CLHS: Function WRITE, PRIN1, PRINT, PPRINT...

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Function WRITE, PRIN1, PRINT, PPRINT, PRINC

Syntax:

write object `&key` array base case circle escape gensym length level lines miser-width pprint-dispatch pretty radix readably right-margin stream

=> object

prin1 object `&optional` output-stream => object

princ object `&optional` output-stream => object

print object `&optional` output-stream => object

pprint object `&optional` output-stream => <no values>

Arguments and Values:

object---an object.

output-stream---an output stream designator. The default is standard output.

array---a generalized boolean.

base---a radix.

case---a symbol of type `(member :upcase :downcase :capitalize)`.

circle---a generalized boolean.

escape---a generalized boolean.

gensym---a generalized boolean.

length---a non-negative integer, or nil.

level---a non-negative integer, or nil.

lines---a non-negative integer, or nil.

miser-width---a non-negative integer, or nil.

pprint-dispatch---a pprint dispatch table.

pretty---a generalized boolean.

radix---a generalized boolean.

readably---a generalized boolean.

right-margin---a non-negative integer, or nil.

stream---an output stream designator. The default is standard output.

Description:

write, prin1, princ, print, and pprint write the printed representation of object to output-stream.

write is the general entry point to the Lisp printer. For each explicitly supplied keyword parameter named in the next figure, the corresponding printer control variable is dynamically bound to its value while printing goes on; for each keyword parameter in the next figure that is not explicitly supplied, the value of the corresponding printer control variable is the same as it was at the time write was invoked. Once the appropriate bindings are established, the object is output by the Lisp printer.

    Parameter        Corresponding Dynamic Variable
    array            *print-array*
    base             *print-base*
    case             *print-case*
    circle           *print-circle*
    escape           *print-escape*
    gensym           *print-gensym*
    length           *print-length*
    level            *print-level*
    lines            *print-lines*
    miser-width      *print-miser-width*
    pprint-dispatch  *print-pprint-dispatch*
    pretty           *print-pretty*
    radix            *print-radix*
    readably         *print-readably*
    right-margin     *print-right-margin*

Figure 22-7. Argument correspondences for the WRITE function.

prin1, princ, print, and pprint implicitly bind certain print parameters to particular values. The remaining parameter values are taken from *print-array*, *print-base*, *print-case*, *print-circle*, *print-escape*, *print-gensym*, *print-length*, *print-level*, *print-lines*, *print-miser-width*, *print-pprint-dispatch*, *print-pretty*, *print-radix*, and *print-right-margin*.

prin1 produces output suitable for input to read. It binds *print-escape* to true.

princ is just like prin1 except that the output has no escape characters. It binds *print-escape* to false and *print-readably* to false. The general rule is that output from princ is intended to look good to people, while output from prin1 is intended to be acceptable to read.

print is just like prin1 except that the printed representation of object is preceded by a newline and followed by a space.

pprint is just like print except that the trailing space is omitted and object is printed with the *print-pretty* flag non-nil to produce pretty output.

Output-stream specifies the stream to which output is to be sent.

Affected By:

*standard-output*, *terminal-io*, *print-escape*, *print-radix*, *print-base*, *print-circle*, *print-pretty*, *print-level*, *print-length*, *print-case*, *print-gensym*, *print-array*, *read-default-float-format*.

Exceptional Situations: None.

See Also:

readtable-case, Section 22.3.4 (FORMAT Printer Operations)

Notes:

The functions prin1 and print do not bind *print-readably*.

     (prin1 object output-stream)
    ==  (write object :stream output-stream :escape t)

     (princ object output-stream)
    ==  (write object stream output-stream :escape nil :readably nil)

     (print object output-stream)
    ==  (progn (terpri output-stream)
               (write object :stream output-stream
                             :escape t)
               (write-char #\space output-stream))

     (pprint object output-stream)
    ==  (write object :stream output-stream :escape t :pretty t)

The following X3J13 cleanup issues, not part of the specification, apply to this section:

- PRINC-READABLY:X3J13-DEC-91
- PRETTY-PRINT-INTERFACE

Copyright 1996-2005, LispWorks Ltd. All rights reserved.