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Showing content from https://docs.racket-lang.org/reference/Writing.html below:

13.5 Writing

Writes

to

, normally in such a way that instances of core datatypes can be read back in. If

has a handler associated to it via

, then the handler is called. Otherwise, the

is used (in

mode), as configured by various parameters.

See The Printer for more information about the default printer. In particular, note that write may require memory proportional to the depth of the value being printed, due to the initial cycle check.

Examples:

Displays

to

, similar to

, but usually in such a way that byte- and character-based datatypes are written as raw bytes or characters. If

has a handler associated to it via

, then the handler is called. Otherwise, the

is used (in

mode), as configured by various parameters.

See The Printer for more information about the default printer. In particular, note that display may require memory proportional to the depth of the value being printed, due to the initial cycle check.

The optional quote-depth argument adjusts printing when the print-as-expression parameter is set to #t. In that case, quote-depth specifies the starting quote depth for printing datum.

The rationale for providing print is that display and write both have specific output conventions, and those conventions restrict the ways that an environment can change the behavior of display and write procedures. No output conventions should be assumed for print, so that environments are free to modify the actual output generated by print in any way.

Added in version 6.1.1.8 of package base.

The same as

followed by

, which is similar to

in Pascal or Java.

The same as

followed by

.

The println function is not equivalent to println in other languages, because println uses printing conventions that are closer to write than to display. For a closer analog to println in other languages, use displayln.

Added in version 6.1.1.8 of package base.

Prints formatted output to out, where form is a string that is printed directly, except for special formatting escapes:

• ~n or ~% prints a newline character (which is equivalent to \n in a literal format string)

• ~a or ~A displays the next argument among the vs

• ~s or ~S writes the next argument among the vs

• ~v or ~V prints the next argument among the vs

• ~.‹c› where ‹c› is a, A, s, S, v, or V: truncates default-handler display, write, or print output to (error-print-width) characters, using ... as the last three characters if the untruncated output would be longer

• ~e or ~E outputs the next argument among the vs using the current error value conversion handler (see error-value->string-handler) and current error printing width

• ~c or ~C write-chars the next argument in vs; if the next argument is not a character, the exn:fail:contract exception is raised

• ~b or ~B prints the next argument among the vs in binary; if the next argument is not an exact number, the exn:fail:contract exception is raised

• ~o or ~O prints the next argument among the vs in octal; if the next argument is not an exact number, the exn:fail:contract exception is raised

• ~x or ~X prints the next argument among the vs in hexadecimal; if the next argument is not an exact number, the exn:fail:contract exception is raised

• ~~ prints a tilde.

• ~‹w›, where ‹w› is a whitespace character (see char-whitespace?), skips characters in form until a non-whitespace character is encountered or until a second end-of-line is encountered (whichever happens first). On all platforms, an end-of-line can be #\return, #\newline, or #\return followed immediately by #\newline.

The form string must not contain any ~ that is not one of the above escapes, otherwise the exn:fail:contract exception is raised. When the format string requires more vs than are supplied, the exn:fail:contract exception is raised. Similarly, when more vs are supplied than are used by the format string, the exn:fail:contract exception is raised.

Example:

(3 4) as a string is "(3 4)".

Formats to a string. The result is the same as

Example:

> (format "~a as a string is ~s.\n" '(3 4) "(3 4)")

"(3 4) as a string is \"(3 4)\".\n"

A

that controls pair printing. If the value is true, then pairs print using

and

instead of

and

. The default is

.

A

that controls pair printing. If the value is true, then mutable pairs print using

and

instead of

and

. The default is

.

A

that controls printing data with sharing; defaults to

. See

for more information.

A

that controls printing structure values in vector or

form; defaults to

. See

for more information. This parameter has no effect on the printing of structures that have a custom-write procedure (see

).

A

that controls printing of booleans. When the parameter’s value is true,

and

print as

and

, otherwise they print as

and

. The default is

.

A

that controls printing of two-element lists that start with

,

,

,

,

,

,

, or

; defaults to

. See

for more information.

A

that controls printing of

. Up to

characters are used to show the datum form of a syntax object within

...

(after the

’s source location, if any), where

is used as the last three characters if the printed form would otherwise be longer than

characters. A value of

for

means that the datum is not shown at all.

A

that contains a recommendation for the number of columns that should be used for printing values via

. May or may not be respected by

- the current default handler for

does not. It is expected that REPLs that use some form of pretty-printing for values respect this parameter.

Added in version 8.0.0.13 of package base.

A

that is used when writing compiled code (see

) that contains pathname literals, including source-location pathnames for procedure names. When the parameter’s value is a

, paths that syntactically extend

are converted to relative paths; when the resulting compiled code is read, relative paths are converted back to complete paths using the

parameter (if it is not

; otherwise, the path is left relative). When the parameter’s value is

, then paths that syntactically extend

are converted as relative to

; the

must extend

, in which case

path elements (in the sense of

) may be used to make a path relative to

.

Gets or sets the

,

, or

for

. This handler is called to output to the port when

,

, or

(respectively) is applied to the port. Each handler must accept two arguments: the value to be printed and the destination port. The handler’s return value is ignored.

A port print handler optionally accepts a third argument, which corresponds to the optional third argument to print; if a procedure given to port-print-handler does not accept a third argument, it is wrapped with a procedure that discards the optional third argument.

The default port display and write handlers print Racket expressions with Racket’s built-in printer (see The Printer). The default print handler calls the global port print handler (the value of the global-port-print-handler parameter); the default global port print handler is the same as the default write handler.

A global port print handler optionally accepts a third argument, which corresponds to the optional third argument to print. If a procedure given to global-port-print-handler does not accept a third argument, it is wrapped with a procedure that discards the optional third argument.

Added in version 8.8.0.6 of package base.

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