Commit 68018641 authored by Paul Eggert's avatar Paul Eggert
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[etc/ChangeLog]

* NEWS: Integer overflow now yields floating-point instead of
wrapping around.
[doc/lispref/ChangeLog]
* numbers.texi (Arithmetic Operations, Math Functions): Large integers go to
floats instead of wrapping around.
* objects.texi (Integer Type): Likewise.
parent 4ed0cebd
2011-05-03 Paul Eggert <eggert@cs.ucla.edu>
* numbers.texi (Integer Basics): Large integers are treated as floats.
(Arithmetic Operations, Math Functions): Large integers go to
floats instead of wrapping around.
* objects.texi (Integer Type): Likewise.
2011-04-30 Lars Magne Ingebrigtsen <larsi@gnus.org>
......
......@@ -507,9 +507,9 @@ commonly used.
All of these functions except @code{%} return a floating point value
if any argument is floating.
It is important to note that in Emacs Lisp, arithmetic functions
do not check for overflow. Thus @code{(1+ 268435455)} may evaluate to
@minus{}268435456, depending on your hardware.
If integer arithmetic overflows, the resulting value is converted
to floating point. Thus @code{(1+ 536870911)} may evaluate to
536870912.0, depending on your hardware.
@defun 1+ number-or-marker
This function returns @var{number-or-marker} plus 1.
......@@ -826,7 +826,7 @@ On the other hand, shifting one place to the right looks like this:
As the example illustrates, shifting one place to the right divides the
value of a positive integer by two, rounding downward.
The function @code{lsh}, like all Emacs Lisp arithmetic functions, does
The function @code{lsh} does
not check for overflow, so shifting left can discard significant bits
and change the sign of the number. For example, left shifting
536,870,911 produces @minus{}2 on a 30-bit machine:
......@@ -1169,8 +1169,8 @@ approximately.
@defun expt x y
This function returns @var{x} raised to power @var{y}. If both
arguments are integers and @var{y} is positive, the result is an
integer; in this case, overflow causes truncation, so watch out.
arguments are integers and @var{y} is nonnegative, the result is an
integer if it is in Emacs integer range.
@end defun
@defun sqrt arg
......
......@@ -179,10 +179,10 @@ to
@tex
@math{2^{29}-1})
@end tex
on most machines. (Some machines may provide a wider range.) It is
important to note that the Emacs Lisp arithmetic functions do not check
for overflow. Thus @code{(1+ 536870911)} is @minus{}536870912 on most
machines.
on most machines. (Some machines may provide a wider range.)
If integer arithmetic overflows, the resulting value is converted
+to floating point. Thus @code{(1+ 536870911)} may evaluate to
+536870912.0, depending on your hardware.
The read syntax for integers is a sequence of (base ten) digits with an
optional sign at the beginning and an optional period at the end. The
......@@ -195,7 +195,8 @@ leading @samp{+} or a final @samp{.}.
1 ; @r{The integer 1.}
1. ; @r{Also the integer 1.}
+1 ; @r{Also the integer 1.}
1073741825 ; @r{Also the integer 1 on a 30-bit implementation.}
1073741825 ; @r{The floating point number 1073741825.0,}
; @r{on a 30-bit implementation.}
@end group
@end example
......
2011-05-03 Paul Eggert <eggert@cs.ucla.edu>
* NEWS: Integer overflow now yields floating-point instead of
wrapping around.
2011-05-03 Leo Liu <sdl.web@gmail.com>
* NEWS: Mention the new command isearch-yank-pop.
......
......@@ -728,6 +728,12 @@ soap-inspect.el is an interactive inspector for SOAP WSDL structures.
* Incompatible Lisp Changes in Emacs 24.1
+++
** Integer arithmetic overflow now yields the nearest floating-piont
value rather than wrapping around. For example, on a 32-bit machine,
(1+ 536870911) yields 536870912.0, instead of the -536870912 it
yielded in Emacs 23.3, or the 0 it yielded in Emacs 23.1.
---
** `char-direction-table' and the associated function `char-direction'
were deleted. They were buggy and inferior to the new support of
......
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