Common Lisp FORMAT Reference - CLHS Summary (HexstreamSoft)

Overview

This page summarizes CLHS 22.3 "Formatted Output" with sections on directive definitions and additional FORMAT operation information. Users can employ V (dynamic argument) or # (remaining parameters count) as prefix parameters.

Directive Reference Table

22.3.1 Basic Output

Directive	Name	Prefix Args	: modifier	@ modifier	Consumption
~C	Character	--	Spells out non-printing chars	#\ reader syntax	1 arg
~%	Newline	n (repeat count)	--	--	0 args
~&	Fresh-Line	n (repeat count)	--	--	0 args
~\|	Page	n (repeat count)	--	--	0 args
~~	Tilde	n (repeat count)	--	--	0 args

22.3.2 Radix Control

Directive	Name	Prefix Args	: modifier	@ modifier	Consumption
~R	Radix	radix, mincol, padchar, commachar, comma-interval	With radix: commas; Without: ordinal / old Roman	With radix: sign; Without: cardinal as words / Roman	1 arg
~D	Decimal	mincol, padchar, commachar, comma-interval	Commas between groups	Force sign	1 arg
~B	Binary	mincol, padchar, commachar, comma-interval	Commas between groups	Force sign	1 arg
~O	Octal	mincol, padchar, commachar, comma-interval	Commas between groups	Force sign	1 arg
~X	Hexadecimal	mincol, padchar, commachar, comma-interval	Commas between groups	Force sign	1 arg

22.3.3 Floating-Point Printers

Directive	Name	Prefix Args	: modifier	@ modifier
~F	Fixed-Format	w, d, k, overflowchar, padchar	--	Force sign
~E	Exponential	w, d, e, k, overflowchar, padchar, exponentchar	--	Force sign
~G	General	w, d, e, k, overflowchar, padchar, exponentchar	--	Force sign
~$	Monetary	d, n, w, padchar	Sign before padding	Force sign

22.3.4 Printer Operations

Directive	Name	Prefix Args	: modifier	@ modifier
~A	Aesthetic (princ)	mincol, colinc, minpad, padchar	nil prints as "()"	Pad on left
~S	Standard (prin1)	mincol, colinc, minpad, padchar	nil prints as "()"	Pad on left
~W	Write	--	*print-pretty* = t	*print-level* = nil, *print-length* = nil

22.3.5 Pretty Printer Operations

Directive	Name	Notes
~_	Conditional Newline	: = fill, @ = miser, :@ = mandatory, plain = linear
~<...~:>	Logical Block	Up to 3 segments (prefix, body, suffix) via ~;
~I	Indent	n (default 0); : = current mode, plain = block mode
~/name/	Call Function	Calls named function with (stream arg colon-p at-sign-p &rest params)

22.3.6 Layout Control

Directive	Name	Prefix Args	Notes
~T	Tabulate	colnum, colinc	@ = relative; : = section-relative (pretty printer)
~<...~>	Justification	mincol, colinc, minpad, padchar	: = space before first; @ = space after last
~>	End Justification	--	Terminates ~<

22.3.7 Control Flow

Directive	Name	Notes
~*	Go-To	Skip n args; ~:* = back up n; ~n@* = absolute position
~[...~]	Conditional	Ordinal selection by index; ~:[false~;true~]; ~@[if-true~]
~]	End Conditional	Terminates ~[
~{...~}	Iteration	: = sublists; @ = remaining args; :@ = remaining args as sublists
~}	End Iteration	Terminates ~{; ~:} forces at least one iteration
~?	Recursive Processing	Consumes control string + arg list; ~@? uses remaining args

22.3.8 Miscellaneous Operations

Directive	Name	Notes
~(...~)	Case Conversion	plain = downcase; : = capitalize words; @ = capitalize first; :@ = upcase
~)	End Case Conversion	Terminates ~(
~P	Plural	"s"/nothing; @ = "y"/"ies"; : = back up one arg first

22.3.9 Pseudo-Operations

Directive	Name	Notes
~;	Clause Separator	Used in ~[ and ~< constructs only
~^	Escape Upward	0 params = test remaining args; 1 = zero test; 2 = equal test; 3 = range test
~<newline>	Ignored Newline	plain = ignore newline+whitespace; : = ignore newline only; @ = keep newline, ignore whitespace

Additional Information (22.3.10)

Nesting Requirements

Directive invocations must maintain proper nesting structure.

Missing and Additional Arguments

"Consequences are undefined if no arg remains for a directive requiring an argument. However, it is permissible for one or more args to remain unprocessed by a directive; such args are ignored."

Parameter Limits

"Consequences are undefined if a format directive is given more parameters than described as accepting."

Modifier Combinations

"Consequences are undefined if colon or at-sign modifiers are given to a directive in a combination not specifically described as meaningful."