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comparison man/cl.texi @ 257:65c19d2020f7 r20-5b27

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Import from CVS: tag r20-5b27
author cvs
date Mon, 13 Aug 2007 10:22:03 +0200
parents 3d6bfa290dbd
children 11cf20601dec
comparison
equal deleted inserted replaced
256:19076a51efde 257:65c19d2020f7
519 This function takes a @code{:need} keyword argument, but also 519 This function takes a @code{:need} keyword argument, but also
520 accepts other keyword arguments which are passed on to the 520 accepts other keyword arguments which are passed on to the
521 @code{member*} function. @code{allow-other-keys} is used to 521 @code{member*} function. @code{allow-other-keys} is used to
522 keep both @code{find-thing} and @code{member*} from complaining 522 keep both @code{find-thing} and @code{member*} from complaining
523 about each others' keywords in the arguments. 523 about each others' keywords in the arguments.
524
525 In Common Lisp, keywords are recognized by the Lisp parser itself
526 and treated as special entities. In Emacs, keywords are just
527 symbols whose names begin with colons, which @code{defun*} has
528 arranged to set equal to themselves so that they will essentially
529 be self-quoting.
530 524
531 As a (significant) performance optimization, this package 525 As a (significant) performance optimization, this package
532 implements the scan for keyword arguments by calling @code{memq} 526 implements the scan for keyword arguments by calling @code{memq}
533 to search for keywords in a ``rest'' argument. Technically 527 to search for keywords in a ``rest'' argument. Technically
534 speaking, this is incorrect, since @code{memq} looks at the 528 speaking, this is incorrect, since @code{memq} looks at the
5590 @end example 5584 @end example
5591 5585
5592 Lucid Emacs supports @code{#'} notation starting with version 19.8. 5586 Lucid Emacs supports @code{#'} notation starting with version 19.8.
5593 5587
5594 @item 5588 @item
5595 The ``backquote'' feature uses a different syntax in Emacs Lisp.
5596
5597 @example
5598 (defmacro foo (v &rest body) `(let ((,v 0)) @@,body)) ; Common Lisp
5599 (defmacro foo (v &rest body) (` (let (((, v) 0)) (@@, body))) ; Emacs
5600 @end example
5601
5602 @item
5603 Reader macros. Common Lisp includes a second type of macro that 5589 Reader macros. Common Lisp includes a second type of macro that
5604 works at the level of individual characters. For example, Common 5590 works at the level of individual characters. For example, Common
5605 Lisp implements the quote notation by a reader macro called @code{'}, 5591 Lisp implements the quote notation by a reader macro called @code{'},
5606 whereas Emacs Lisp's parser just treats quote as a special case. 5592 whereas Emacs Lisp's parser just treats quote as a special case.
5607 Some Lisp packages use reader macros to create special syntaxes 5593 Some Lisp packages use reader macros to create special syntaxes
5608 for themselves, which the Emacs parser is incapable of reading. 5594 for themselves, which the Emacs parser is incapable of reading.
5609
5610 The lack of reader macros, incidentally, is the reason behind
5611 Emacs Lisp's unusual backquote syntax. Since backquotes are
5612 implemented as a Lisp package and not built-in to the Emacs
5613 parser, they are forced to use a regular macro named @code{`}
5614 which is used with the standard function/macro call notation.
5615 5595
5616 @item 5596 @item
5617 Other syntactic features. Common Lisp provides a number of 5597 Other syntactic features. Common Lisp provides a number of
5618 notations beginning with @code{#} that the Emacs Lisp parser 5598 notations beginning with @code{#} that the Emacs Lisp parser
5619 won't understand. For example, @samp{#| ... |#} is an 5599 won't understand. For example, @samp{#| ... |#} is an
5620 alternate comment notation, and @samp{#+lucid (foo)} tells 5600 alternate comment notation, and @samp{#+lucid (foo)} tells
5621 the parser to ignore the @code{(foo)} except in Lucid Common 5601 the parser to ignore the @code{(foo)} except in Lucid Common
5622 Lisp. 5602 Lisp.
5603
5604 The number prefixes `#b', `#o', and `#x', however, are supported
5605 by the Emacs Lisp parser to represent numbers in binary, octal,
5606 and hexadecimal notation (or radix), just like in Common Lisp.
5623 5607
5624 @item 5608 @item
5625 Packages. In Common Lisp, symbols are divided into @dfn{packages}. 5609 Packages. In Common Lisp, symbols are divided into @dfn{packages}.
5626 Symbols that are Lisp built-ins are typically stored in one package; 5610 Symbols that are Lisp built-ins are typically stored in one package;
5627 symbols that are vendor extensions are put in another, and each 5611 symbols that are vendor extensions are put in another, and each