63 lines
2.6 KiB
Racket
63 lines
2.6 KiB
Racket
#lang scribble/manual
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@(require scribble/eval "utils.rkt" (for-label racket unstable/parameter-group))
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@title{Parameter Groups}
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@unstable[@author+email["Neil Toronto" "ntoronto@racket-lang.org"]]
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@defmodule[unstable/parameter-group]
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Parameter groups are parameter-like @italic{views} that represent multiple parameters.
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@(define evaluator (make-base-eval))
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@examples[#:eval evaluator
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(require unstable/parameter-group)
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(define param1 (make-parameter 1))
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(define param2 (make-parameter 2))
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(define-parameter-group params (param1 param2))
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(params)
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(parameterize/group ([params (params-value 10 20)])
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(list (param1) (param2)))
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(params)
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(params (params-value 100 200))
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(list (param1) (param2))]
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Use parameter groups to conveniently set multiple parameters.
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For example, the @racketmodname[plot] library uses parameter groups to save and restore appearance-controlling parameters when it must draw plots within a thunk.
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@defproc[(parameter-group? [v any/c]) boolean?]{
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Returns @racket[#t] when @racket[v] is a parameter group.
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}
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@defform/subs[(define-parameter-group name (param-or-group-expr ...) options)
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([options code:blank
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(code:line #:struct struct-name)])
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#:contracts ([param-or-group-expr (or/c parameter? parameter-group?)])]{
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Defines a new parameter group.
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If @racket[struct-name] is not given, @racket[define-parameter-group] defines a new struct @racket[<name>-value] to hold the values of parameters.
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If @racket[struct-name] is given, it must have a constructor @racket[(struct-name param-or-group-expr ...)] that accepts as many arguments as there are parameters in the group, and a @racket[struct-name] match expander that accepts as many patterns as there are parameters.
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@examples[#:eval evaluator
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(struct two-params (p1 p2) #:transparent)
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(define-parameter-group params* (param1 param2) #:struct two-params)
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(params*)]
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}
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@defform[(parameterize/group ([param-or-group-expr value-expr] ...)
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body-expr ...+)
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#:contracts ([param-or-group-expr (or/c parameter? parameter-group?)])]{
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Corresponds to @racket[parameterize], but can parameterize parameter groups as well as parameters.
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}
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@defform[(parameterize*/group ([param-or-group-expr value-expr] ...)
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body-expr ...+)
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#:contracts ([param-or-group-expr (or/c parameter? parameter-group?)])]{
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Corresponds to @racket[parameterize*], but can parameterize parameter groups as well as parameters.
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}
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@close-eval[evaluator]
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