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
251 lines
11 KiB
Racket
251 lines
11 KiB
Racket
#lang scribble/doc
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@(require "mz.ss")
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@title[#:tag "stxops"]{Syntax Object Content}
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@defproc[(syntax? [v any/c]) boolean?]{
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Returns @scheme[#t] if @scheme[v] is a @tech{syntax object}, @scheme[#f]
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otherwise. See also @secref["stxobj-model"].}
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@defproc[(syntax-source [stx syntax?]) any]{
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Returns the source for the @tech{syntax object} @scheme[stx], or @scheme[#f]
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if none is known. The source is represented by an arbitrary value
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(e.g., one passed to @scheme[read-syntax]), but it is typically a file
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path string. Source-location information is dropped for a syntax
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object that is marshaled as part of compiled code; see also
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@scheme[current-compile].}
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@defproc[(syntax-line [stx syntax?])
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(or/c exact-positive-integer? #f)]{
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Returns the line number (positive exact integer) for the start of the
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@tech{syntax object} in its source, or @scheme[#f] if the line number or
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source is unknown. The result is @scheme[#f] if and only if
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@scheme[(syntax-column stx)] produces @scheme[#f]. See also
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@secref["linecol"], and see @scheme[syntax-source] for information
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about marshaling compiled @tech{syntax object}s.}
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@defproc[(syntax-column [stx syntax?])
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(or/c exact-nonnegative-integer? #f)]{
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Returns the column number (non-negative exact integer) for the start
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of the @tech{syntax object} in its source, or @scheme[#f] if the source
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column is unknown. The result is @scheme[#f] if and only if
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@scheme[(syntax-line stx)] produces @scheme[#f]. See also
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@secref["linecol"], and see @scheme[syntax-source] for information
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about marshaling compiled @tech{syntax object}s.}
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@defproc[(syntax-position [stx syntax?])
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(or/c exact-positive-integer? #f)]{
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Returns the character position (positive exact integer) for the start
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of the @tech{syntax object} in its source, or @scheme[#f] if the source
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position is unknown. See also @secref["linecol"], and see
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@scheme[syntax-source] for information about marshaling compiled
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@tech{syntax object}s.}
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@defproc[(syntax-span [stx syntax?])
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(or/c exact-nonnegative-integer? #f)]{
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Returns the span (non-negative exact integer) in characters of the
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@tech{syntax object} in its source, or @scheme[#f] if the span is
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unknown. See also @scheme[syntax-source] for information about
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marshaling compiled @tech{syntax object}s.}
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@defproc[(syntax-original? [stx syntax?]) boolean?]{
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Returns @scheme[#t] if @scheme[stx] has the property that
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@scheme[read-syntax] and @scheme[read-honu-syntax] attach to the
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@tech{syntax object}s that they generate (see @secref["stxprops"]), and if
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@scheme[stx]'s @tech{lexical information} does not indicate that the
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object was introduced by a syntax transformer (see
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@secref["stxobj-model"]). The result is @scheme[#f] otherwise. This
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predicate can be used to distinguish @tech{syntax object}s in an expanded
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expression that were directly present in the original expression, as
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opposed to @tech{syntax object}s inserted by macros.}
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@defproc[(syntax-source-module [stx syntax?] [source? any/c #f])
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(or/c module-path-index? symbol? path? #f)]{
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Returns an indication of the module whose source contains
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@scheme[stx], or @scheme[#f] if @scheme[stx] has no source module. If
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@scheme[source?] is @scheme[#f], then result is a module path index or
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symbol (see @secref["modpathidx"]); if @scheme[source?] is true, the
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result is a path or symbol corresponding to the loaded module's
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source in the sense of @scheme[current-module-declare-source].}
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@defproc[(syntax-e [stx syntax?]) any]{
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Unwraps the immediate datum structure from a @tech{syntax object},
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leaving nested syntax structure (if any) in place. The result of
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@scheme[(syntax-e stx)] is one of the following:
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@itemize[
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@item{a symbol}
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@item{a @tech{syntax pair} (described below)}
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@item{the empty list}
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@item{an immutable vector containing @tech{syntax object}s}
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@item{an immutable box containing @tech{syntax object}s}
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@item{an immutable @tech{hash table} containing @tech{syntax
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object} values (but not necessarily @tech{syntax object} keys)}
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@item{an immutable @tech{prefab} structure containing @tech{syntax object}s}
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@item{some other kind of datum---usually a number, boolean, or string}
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]
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A @deftech{syntax pair} is a pair containing a @tech{syntax object} as its
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first element, and either the empty list, a syntax pair, or a syntax
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object as its second element.
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A @tech{syntax object} that is the result of @scheme[read-syntax] reflects
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the use of delimited @litchar{.} in the input by creating a syntax
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object for every pair of parentheses in the source, and by creating a
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pair-valued @tech{syntax object} @italic{only} for parentheses in the
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source. See @secref["parse-pair"] for more information.}
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@defproc[(syntax->list [stx syntax?]) (or/c list? #f)]{
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Returns a list of @tech{syntax object}s or @scheme[#f]. The result is a list
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of @tech{syntax object}s when @scheme[(syntax->datum stx)] would produce a
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list. In other words, @tech{syntax pairs} in @scheme[(syntax-e stx)]
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are flattened.}
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@defproc[(syntax->datum [stx syntax?]) any]{
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Returns a datum by stripping the lexical information, source-location
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information, properties, and certificates from @scheme[stx]. Inside of
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pairs, (immutable) vectors, (immutable) boxes, immutable @tech{hash
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table} values (not keys), and immutable @tech{prefab} structures,
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@tech{syntax object}s are recursively stripped.
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The stripping operation does not mutate @scheme[stx]; it creates new
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pairs, vectors, boxes, hash tables, and @tech{prefab} structures as
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needed to strip lexical and source-location information recursively.}
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@defproc[(datum->syntax [ctxt (or/c syntax? #f)]
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[v any/c]
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[srcloc (or/c syntax? #f
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(list/c any/c
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(or/c exact-positive-integer? #f)
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(or/c exact-nonnegative-integer? #f)
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(or/c exact-positive-integer? #f)
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(or/c exact-nonnegative-integer? #f))
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(vector/c any/c
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(or/c exact-positive-integer? #f)
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(or/c exact-nonnegative-integer? #f)
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(or/c exact-positive-integer? #f)
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(or/c exact-nonnegative-integer? #f)))
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#f]
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[prop (or/c syntax? #f) #f]
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[cert (or/c syntax? #f) #f])
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syntax?]{
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Converts the @tech{datum} @scheme[v] to a @tech{syntax object}.
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The contents of pairs, vectors, and boxes, the fields of @tech{prefab}
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structures, and the values of immutable hash tables are recursively converted.
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The keys of @tech{prefab} structures and the keys of immutable hash tables are
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not converted. Mutable vectors and boxes are replaced by immutable vectors and
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boxes. For any kind of value other than a
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pair, vector, box, immutable @tech{hash table}, immutable
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@tech{prefab} structure, or @tech{syntax object}, conversion means
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wrapping the value with lexical information, source-location
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information, properties, and certificates.
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Converted objects in @scheme[v] are given the lexical context
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information of @scheme[ctxt] and the source-location information of
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@scheme[srcloc]. If @scheme[v] is not already a @tech{syntax object},
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then the resulting immediate @tech{syntax object} is given the
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properties (see @secref["stxprops"]) of @scheme[prop] and the
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@tech{inactive certificates} (see @secref["stxcerts"]) of
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@scheme[cert]; if @scheme[v] is a pair, vector, box, immutable
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@tech{hash table}, or immutable @tech{prefab} structure, recursively
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converted values are not given properties or certificates.
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Any of @scheme[ctxt], @scheme[srcloc], @scheme[prop], or @scheme[cert]
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can be @scheme[#f], in which case the resulting syntax has no lexical
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context, source information, new properties, and/or certificates.
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If @scheme[srcloc] is not @scheme[#f] or a @tech{syntax object}, it
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must be a list or vector of five elements:
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@schemeblock[
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(list source-name line column position span)
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@#,elem{or} (vector source-name line column position span)
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]
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where @scheme[source-name-v] is an arbitrary value for the source
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name; @scheme[line] is an integer for the source line, or @scheme[#f];
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@scheme[column] is an integer for the source column, or @scheme[#f];
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@scheme[position] is an integer for the source position, or
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@scheme[#f]; and @scheme[span] is an integer for the source span, or
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@scheme[#f]. The @scheme[line] and @scheme[column] values must both be
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numbers or both be @scheme[#f], otherwise the
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@exnraise[exn:fail:contract].
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Graph structure is not preserved by the conversion of @scheme[v] to a
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@tech{syntax object}. Instead, @scheme[v] is essentially unfolded into
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a tree. If @scheme[v] has a cycle through pairs, vectors, boxes,
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immutable @tech{hash tables}, and immutable @tech{prefab} structures,
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then the @exnraise[exn:fail:contract].}
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@defproc[(identifier? [v any/c]) boolean?]{
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Returns @scheme[#t] if @scheme[v] is a @tech{syntax object} and
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@scheme[(syntax-e stx)] produces a symbol.}
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@defproc[(generate-temporaries [stx-pair (or syntax? list?)])
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(listof identifier?)]{
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Returns a list of identifiers that are distinct from all other
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identifiers. The list contains as many identifiers as
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@scheme[stx-pair] contains elements. The @scheme[stx-pair] argument
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must be a syntax pair that can be flattened into a list. The elements
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of @scheme[stx-pair] can be anything, but string, symbol, keyword
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(possibly wrapped as syntax), and identifier elements will be embedded
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in the corresponding generated name, which is useful for debugging
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purposes. The generated identifiers are built with interned symbols
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(not @scheme[gensym]s), so the limitations described with
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@scheme[current-compile] do not apply.}
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@defproc[(identifier-prune-lexical-context [id-stx identifier?]
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[syms (listof symbol?) (list (syntax-e id-stx))])
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identifier?]{
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Returns an identifier with the same binding as @scheme[id-stx], but
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without lexical information from @scheme[id-stx] that does not apply
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to the symbols in @scheme[syms], where even further extension of the
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lexical information drops information for other symbols. In
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particular, transferring the lexical context via
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@scheme[datum->syntax] from the result of this function to a symbol
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other than one in @scheme[syms] produces an identifier with no binding.
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See also @scheme[quote-syntax/prune].}
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@defproc[(identifier-prune-to-source-module [id-stx identifier?])
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identifier?]{
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Returns an identifier with its lexical context minimized to that
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needed for @scheme[syntax-source-module]. The minimized lexical
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context does not include any bindings.}
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