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comparison man/lispref/objects.texi @ 4472:a99eb40f0b5b

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Correct an omitted word, expand on bignum equality in the lispref. 2008-05-29 Aidan Kehoe <kehoea@parhasard.net> * lispref/objects.texi (Equality Predicates): Expand on bignum equality; correct an omitted word in the last commit.
author Aidan Kehoe <kehoea@parhasard.net>
date Thu, 29 May 2008 18:53:45 +0200
parents 2d39535e1f9d
children f9104f0e9b91
comparison
equal deleted inserted replaced
4471:2d39535e1f9d 4472:a99eb40f0b5b
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. It is preferable to use @code{=} or 2249 integers with the same value. It is preferable to use @code{=} or
2250 @code{eql} in many contexts for numeric comparison; @pxref{Comparison of 2250 @code{eql} in many contexts for numeric comparison, especially since
2251 Numbers}. @code{eq} also returns @code{t} if @var{object1} and 2251 bignums (integers with values that would have otherwise overflowed, only
2252 @var{object2} are identical characters, though in this case you may 2252 available on some builds) with the same value are not @code{eq};
2253 prefer to use @code{char=}. 2253 @pxref{Comparison of Numbers}. @code{eq} also returns @code{t} if
2254 @var{object1} and @var{object2} are identical characters, though in this
2255 case you may prefer to use @code{char=}.
2254 2256
2255 Also, since symbol names are normally unique, if the arguments are 2257 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., 2258 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 2259 lists, vectors, strings), two arguments with the same contents or
2258 elements are not necessarily @code{eq} to each other: they are @code{eq} 2260 elements are not necessarily @code{eq} to each other: they are @code{eq}
2262 not interned in the standard @code{obarray}. When uninterned symbols 2264 not interned in the standard @code{obarray}. When uninterned symbols
2263 are in use, symbol names are no longer unique. Distinct symbols with 2265 are in use, symbol names are no longer unique. Distinct symbols with
2264 the same name are not @code{eq}. @xref{Creating Symbols}.) 2266 the same name are not @code{eq}. @xref{Creating Symbols}.)
2265 2267
2266 NOTE: Under XEmacs 19, characters are really just integers, and thus 2268 NOTE: Under XEmacs 19, characters are really just integers, and thus
2267 characters and integers with the same numeric are @code{eq}. Under 2269 characters and integers with the same numeric code are @code{eq}. Under
2268 XEmacs 20, it was necessary to preserve remnants of this in function 2270 XEmacs 20, it was necessary to preserve remnants of this in function
2269 such as @code{old-eq} in order to maintain byte-code compatibility. 2271 such as @code{old-eq} in order to maintain byte-code compatibility.
2270 Byte code compiled under any Emacs 19 will automatically have calls to 2272 Byte code compiled under any Emacs 19 will automatically have calls to
2271 @code{eq} mapped to @code{old-eq} when executed under XEmacs 20. 2273 @code{eq} mapped to @code{old-eq} when executed under XEmacs 20.
2272 2274