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comparison man/lispref/objects.texi @ 4471:2d39535e1f9d

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Say explicitly that eq is useful for chars; xref number comparison, lispref 2008-05-27 Aidan Kehoe <kehoea@parhasard.net> * lispref/objects.texi (Equality Predicates): Cross reference to the section on comparison of numbers when talking about using #'eq with integers; also mention that #'eq gives t when passed identical integers, and that #'char= is also available there.
author Aidan Kehoe <kehoea@parhasard.net>
date Tue, 27 May 2008 11:58:42 +0200
parents dc697b1b786f
children a99eb40f0b5b
comparison
equal deleted inserted replaced
4470:c76b1bc6bd28 4471:2d39535e1f9d
2244 This function returns @code{t} if @var{object1} and @var{object2} are 2244 This function returns @code{t} if @var{object1} and @var{object2} are
2245 the same object, @code{nil} otherwise. The ``same object'' means that a 2245 the same object, @code{nil} otherwise. The ``same object'' means that a
2246 change in one will be reflected by the same change in the other. 2246 change in one will be reflected by the same change in the other.
2247 2247
2248 @code{eq} returns @code{t} if @var{object1} and @var{object2} are 2248 @code{eq} returns @code{t} if @var{object1} and @var{object2} are
2249 integers with the same value. Also, since symbol names are normally 2249 integers with the same value. It is preferable to use @code{=} or
2250 unique, if the arguments are symbols with the same name, they are 2250 @code{eql} in many contexts for numeric comparison; @pxref{Comparison of
2251 @code{eq}. For other types (e.g., lists, vectors, strings), two 2251 Numbers}. @code{eq} also returns @code{t} if @var{object1} and
2252 arguments with the same contents or elements are not necessarily 2252 @var{object2} are identical characters, though in this case you may
2253 @code{eq} to each other: they are @code{eq} only if they are the same 2253 prefer to use @code{char=}.
2254 object. 2254
2255 Also, since symbol names are normally unique, if the arguments are
2256 symbols with the same name, they are @code{eq}. For other types (e.g.,
2257 lists, vectors, strings), two arguments with the same contents or
2258 elements are not necessarily @code{eq} to each other: they are @code{eq}
2259 only if they are the same object.
2255 2260
2256 (The @code{make-symbol} function returns an uninterned symbol that is 2261 (The @code{make-symbol} function returns an uninterned symbol that is
2257 not interned in the standard @code{obarray}. When uninterned symbols 2262 not interned in the standard @code{obarray}. When uninterned symbols
2258 are in use, symbol names are no longer unique. Distinct symbols with 2263 are in use, symbol names are no longer unique. Distinct symbols with
2259 the same name are not @code{eq}. @xref{Creating Symbols}.) 2264 the same name are not @code{eq}. @xref{Creating Symbols}.)
2260 2265
2261 NOTE: Under XEmacs 19, characters are really just integers, and thus 2266 NOTE: Under XEmacs 19, characters are really just integers, and thus
2262 characters and integers are @code{eq}. Under XEmacs 20, it was 2267 characters and integers with the same numeric are @code{eq}. Under
2263 necessary to preserve remnants of this in function such as @code{old-eq} 2268 XEmacs 20, it was necessary to preserve remnants of this in function
2264 in order to maintain byte-code compatibility. Byte code compiled 2269 such as @code{old-eq} in order to maintain byte-code compatibility.
2265 under any Emacs 19 will automatically have calls to @code{eq} mapped 2270 Byte code compiled under any Emacs 19 will automatically have calls to
2266 to @code{old-eq} when executed under XEmacs 20. 2271 @code{eq} mapped to @code{old-eq} when executed under XEmacs 20.
2267 2272
2268 @example 2273 @example
2269 @group 2274 @group
2270 (eq 'foo 'foo) 2275 (eq 'foo 'foo)
2271 @result{} t 2276 @result{} t