From 4e5ac4b0c611571d3e7930a27693a3fe03be1f40 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Mon, 17 Feb 2020 13:36:50 -0800 Subject: Reorder discussion of integer basics * doc/lispref/numbers.texi (Integer Basics): Put the fixnum/bignum discussion at the end of the section, not at the start (Bug#39557). --- doc/lispref/numbers.texi | 77 +++++++++++++++++++++++++----------------------- 1 file changed, 40 insertions(+), 37 deletions(-) diff --git a/doc/lispref/numbers.texi b/doc/lispref/numbers.texi index c8941eab736..4b9fdf24206 100644 --- a/doc/lispref/numbers.texi +++ b/doc/lispref/numbers.texi @@ -34,39 +34,6 @@ numbers have a fixed amount of precision. @node Integer Basics @section Integer Basics - Integers in Emacs Lisp are not limited to the machine word size. - - Under the hood, though, there are two kinds of integers: smaller -ones, called @dfn{fixnums}, and larger ones, called @dfn{bignums}. -Some functions in Emacs accept only fixnums. Also, while fixnums can -be compared for numeric equality with @code{eq}, bignums require -more-heavyweight equality predicates like @code{eql} and @code{=}. - - The range of values for bignums is limited by the amount of main -memory, by machine characteristics such as the size of the word used -to represent a bignum's exponent, and by the @code{integer-width} -variable. These limits are typically much more generous than the -limits for fixnums. A bignum is never numerically equal to a fixnum; -if Emacs computes an integer in fixnum range, it represents the -integer as a fixnum, not a bignum. - - The range of values for a fixnum depends on the machine. The -minimum range is @minus{}536,870,912 to 536,870,911 (30 bits; i.e., -@ifnottex -@minus{}2**29 -@end ifnottex -@tex -@math{-2^{29}} -@end tex -to -@ifnottex -2**29 @minus{} 1), -@end ifnottex -@tex -@math{2^{29}-1}), -@end tex -but many machines provide a wider range. - The Lisp reader reads an integer as a nonempty sequence of decimal digits with optional initial sign and optional final period. @@ -145,6 +112,46 @@ arguments to such functions may be either numbers or markers, we often give these arguments the name @var{number-or-marker}. When the argument value is a marker, its position value is used and its buffer is ignored. + In Emacs Lisp, text characters are represented by integers. Any +integer between zero and the value of @code{(max-char)}, inclusive, is +considered to be valid as a character. @xref{Character Codes}. + + Integers in Emacs Lisp are not limited to the machine word size. +Under the hood, though, there are two kinds of integers: smaller ones, +called @dfn{fixnums}, and larger ones, called @dfn{bignums}. Although +Emacs Lisp code ordinarily should not depend on whether an integer is +a fixnum or a bignum, older Emacs versions support only fixnums, some +functions in Emacs still accept only fixnums, and older Emacs Lisp +code may have trouble when given bignums. For example, while older +Emacs Lisp code could safely compare integers for numeric equality +with @code{eq}, the presence of bignums means that equality predicates +like @code{eql} and @code{=} should now be used to compare integers. + + The range of values for bignums is limited by the amount of main +memory, by machine characteristics such as the size of the word used +to represent a bignum's exponent, and by the @code{integer-width} +variable. These limits are typically much more generous than the +limits for fixnums. A bignum is never numerically equal to a fixnum; +if Emacs computes an integer in fixnum range, it represents the +integer as a fixnum, not a bignum. + + The range of values for a fixnum depends on the machine. The +minimum range is @minus{}536,870,912 to 536,870,911 (30 bits; i.e., +@ifnottex +@minus{}2**29 +@end ifnottex +@tex +@math{-2^{29}} +@end tex +to +@ifnottex +2**29 @minus{} 1), +@end ifnottex +@tex +@math{2^{29}-1}), +@end tex +but many machines provide a wider range. + @cindex largest fixnum @cindex maximum fixnum @defvar most-positive-fixnum @@ -207,10 +214,6 @@ Setting this variable to a large number can be costly if a computation creates huge integers. @end defvar - In Emacs Lisp, text characters are represented by integers. Any -integer between zero and the value of @code{(max-char)}, inclusive, is -considered to be valid as a character. @xref{Character Codes}. - @node Float Basics @section Floating-Point Basics -- cgit v1.2.1