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improve docs on printer modes

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This commit is contained in:
Matthew Flatt 2010-05-09 07:05:08 -06:00
parent d9917b27a0
commit f24d66f02f
1 changed files with 21 additions and 19 deletions
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40
collects/scribblings/reference/printer.scrbl
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@ -4,27 +4,39 @@
@title[#:tag "printing" #:style 'quiet]{The Printer} @title[#:tag "printing" #:style 'quiet]{The Printer}
The Racket printer support three modes: The Racket printer supports three modes:
@itemlist[ @itemlist[
@item{@racket[print] mode by default prints most datatypes in such a
way that evaluating the output as an expression produces a
value that is @racket[equal?] to the printed value;}
@item{@racket[write] mode prints core datatypes in such a way that @item{@racket[write] mode prints core datatypes in such a way that
using @racket[read] on the output produces a value that is using @racket[read] on the output produces a value that is
@racket[equal?] to the printed value; when @racket[equal?] to the printed value;}
@racket[print-as-expression] is set to @racket[#f], then
@racket[print] mode is like @racket[write] mode;}
@item{@racket[display] mode prints core datatypes is a form in a more @item{@racket[display] mode prints core datatypes is a form in a more
``end-user'' style rather than ``programmer' style; for ``end-user'' style rather than ``programmer' style; for
example, a string @racket[display]s as its content characters example, a string @racket[display]s as its content characters
without surrounding @litchar{"}s or escapes.} without surrounding @litchar{"}s or escapes;}
@item{@racket[print] mode by default---when
@scheme[print-as-expression] is @scheme[#t]---prints most
datatypes in such a way that evaluating the output as an
expression produces a value that is @racket[equal?] to the
printed value; when @racket[print-as-expression] is set to
@racket[#f], then @racket[print] mode is like @racket[write]
mode.}
] ]
In @racket[print] mode when @racket[print-as-expression] is
@scheme[#t] (as is the default), a value prints at a @deftech{quoting
depth} of either @scheme[0] (unquoted) or @scheme[1] (quoted). The
initial quoting depth is accepted as an optional argument by
@racket[print], and printing of some compound datatypes adjusts the
print depth for component values. For example, when a list is printed
at quoting depth @scheme[0] and all of its elements are
@deftech{quotable}, the list is printed with a @litchar{'} prefix, and
the list's elements are printed at quoting depth @scheme[1].
When the @scheme[print-graph] parameter is set to @scheme[#t], then When the @scheme[print-graph] parameter is set to @scheme[#t], then
the printer first scans an object to detect cycles. The scan traverses the printer first scans an object to detect cycles. The scan traverses
the components of pairs, mutable pairs, vectors, boxes (when the components of pairs, mutable pairs, vectors, boxes (when
@ -44,16 +56,6 @@ terms of Unicode characters; see @secref["ports"] for information
on how a character stream is written to an port's underlying byte on how a character stream is written to an port's underlying byte
stream. stream.
In @racket[print] mode when @racket[print-as-expression] is
@scheme[#t] (as is the default), a value prints at a @deftech{quoting
depth} of either @scheme[0] (unquoted) or @scheme[1] (quoted). The
initial quoting depth is accepted as an optional argument by
@racket[print], and printing of some compound datatypes adjusts the
print depth for component values. For example, when a list is printed
at quoting depth @scheme[0] and all of its elements are
@deftech{quotable}, the list is printed with a @litchar{'} prefix, and
the list's elements are printed at quoting depth @scheme[1].
@section[#:tag "print-symbol"]{Printing Symbols} @section[#:tag "print-symbol"]{Printing Symbols}