3bb120545f
--- but Gwyth's amazingly helpful review of chapters 1-11
pointed out a few problems that are more difficult to fix
and are still pending
93 lines
3.7 KiB
Racket
93 lines
3.7 KiB
Racket
#lang scribble/doc
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@(require "mz.ss"
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(for-label racket/stxparam
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racket/stxparam-exptime
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racket/splicing))
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@title[#:tag "stxparam"]{Syntax Parameters}
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@note-lib-only[racket/stxparam]
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@defform[(define-syntax-parameter id expr)]{
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Binds @scheme[id] as syntax to a @deftech{syntax
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parameter}. The @scheme[expr] is an expression in the
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@tech{transformer environment} that serves as the default value for
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the @tech{syntax parameter}. The value is typically obtained by a transformer
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using @scheme[syntax-parameter-value].
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The @scheme[id] can be used with @scheme[syntax-parameterize]
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or @scheme[syntax-parameter-value] (in a transformer). If
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@scheme[expr] produces a procedure of one argument or a
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@scheme[make-set!-transformer] result, then @scheme[id] can be
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used as a macro. If @scheme[expr] produces a
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@scheme[rename-transformer] result, then @scheme[id] can be
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used as a macro that expands to a use of the target identifier, but
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@scheme[syntax-local-value] of @scheme[id] does not produce
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the target's value.}
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@defform[(syntax-parameterize ((id expr) ...) body-expr ...+)]{
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@margin-note/ref{See also @scheme[splicing-syntax-parameterize].}
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Each @scheme[id] must be bound to a @tech{syntax parameter} using
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@scheme[define-syntax-parameter]. Each @scheme[expr] is an expression
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in the @tech{transformer environment}. During the expansion of the
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@scheme[body-expr]s, the value of each @scheme[expr] is bound to the
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corresponding @scheme[id].
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If an @scheme[expr] produces a procedure of one argument or a
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@scheme[make-set!-transformer] result, then its @scheme[id]
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can be used as a macro during the expansion of the
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@scheme[body-expr]s. If @scheme[expr] produces a
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@scheme[rename-transformer] result, then @scheme[id] can be
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used as a macro that expands to a use of the target identifier, but
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@scheme[syntax-local-value] of @scheme[id] does not produce
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the target's value.}
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@; ----------------------------------------------------------------------
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@section{Syntax Parameter Inspection}
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@defmodule*/no-declare[(racket/stxparam-exptime)]
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@declare-exporting[racket/stxparam-exptime racket/stxparam]
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@defproc[(syntax-parameter-value [id-stx syntax?]) any]{
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This procedure is intended for use in a @tech{transformer
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environment}, where @scheme[id-stx] is an identifier bound in the
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normal environment to a @tech{syntax parameter}. The result is the current
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value of the @tech{syntax parameter}, as adjusted by
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@scheme[syntax-parameterize] form.
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This binding is provided @scheme[for-syntax] by
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@schememodname[racket/stxparam], since it is normally used in a
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transformer. It is provided normally by
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@schememodname[racket/stxparam-exptime].}
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@defproc[(make-parameter-rename-transformer [id-stx syntax?]) any]{
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This procedure is intended for use in a transformer, where
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@scheme[id-stx] is an identifier bound to a @tech{syntax parameter}. The
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result is a transformer that behaves as @scheme[id-stx], but that cannot
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be used with @scheme[syntax-parameterize] or
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@scheme[syntax-parameter-value].
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Using @scheme[make-parameter-rename-transformer] is analogous to
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defining a procedure that calls a parameter. Such a procedure can be
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exported to others to allow access to the parameter value, but not to
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change the parameter value. Similarly,
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@scheme[make-parameter-rename-transformer] allows a @tech{syntax parameter}
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to be used as a macro, but not changed.
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The result of @scheme[make-parameter-rename-transformer] is not
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treated specially by @scheme[syntax-local-value], unlike the result
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of @scheme[make-rename-transformer].
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This binding is provided @scheme[for-syntax] by
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@schememodname[racket/stxparam], since it is normally used in a
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transformer. It is provided normally by
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@schememodname[racket/stxparam-exptime].}
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