gen-print y) (gen-print y)
(gen-port-print (current-output-port) y) (gen-port-print (current-output-port) y)