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change install-converting-printer to set print-as-expression to #f

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and update docs to make sense relative to Racket's default printer
This commit is contained in:
Matthew Flatt 2010-08-19 06:20:52 -06:00
parent e55f0cade1
commit 716949f499
2 changed files with 17 additions and 8 deletions
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1
collects/mzlib/pconvert.rkt
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@ -576,6 +576,7 @@
(current-print (lambda (v)
(unless (void? v)
(print (print-convert v))))))
(print-as-expression #f)
(current-prompt-read (lambda ()
(display (current-read-eval-convert-print-prompt))
(read-syntax 'STDIN))))))

24
collects/mzlib/scribblings/pconvert.scrbl
View File

@ -7,15 +7,21 @@
@mzlib[#:mode title pconvert]
The @schememodname[mzlib/pconvert] library defines routines for
printing Scheme values as @scheme[eval]uable S-expressions, rather
than @scheme[read]able S-expressions.
printing Scheme values as @scheme[eval]uable S-expressions. Racket's
default printing mode also prints values as expressions (in contrast
to the Lisp and Scheme tradition of printing @scheme[read]able
S-expressions), but @schememodname[mzlib/pconvert] is more
configurable and approximates expressions for a wider range of
values. For example, procedures print using @schemeresultfont{lambda}
instead of @schemeresultfont{#<procedure>}.
The @scheme[print-convert] procedure does not print values; rather, it
converts a Scheme value into another Scheme value such that the new
value pretty-prints as a Scheme expression that evaluates to the
original value. For example, @scheme[(pretty-print (print-convert `(9
,(box 5) #(6 7))))] prints the literal expression @schemeresult[(list
9 (box 5) (vector 6 7))] to the current output port.
value @racket[pretty-write]s as a Scheme expression that evaluates to
the original value. For example, @scheme[(pretty-write (print-convert
`(9 ,(box 5) #(6 7))))] prints the literal expression
@schemeresult[(list 9 (box 5) (vector 6 7))] to the current output
port.
To install print converting into the read-eval-print loop, require
@scheme[mzlib/pconvert] and call the procedure
@ -182,8 +188,10 @@ might return the list
@defproc[(install-converting-printer) void?]{
Sets the current print handler to print values using
@scheme[print-convert]. The current read handler is also set to use
the prompt returned by
@scheme[print-convert] and sets @racket[print-as-expression] to
@racket[#f] (since the conversion of a value is meant to be printed in
@racket[read]able form rather than @racket[eval]uable form). The
current read handler is also set to use the prompt returned by
@scheme[current-read-eval-convert-print-prompt].}