document latest printing convention
This commit is contained in:
Matthew Flatt
parent
b2e0d92098
commit
e5a259bdf0
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@ -442,7 +442,7 @@
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(set! src-col (syntax-column (cadr l)))
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(hash-set! next-col-map src-col dest-col)
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(set! highlight? #t)
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((loop init-line! quote-depth expr?) (cadr l) #f)
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((loop init-line! quote-depth expr? #f) (cadr l))
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(set! highlight? h?)
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(set! src-col (add1 src-col)))]
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[(and (pair? (syntax-e c))
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@ -979,27 +979,33 @@
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(define-struct forced-pair (car cdr))
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(define (quotable? v)
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(cond
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[(syntax? v) (quotable? (syntax-e v))]
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[(pair? v) (and (quotable? (car v))
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(quotable? (cdr v)))]
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[(vector? v) (andmap quotable? (vector->list v))]
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[(hash? v) (for/and ([(k v) (in-hash v)])
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(and (quotable? k)
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(quotable? v)))]
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[(box? v) (quotable? (unbox v))]
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[(and (struct? v)
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(prefab-struct-key v))
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(andmap quotable? (vector->list (struct->vector v)))]
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[(struct? v) (if (custom-write? v)
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(if (and (custom-print-as-constructor? v)
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(custom-print-as-constructor-accessor v))
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#f
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#t)
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#f)]
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[(struct-proxy? v) #f]
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[(mpair? v) #f]
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[else #t]))
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(define graph (make-hasheq))
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(let quotable? ([v v])
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(if (hash-ref graph v #f)
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#t
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(begin
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(hash-set! graph v #t)
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(cond
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[(syntax? v) (quotable? (syntax-e v))]
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[(pair? v) (and (quotable? (car v))
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(quotable? (cdr v)))]
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[(vector? v) (andmap quotable? (vector->list v))]
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[(hash? v) (for/and ([(k v) (in-hash v)])
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(and (quotable? k)
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(quotable? v)))]
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[(box? v) (quotable? (unbox v))]
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[(and (struct? v)
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(prefab-struct-key v))
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(andmap quotable? (vector->list (struct->vector v)))]
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[(struct? v) (if (custom-write? v)
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(if (and (custom-print-as-constructor? v)
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(custom-print-as-constructor-accessor v))
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#f
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#t)
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#f)]
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[(struct-proxy? v) #f]
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[(mpair? v) #f]
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[else #t])))))
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(define (do-syntax-ize v col line ht graph? qq no-cons?)
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(cond
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@ -14,8 +14,8 @@ instances of the structure type.
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The procedure for a @scheme[prop:custom-write] value takes three
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arguments: the structure to be printed, the target port, and an
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argument that is @scheme[#t] for @scheme[write] mode, @scheme[#f] for
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@scheme[display] mode, or an exact non-negative integer representing
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the current @scheme[quasiquote] depth for @scheme[print] mode. The
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@scheme[display] mode, or @scheme[0] or @scheme[1] indicating
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the current @tech{quoting depth} for @scheme[print] mode. The
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procedure should print the value to the given port using
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@scheme[write], @scheme[display], @scheme[print], @scheme[fprintf],
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@scheme[write-special], etc.
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@ -88,3 +88,16 @@ property, @scheme[#f] otherwise.}
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(custom-write? output-port? boolean?. -> . any)]{
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Returns the custom-write procedure associated with @scheme[v].}
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@deftogether[(
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@defthing[prop:custom-print-as-constructor struct-type-property?]
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@defthing[custom-print-as-constructor? struct-type-property?]
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@defthing[custom-print-as-constructor-accessor struct-type-property?]
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)]{
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A property and associated predicate and accessor. The property value
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is always a boolean. When a structure has this property as @scheme[#t]
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in addition to a @scheme[prop:custom-write] property value, then it is
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never considered @tech{quotable} for printing, which can change the
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way that enclosing datatypes are printed.}
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@ -4,34 +4,57 @@
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@title[#:tag "printing" #:style 'quiet]{The Printer}
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The default printer generally prints core datatypes in such a way that
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using @scheme[read] on the output produces a value that is
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@scheme[equal?] to the printed value---when the printed is used in
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@scheme[write]. When the printer is used in @scheme[display] mode, the
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printing of strings, byte strings, characters, and symbols changes to
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render the character/byte content directly to the output port. The
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printer's @scheme[print] mode is similar to @scheme[write], but it is
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sensitive to the @scheme[print-as-expression] parameter for printing
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values in a way that @scheme[read] plus @scheme[eval] on the output
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can be @scheme[equal?] to the printed value.
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The Racket printer support three modes:
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@itemlist[
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@item{@racket[print] mode by default prints most datatypes in such a
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way that evaluating the output as an expression produces a
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value that is @racket[equal?] to the printed value;}
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@item{@racket[write] mode prints core datatypes in such a way that
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using @racket[read] on the output produces a value that is
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@racket[equal?] to the printed value; when
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@racket[print-as-expression] is set to @racket[#f], then
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@racket[print] mode is like @racket[write] mode;}
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@item{@racket[display] mode prints core datatypes is a form in a more
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``end-user'' style rather than ``programmer' style; for
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example, a string @racket[display]s as its content characters
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without surrounding @litchar{"}s or escapes.}
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]
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When the @scheme[print-graph] parameter is set to @scheme[#t], then
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the printer first scans an object to detect cycles. The scan traverses
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the components of pairs, mutable pairs, vectors, boxes (when
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@scheme[print-box] is @scheme[#t]), hash tables (when
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@scheme[print-hash-table] is @scheme[#t]), and fields of structures
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@scheme[print-hash-table] is @scheme[#t]), fields of structures
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exposed by @scheme[struct->vector] (when @scheme[print-struct] is
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@scheme[#t]). If @scheme[print-graph] is @scheme[#t], then this
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information is used to display sharing by printing graph definitions
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and references (see @secref["parse-graph"]). If a cycle is detected in
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the initial scan, then @scheme[print-graph] is effectively set to
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@scheme[#t] automatically.
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@scheme[#t]), and fields of structures exposed by printing when the
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structure's type has the @scheme[prop:custom-write] property. If
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@scheme[print-graph] is @scheme[#t], then this information is used to
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print sharing through graph definitions and references (see
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@secref["parse-graph"]). If a cycle is detected in the initial scan,
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then @scheme[print-graph] is effectively set to @scheme[#t]
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automatically.
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With the exception of displaying byte strings, printing is defined in
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terms of Unicode characters; see @secref["ports"] for information
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on how a character stream is written to an port's underlying byte
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stream.
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In @racket[print] mode when @racket[print-as-expression] is
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@scheme[#t] (as is the default), a value prints at a @deftech{quoting
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depth} of either @scheme[0] (unquoted) or @scheme[1] (quoted). The
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initial quoting depth is accepted as an optional argument by
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@racket[print], and printing of some compound datatypes adjusts the
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print depth for component values. For example, when a list is printed
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at quoting depth @scheme[0] and all of its elements are
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@deftech{quotable}, the list is printed with a @litchar{'} prefix, and
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the list's elements are printed at quoting depth @scheme[1].
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@section[#:tag "print-symbol"]{Printing Symbols}
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Symbols containing spaces or special characters @scheme[write] using
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@ -69,16 +92,15 @@ display form of @scheme[symbol->string] applied to the symbol.
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Symbols @scheme[print] the same as they @scheme[write], unless
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@scheme[print-as-expression] is set to @scheme[#t] and the current
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@scheme[quasiquote] depth is @scheme[0]. In that case, the symbol's
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@scheme[print]ed form is prefixed with @litchar{'}. If the current
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@scheme[quasiquote] depth is @scheme[1], and if the symbol is
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@scheme['unquote] or @scheme[quasiquote], then the @scheme[print]ed
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form is prefixed with @litchar{,'}.
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@tech{quoting depth} is @scheme[0]. In that case, the symbol's
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@scheme[print]ed form is prefixed with @litchar{'}. For the purposes
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of printing enclosing datatypes, a symbol is @tech{quotable}.
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@section{Printing Numbers}
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A number prints the same way in @scheme[write], @scheme[display], and
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@scheme[print] modes.
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@scheme[print] modes. For the purposes of printing enclosing
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datatypes, a symbol is @tech{quotable}.
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A @tech{complex number} that is not a @tech{real number} always prints
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as @nonterm{m}@litchar{+}@nonterm{n}@litchar{i}, where @nonterm{m} and
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@ -107,7 +129,8 @@ printed form of its exact negation.
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The constant @scheme[#t] prints as @litchar{#t}, and the constant
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@scheme[#f] prints as @litchar{#f} in all modes (@scheme[display],
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@scheme[write], and @scheme[print]).
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@scheme[write], and @scheme[print]). For the purposes of printing
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enclosing datatypes, a symbol is @tech{quotable}.
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@section[#:tag "print-pairs"]{Printing Pairs and Lists}
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@ -130,8 +153,8 @@ printed form depends on the @scheme[cdr]:
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]
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If @scheme[print-reader-abbreviations] is set to @scheme[#t], then
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pair printing is adjusted in the case of a pair that starts a
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two-element list whose first element is @scheme[quote],
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pair printing in @scheme[write] mode is adjusted in the case of a pair
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that starts a two-element list whose first element is @scheme['quote],
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@scheme['quasiquote], @scheme['unquote], @scheme['unquote-splicing],
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@scheme['syntax], @scheme['quasisyntax], @scheme['unsyntax],
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@scheme['unsyntax-splicing]. In that case, the pair is printed with
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@ -146,28 +169,48 @@ including the tail as two elements of the enclosing list.
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The printed form of a pair is the same in both @scheme[write] and
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@scheme[display] modes, except as the printed form of the pair's
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@scheme[car] and @scheme[cdr] vary with the mode. The @scheme[print]
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form is also the same is @scheme[print-as-expression] is @scheme[#f].
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form is also the same is @scheme[print-as-expression] is @scheme[#f]
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or when the quoting depth is @scheme[1].
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When @scheme[print-as-expression] is @scheme[#t] and the current
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@scheme[quasiquote] depth is @scheme[0], then the empty list prints as
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@litchar{'()} and a pair's output is prefixed with @litchar{`}; the
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pair's content is printed at @scheme[quasiquote] depth is
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@scheme[1]. In addition, when @scheme['quasiquote], @scheme['unquote],
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or @scheme['unquote-splicing] appears as the first element of a
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two-element list, the @scheme[quasiquote] depth is adjusted
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appropriately for printing the second element of the list.
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For @scheme[print] mode when @scheme[print-as-expression] is
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@scheme[#t] and the @tech{quoting depth} is @scheme[0], then the empty
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list prints as @litchar{'()}. For a pair whose @scheme[car] and
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@scheme[cdr] are @tech{quotable}, the pair prints in @scheme[write]
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mode but with a @litchar{'} prefix; the pair's content is printed with
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@tech{quoting depth} @scheme[1]. Otherwise, when the @scheme[car] or
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@scheme[cdr] is not @tech{quotable}, then pair prints with either
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@litchar{cons} (when the @scheme[cdr] is not a pair), @litchar{list}
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(when the pair is a list), or @litchar{list*} (otherwise) after the
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openining @litchar{(}, any @litchar{.} that would otherwise be printed
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is suppressed, and the pair content is printed at @tech{quoting depth}
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@scheme[0].
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By default, mutable pairs (as created with @scheme[mcons]) print the
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same as pairs, except that @litchar["{"] and @litchar["}"] are used
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instead of @litchar{(} and @litchar{)}. Note that the reader
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treats @litchar["{"]...@litchar["}"] and @litchar{(}...@litchar{)}
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equivalently on input, creating immutable pairs in both cases.
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same as pairs for @scheme[write] and @scheme[display], except that
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@litchar["{"] and @litchar["}"] are used instead of @litchar{(} and
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@litchar{)}. Note that the reader treats @litchar["{"]...@litchar["}"]
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and @litchar{(}...@litchar{)} equivalently on input, creating
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immutable pairs in both cases. Mutable in @scheme[print] mode with
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@scheme[print-as-expression] as @scheme[#f] or a @tech{quoting depth}
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of @scheme[1] also use @litchar["{"] and @litchar["}"]. In
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@scheme[print] mode with @scheme[print-as-expression] as @scheme[#t]
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and a @tech{quoting depth} of @scheme[0], a mutable pair prints as
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@litchar{(mcons }, the @scheme[mcar] and @scheme[mcdr] printed at
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@tech{quoting depth} @scheme[0] and separated by a space, and a
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closing @litchar{)}.
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If the @scheme[print-pair-curly-braces] parameter is set to
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@scheme[#t], then immutable pairs print using @litchar["{"] and
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@litchar["}"]. If the @scheme[print-mpair-curly-braces] parameter is
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set to @scheme[#f], then mutable pairs print using @litchar{(} and
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@litchar{)}.
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@scheme[#t], then pairs print using @litchar["{"] and @litchar["}"] in
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when not using @scheme[print] mode with @scheme[print-as-expression] a
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@scheme[#t] and a @tech{quoting depth} of @scheme[0]. If the
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@scheme[print-mpair-curly-braces] parameter is set to @scheme[#f],
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then mutable pairs print using @litchar{(} and @litchar{)} in that
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mode.
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For the purposes of printing enclosing datatypes, an empty list is
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always @tech{quotable}, a pair is @tech{quotable} when its
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@scheme[car] and @scheme[cdr] are @tech{quotable}, and a mutable list
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is never @tech{quotable}.
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@section{Printing Strings}
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@ -201,6 +244,10 @@ is written using @litchar{\a}, @litchar{\b}, @litchar{\t},
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@litchar{\e} if possible, otherwise using @litchar{\} followed by one
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to three octal digits (only as many as necessary).
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For the purposes of printing enclosing datatypes, a string or a byte
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string is @tech{quotable}.
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@section[#:tag "print-vectors"]{Printing Vectors}
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In @scheme[display] mode, the printed form of a vector is @litchar{#}
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@ -212,9 +259,14 @@ element is printed only once.
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Vectors @scheme[print] the same as they @scheme[write], unless
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@scheme[print-as-expression] is set to @scheme[#t] and the current
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@scheme[quasiquote] depth is @scheme[0]. In that case, the vector's
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@scheme[print]ed form is prefixed with @litchar{`}, and its content is
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printed with @scheme[quasiquote] depth @scheme[1].
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@tech{quoting depth} is @scheme[0]. In that case, if all of the
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vector's elements are @tech{quotable}, then the vector's
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@scheme[print]ed form is prefixed with @litchar{'} and its elements
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printed with @tech{quoting depth} @scheme[1]. If its elements are not
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all @tech{quotable}, then the vector @racket[print]s as
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@litchar["(vector "], the elements at @tech{quoting depth} @scheme[0],
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and a closing @litchar{)}. A vector is @tech{quotable} when all of
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its elements are @tech{quotable}.
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@section[#:tag "print-structure"]{Printing Structures}
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@ -225,36 +277,55 @@ for which the structure is an instance:
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@itemize[
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@item{If the structure type is a @techlink{prefab} structure type,
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then it prints using @litchar{#s(} followed by the @tech{prefab}
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structure type key, then the printed form each field in the
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structure, and then @litchar{)}.
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@item{If the structure type is a @tech{prefab} structure type,
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then it prints in @scheme[write] or @scheme[display] mode using
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@litchar{#s(} followed by the @tech{prefab} structure type key,
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then the printed form each field in the structure, and then
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@litchar{)}.
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In @scheme[print] mode when @scheme[print-as-expression] is set
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to @scheme[#t] and the current @scheme[quasiquote] depth is
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@scheme[0], the structure's @scheme[print]ed form is prefixed
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with @litchar{`} and its content is printed with
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@scheme[quasiquote] depth @scheme[1].}
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to @scheme[#t] and the current @tech{quoting depth} is
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@scheme[0], if the structure's content is all @tech{quotable},
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then the structure's @scheme[print]ed form is prefixed with
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@litchar{'} and its content is printed with @tech{quoting
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depth} @scheme[1]. If any of its content is not quotable, then
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the structure type prints the same as a non-@tech{prefab}
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structure type.
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An instance of a @tech{prefab} structure type is @tech{quotable}
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when all of its content is @tech{quotable}.}
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@item{If the structure has a @scheme[prop:custom-write] property
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value, then the associated procedure is used to print the
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structure, unless the @racket[print-unreadable] parameter is
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set to @racket[#f].}
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set to @racket[#f].
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@item{If the structure type is transparent, or if any ancestor is
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transparent, then the structure prints as the vector produced
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An instance of a structure with a @scheme[prop:custom-write]
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property is @tech{quotable} if it does not have a
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@scheme[prop:custom-print-as-constructor] value as @scheme[#t]
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and its content is @tech{quotable}. The content is determined
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by the values recursively printed by the structure's
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@scheme[prop:custom-write] procedure.}
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@item{If the structure's type is transparent or if any ancestor is
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transparent (i.e,. @scheme[struct?] on the instance produces
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@scheme[#t]), then the structure prints as the vector produced
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by @scheme[struct->vector] in @scheme[display] mode, in
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@scheme[write] mode, or in @scheme[print] mode when
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@scheme[print-as-expression] is set to @scheme[#f].
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@scheme[print-as-expression] is set to @scheme[#f] or when the
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@tech{quoting depth} is @scheme[0].
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In @scheme[print] mode with @scheme[print-as-expression] as
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@scheme[#t], then the printed form is prefixed with as many
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@litchar{,}s as the current @scheme[quasiquote] depth. Instead
|
||||
of printing as a vector, the structure content is printed as a
|
||||
list, where the first element is the list is the structure's
|
||||
type name (as determined by @scheme[object-name]) printed in
|
||||
@scheme[write] mode, while the remaining elements are
|
||||
@scheme[print]ed at @scheme[quasiquote] depth @scheme[0].}
|
||||
@scheme[#t] and a @tech{quoting depth} of @scheme[0], the
|
||||
structure content is printed with a @litchar{(} followed by the
|
||||
list is the structure's type name (as determined by
|
||||
@scheme[object-name]) in @scheme[write] mode; the remaining
|
||||
elements are @scheme[print]ed at @tech{quoting depth}
|
||||
@scheme[0] and separated by a space, and finally a closing
|
||||
@litchar{)}.
|
||||
|
||||
A transparent structure type that is not a @tech{prefab}
|
||||
structure type is never @tech{quotable}.}
|
||||
|
||||
@item{For any other structure type, the structure prints as an
|
||||
unreadable value; see @secref["print-unreadable"] for more
|
||||
|
|
@ -263,75 +334,103 @@ for which the structure is an instance:
|
|||
|
||||
If the @scheme[print-struct] parameter is set to @scheme[#f], then all
|
||||
structures without a @scheme[prop:custom-write] property print as
|
||||
unreadable values.
|
||||
unreadable values (see @secref["print-unreadable"]) and count as
|
||||
@tech{quotable}.
|
||||
|
||||
|
||||
@section[#:tag "print-hashtable"]{Printing Hash Tables}
|
||||
|
||||
When the @scheme[print-hash-table] parameter is set to @scheme[#t], a
|
||||
hash table prints starting with @litchar{#hash(}, @litchar{#hasheqv(}, or @litchar{#hasheq(}
|
||||
for a table using @scheme[equal?], @scheme[eqv?], or @scheme[eq?] key comparisons,
|
||||
respectively. After this prefix, each key--value mapping is shown as
|
||||
@litchar{(}, the printed form of a key, a space, @litchar{.}, a space,
|
||||
the printed form the corresponding value, and @litchar{)}, with an
|
||||
additional space if the key--value pair is not the last to be printed.
|
||||
After all key-value pairs, the printed form completes with
|
||||
@litchar{)}.
|
||||
When the @scheme[print-hash-table] parameter is set to @scheme[#t], in
|
||||
@scheme[write] and @scheme[display] modes, a hash table prints
|
||||
starting with @litchar{#hash(}, @litchar{#hasheqv(}, or
|
||||
@litchar{#hasheq(} for a table using @scheme[equal?], @scheme[eqv?],
|
||||
or @scheme[eq?] key comparisons, respectively. After this prefix, each
|
||||
key--value mapping is shown as @litchar{(}, the printed form of a key,
|
||||
a space, @litchar{.}, a space, the printed form the corresponding
|
||||
value, and @litchar{)}, with an additional space if the key--value
|
||||
pair is not the last to be printed. After all key-value pairs, the
|
||||
printed form completes with @litchar{)}.
|
||||
|
||||
In @scheme[print] mode when @scheme[print-as-expression] is
|
||||
@scheme[#t] and the current quasiquote depth is @scheme[0], then the
|
||||
printed form is prefixed with @litchar{`} and the hash table's content
|
||||
is printed at @scheme[quasiquote] depth @scheme[1]. In the printed
|
||||
form, keys may be printed with @litchar{,} escapes, even though
|
||||
@scheme[quasiquote] does not support @scheme[unquote] escapes in the
|
||||
key position.
|
||||
@scheme[#f] or the @tech{quoting depth} is @scheme[1], the printed for
|
||||
is the same as for @scheme[write]. Otherwise, if the hash table's keys
|
||||
and values are all @tech{quotable}, the table prints with a
|
||||
@litchar{'} prefix, and the table's key and values are @racket[print]ed
|
||||
at @tech{quoting depth} @scheme[1]. If some key or value is not
|
||||
@tech{quotable}, the hash table prints as @litchar["(hash "],
|
||||
@litchar["(hasheqv "], or @litchar["(hasheq "] followed by alternating
|
||||
keys and values @racket[print]ed at @tech{quoting depth} @scheme[1] and
|
||||
separated by spaces, and finally a closing @litchar{)}. A hash table
|
||||
is @tech{quotable} when all of its keys and values are
|
||||
@tech{quotable}.
|
||||
|
||||
When the @scheme[print-hash-table] parameter is set to @scheme[#f], a
|
||||
hash table prints (un@scheme[read]ably) as @litchar{#<hash>}.
|
||||
hash table prints as @litchar{#<hash>} and counts as @tech{quotable}.
|
||||
|
||||
|
||||
@section[#:tag "print-box"]{Printing Boxes}
|
||||
|
||||
When the @scheme[print-box] parameter is set to @scheme[#t],
|
||||
a box prints as @litchar{#&} followed by the printed form of its content.
|
||||
When the @scheme[print-box] parameter is set to @scheme[#t], a box
|
||||
prints as @litchar{#&} followed by the printed form of its content in
|
||||
@scheme[write] mode, @scheme[display], or @scheme[print] mode when
|
||||
@scheme[print-as-expression] is @scheme[#f] or the @tech{quoting
|
||||
depth} is @scheme[1].
|
||||
|
||||
In @scheme[print] mode when @scheme[print-as-expression] is
|
||||
@scheme[#t] and the current quasiquote depth is @scheme[0], then the
|
||||
printed form is prefixed with @litchar{`} and the box's content
|
||||
is printed at @scheme[quasiquote] depth @scheme[1].
|
||||
@scheme[#t] and the @tech{quoting depth} is @scheme[0], a box prints
|
||||
with a @litchar{'} prefix and its value is printed at @tech{quoting
|
||||
depth} @scheme[1] when its content is @tech{quotable}, otherwise the
|
||||
box prints a @litchar["(box "] followed by the content at
|
||||
@tech{quoting depth} @scheme[0] and a closing @litchar{)}. A box is
|
||||
@tech{quotable} when its content is @tech{quotable}.
|
||||
|
||||
When the @scheme[print-box] parameter is set to @scheme[#f], a box
|
||||
prints (un@scheme[read]ably) as @litchar{#<box>}.
|
||||
prints as @litchar{#<box>} and counts as @tech{quotable}.
|
||||
|
||||
|
||||
@section{Printing Characters}
|
||||
|
||||
Characters with the special names described in
|
||||
@secref["parse-character"] @scheme[write] and @scheme[print] using the same name.
|
||||
(Some characters have multiple names; the @scheme[#\newline] and
|
||||
@scheme[#\nul] names are used instead of @scheme[#\linefeed] and
|
||||
@scheme[#\null]). Other graphic characters (according to
|
||||
@scheme[char-graphic?]) @scheme[write] as @litchar{#\} followed by the
|
||||
single character, and all others characters are written in
|
||||
@scheme[#\u] notation with four digits or @scheme[#\U] notation with
|
||||
eight digits (using the latter only if the character value it does not
|
||||
fit in four digits).
|
||||
@secref["parse-character"] @scheme[write] and @scheme[print] using the
|
||||
same name. (Some characters have multiple names; the
|
||||
@scheme[#\newline] and @scheme[#\nul] names are used instead of
|
||||
@scheme[#\linefeed] and @scheme[#\null]). Other graphic characters
|
||||
(according to @scheme[char-graphic?]) @scheme[write] as @litchar{#\}
|
||||
followed by the single character, and all others characters are
|
||||
written in @scheme[#\u] notation with four digits or @scheme[#\U]
|
||||
notation with eight digits (using the latter only if the character
|
||||
value it does not fit in four digits).
|
||||
|
||||
All characters @scheme[display] directly as themselves (i.e., a single
|
||||
character).
|
||||
|
||||
For the purposes of printing enclosing datatypes, a character is
|
||||
@tech{quotable}.
|
||||
|
||||
|
||||
@section{Printing Keywords}
|
||||
|
||||
Keywords @scheme[write], @scheme[print], and @scheme[display] the same as symbols,
|
||||
except (see @secref["print-symbol"]) with a leading @litchar{#:} (after any
|
||||
@litchar{'} prefix added in @scheme[print] mode),
|
||||
and without special handing for an initial @litchar{#} or when the
|
||||
printed form would matches a number or a delimited @litchar{.} (since
|
||||
@litchar{#:} distinguishes the keyword).
|
||||
Keywords @scheme[write], @scheme[print], and @scheme[display] the same
|
||||
as symbols, except (see @secref["print-symbol"]) with a leading
|
||||
@litchar{#:} (after any @litchar{'} prefix added in @scheme[print]
|
||||
mode), and without special handing for an initial @litchar{#} or when
|
||||
the printed form would matches a number or a delimited @litchar{.}
|
||||
(since @litchar{#:} distinguishes the keyword).
|
||||
|
||||
For the purposes of printing enclosing datatypes, a keyword is
|
||||
@tech{quotable}.
|
||||
|
||||
|
||||
@section{Printing Regular Expressions}
|
||||
|
||||
Regexp values in all modes (@scheme[write], @scheme[display], and @scheme[print])
|
||||
starting with @litchar{#px} (for @scheme[pregexp]-based regexps) or
|
||||
@litchar{#rx} (for @scheme[regexp]-based regexps) followed by the
|
||||
@scheme[write] form of the regexp's source string or byte string.
|
||||
Regexp values in all modes (@scheme[write], @scheme[display], and
|
||||
@scheme[print]) starting with @litchar{#px} (for
|
||||
@scheme[pregexp]-based regexps) or @litchar{#rx} (for
|
||||
@scheme[regexp]-based regexps) followed by the @scheme[write] form of
|
||||
the regexp's source string or byte string.
|
||||
|
||||
For the purposes of printing enclosing datatypes, a regexp value is
|
||||
@tech{quotable}.
|
||||
|
||||
|
||||
@section[#:tag "print-unreadable"]{Printing Unreadable Values}
|
||||
|
|
@ -343,3 +442,6 @@ form is @litchar{#<}@nonterm{something}@litchar{>}, where
|
|||
to the value itself. If @racket[print-unreadable] is set to
|
||||
@racket[#f], then attempting to print an unreadable value raises
|
||||
@racket[exn:fail].
|
||||
|
||||
For the purposes of printing enclosing datatypes, a value that prints
|
||||
unreadably nevertheless counts as @tech{quotable}.
|
||||
|
|
|
|||
|
|
@ -157,6 +157,11 @@
|
|||
(ptest "#0='(#0#\n \"iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii\"\n #0#)"
|
||||
(read (open-input-string "#0=(#0# \"iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii\" #0#)")))
|
||||
|
||||
(ptest "''a" ''a)
|
||||
(ptest "'`a" '`a)
|
||||
(ptest "'`,#,#`a" '`,#,#`a)
|
||||
(ptest "'`,#,#`,@#,@a" '`,#,#`,@#,@a)
|
||||
|
||||
(void))
|
||||
|
||||
(report-errs)
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user