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comparison man/lispref/variables.texi @ 314:341dac730539 r21-0b55

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Import from CVS: tag r21-0b55
author cvs
date Mon, 13 Aug 2007 10:44:22 +0200
parents 70ad99077275
children 1d62742628b6
comparison
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313:2905de29931f 314:341dac730539
93 @section Variables That Never Change 93 @section Variables That Never Change
94 @vindex nil 94 @vindex nil
95 @vindex t 95 @vindex t
96 @kindex setting-constant 96 @kindex setting-constant
97 97
98 XEmacs Lisp has two special symbols, @code{nil} and @code{t}, that 98 In XEmacs Lisp, some symbols always evaluate to themselves: the two
99 always evaluate to themselves. These symbols cannot be rebound, nor can 99 special symbols @code{nil} and @code{t}, as well as @dfn{keyword
100 their value cells be changed. An attempt to change the value of 100 symbols}, that is, symbols whose name begins with the character
101 @code{nil} or @code{t} signals a @code{setting-constant} error. 101 @samp{@code{:}}. These symbols cannot be rebound, nor can their value
102 cells be changed. An attempt to change the value of @code{nil} or
103 @code{t} signals a @code{setting-constant} error.
102 104
103 @example 105 @example
104 @group 106 @group
105 nil @equiv{} 'nil 107 nil @equiv{} 'nil
106 @result{} nil 108 @result{} nil
431 stored in the symbol's @code{variable-documentation} property. The 433 stored in the symbol's @code{variable-documentation} property. The
432 XEmacs help functions (@pxref{Documentation}) look for this property. 434 XEmacs help functions (@pxref{Documentation}) look for this property.
433 435
434 If the first character of @var{doc-string} is @samp{*}, it means that 436 If the first character of @var{doc-string} is @samp{*}, it means that
435 this variable is considered a user option. This lets users set the 437 this variable is considered a user option. This lets users set the
436 variable conventiently using the commands @code{set-variable} and 438 variable conveniently using the commands @code{set-variable} and
437 @code{edit-options}. 439 @code{edit-options}.
438 440
439 For example, this form defines @code{foo} but does not set its value: 441 For example, this form defines @code{foo} but does not set its value:
440 442
441 @example 443 @example