diff options
| -rw-r--r-- | doc/emacs/ChangeLog | 7 | ||||
| -rw-r--r-- | doc/emacs/buffers.texi | 7 | ||||
| -rw-r--r-- | doc/emacs/files.texi | 3 | ||||
| -rw-r--r-- | doc/lispref/ChangeLog | 12 | ||||
| -rw-r--r-- | doc/lispref/files.texi | 7 | ||||
| -rw-r--r-- | doc/lispref/numbers.texi | 117 | ||||
| -rw-r--r-- | doc/lispref/objects.texi | 12 | ||||
| -rw-r--r-- | doc/lispref/os.texi | 8 |
8 files changed, 99 insertions, 74 deletions
diff --git a/doc/emacs/ChangeLog b/doc/emacs/ChangeLog index 89a78263e94..6e69a96a2a8 100644 --- a/doc/emacs/ChangeLog +++ b/doc/emacs/ChangeLog @@ -1,3 +1,10 @@ +2011-06-02 Paul Eggert <eggert@cs.ucla.edu> + + Document wide integers better. + * buffers.texi (Buffers): + * files.texi (Visiting): Document maxima for 64-bit machines, + and mention virtual memory limits. + 2011-05-28 Chong Yidong <cyd@stupidchicken.com> * custom.texi (Hooks): Reorganize. Mention Prog mode. diff --git a/doc/emacs/buffers.texi b/doc/emacs/buffers.texi index ae0d85f249b..d4cc4f7bb6a 100644 --- a/doc/emacs/buffers.texi +++ b/doc/emacs/buffers.texi @@ -43,8 +43,11 @@ can be different from the value in other buffers. @xref{Locals}. A buffer's size cannot be larger than some maximum, which is defined by the largest buffer position representable by the @dfn{Emacs integer} data type. This is because Emacs tracks buffer positions -using that data type. For 32-bit machines, the largest buffer size is -512 megabytes. +using that data type. For typical 64-bit machines, the maximum buffer size +enforced by the data types is @math{2^61 - 2} bytes, or about 2 EiB. +For typical 32-bit machines, the maximum is @math{2^29 - 2} bytes, or +about 512 MiB. Buffer sizes are also limited by the size of Emacs's +virtual memory. @menu * Select Buffer:: Creating a new buffer or reselecting an old one. diff --git a/doc/emacs/files.texi b/doc/emacs/files.texi index 40bd065610c..793a11e62ed 100644 --- a/doc/emacs/files.texi +++ b/doc/emacs/files.texi @@ -209,7 +209,8 @@ to reread it. about 10 megabytes), Emacs asks you for confirmation first. You can answer @kbd{y} to proceed with visiting the file. Note, however, that Emacs cannot visit files that are larger than the maximum Emacs buffer -size, which is around 512 megabytes on 32-bit machines +size, which is limited by the amount of memory Emacs can allocate +and by the integers that Emacs can represent (@pxref{Buffers}). If you try, Emacs will display an error message saying that the maximum buffer size has been exceeded. diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog index 83cee10f899..54ad6abdb07 100644 --- a/doc/lispref/ChangeLog +++ b/doc/lispref/ChangeLog @@ -1,3 +1,15 @@ +2011-06-03 Paul Eggert <eggert@cs.ucla.edu> + + Document wide integers better. + * files.texi (File Attributes): Document ino_t values better. + ino_t values no longer map to anything larger than a single cons. + * numbers.texi (Integer Basics, Integer Basics, Arithmetic Operations): + (Bitwise Operations): + * objects.texi (Integer Type): Use a binary notation that is a bit easier + to read, and that will port better if 62-bits becomes the default. + Fix or remove incorrect examples. + * os.texi (Time Conversion): Document time_t values better. + 2011-05-31 Lars Magne Ingebrigtsen <larsi@gnus.org> * processes.texi (Process Information): Document diff --git a/doc/lispref/files.texi b/doc/lispref/files.texi index 72f39f681ae..4d992bd2c51 100644 --- a/doc/lispref/files.texi +++ b/doc/lispref/files.texi @@ -1237,11 +1237,12 @@ deleted and recreated; @code{nil} otherwise. @item The file's inode number. If possible, this is an integer. If the inode number is too large to be represented as an integer in Emacs -Lisp, but still fits into a 32-bit integer, then the value has the +Lisp but dividing it by @math{2^16} yields a representable integer, +then the value has the form @code{(@var{high} . @var{low})}, where @var{low} holds the low 16 -bits. If the inode is wider than 32 bits, the value is of the form +bits. If the inode number is too wide for even that, the value is of the form @code{(@var{high} @var{middle} . @var{low})}, where @code{high} holds -the high 24 bits, @var{middle} the next 24 bits, and @var{low} the low +the high bits, @var{middle} the middle 24 bits, and @var{low} the low 16 bits. @item diff --git a/doc/lispref/numbers.texi b/doc/lispref/numbers.texi index 2c73a03a26c..65921f444e0 100644 --- a/doc/lispref/numbers.texi +++ b/doc/lispref/numbers.texi @@ -50,8 +50,9 @@ to @tex @math{2^{29}-1}), @end tex -but some machines may provide a wider range. Many examples in this -chapter assume an integer has 30 bits. +but some machines provide a wider range. Many examples in this +chapter assume that an integer has 30 bits and that floating point +numbers are IEEE double precision. @cindex overflow The Lisp reader reads an integer as a sequence of digits with optional @@ -97,17 +98,18 @@ view the numbers in their binary form. In 30-bit binary, the decimal integer 5 looks like this: @example -00 0000 0000 0000 0000 0000 0000 0101 +0000...000101 (30 bits total) @end example @noindent -(We have inserted spaces between groups of 4 bits, and two spaces -between groups of 8 bits, to make the binary integer easier to read.) +(The @samp{...} stands for enough bits to fill out a 30-bit word; in +this case, @samp{...} stands for twenty 0 bits. Later examples also +use the @samp{...} notation to make binary integers easier to read.) The integer @minus{}1 looks like this: @example -11 1111 1111 1111 1111 1111 1111 1111 +1111...111111 (30 bits total) @end example @noindent @@ -120,14 +122,14 @@ complement} notation.) @minus{}5 looks like this: @example -11 1111 1111 1111 1111 1111 1111 1011 +1111...111011 (30 bits total) @end example In this implementation, the largest 30-bit binary integer value is 536,870,911 in decimal. In binary, it looks like this: @example -01 1111 1111 1111 1111 1111 1111 1111 +0111...111111 (30 bits total) @end example Since the arithmetic functions do not check whether integers go @@ -137,7 +139,7 @@ negative integer @minus{}536,870,912: @example (+ 1 536870911) @result{} -536870912 - @result{} 10 0000 0000 0000 0000 0000 0000 0000 + @result{} 1000...000000 (30 bits total) @end example Many of the functions described in this chapter accept markers for @@ -508,8 +510,8 @@ commonly used. 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. +do not check for overflow. Thus @code{(1+ 536870911)} may evaluate to +@minus{}536870912, depending on your hardware. @defun 1+ number-or-marker This function returns @var{number-or-marker} plus 1. @@ -829,19 +831,19 @@ value of a positive integer by two, rounding downward. The function @code{lsh}, like all Emacs Lisp arithmetic functions, 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: +536,870,911 produces @minus{}2 in the 30-bit implementation: @example (lsh 536870911 1) ; @r{left shift} @result{} -2 @end example -In binary, in the 30-bit implementation, the argument looks like this: +In binary, the argument looks like this: @example @group ;; @r{Decimal 536,870,911} -01 1111 1111 1111 1111 1111 1111 1111 +0111...111111 (30 bits total) @end group @end example @@ -851,7 +853,7 @@ which becomes the following when left shifted: @example @group ;; @r{Decimal @minus{}2} -11 1111 1111 1111 1111 1111 1111 1110 +1111...111110 (30 bits total) @end group @end example @end defun @@ -874,9 +876,9 @@ looks like this: @group (ash -6 -1) @result{} -3 ;; @r{Decimal @minus{}6 becomes decimal @minus{}3.} -11 1111 1111 1111 1111 1111 1111 1010 +1111...111010 (30 bits total) @result{} -11 1111 1111 1111 1111 1111 1111 1101 +1111...111101 (30 bits total) @end group @end example @@ -887,9 +889,9 @@ In contrast, shifting the pattern of bits one place to the right with @group (lsh -6 -1) @result{} 536870909 ;; @r{Decimal @minus{}6 becomes decimal 536,870,909.} -11 1111 1111 1111 1111 1111 1111 1010 +1111...111010 (30 bits total) @result{} -01 1111 1111 1111 1111 1111 1111 1101 +0111...111101 (30 bits total) @end group @end example @@ -899,34 +901,35 @@ Here are other examples: @c with smallbook but not with regular book! --rjc 16mar92 @smallexample @group - ; @r{ 30-bit binary values} + ; @r{ 30-bit binary values} -(lsh 5 2) ; 5 = @r{00 0000 0000 0000 0000 0000 0000 0101} - @result{} 20 ; = @r{00 0000 0000 0000 0000 0000 0001 0100} +(lsh 5 2) ; 5 = @r{0000...000101} + @result{} 20 ; = @r{0000...010100} @end group @group (ash 5 2) @result{} 20 -(lsh -5 2) ; -5 = @r{11 1111 1111 1111 1111 1111 1111 1011} - @result{} -20 ; = @r{11 1111 1111 1111 1111 1111 1110 1100} +(lsh -5 2) ; -5 = @r{1111...111011} + @result{} -20 ; = @r{1111...101100} (ash -5 2) @result{} -20 @end group @group -(lsh 5 -2) ; 5 = @r{00 0000 0000 0000 0000 0000 0000 0101} - @result{} 1 ; = @r{00 0000 0000 0000 0000 0000 0000 0001} +(lsh 5 -2) ; 5 = @r{0000...000101} + @result{} 1 ; = @r{0000...000001} @end group @group (ash 5 -2) @result{} 1 @end group @group -(lsh -5 -2) ; -5 = @r{11 1111 1111 1111 1111 1111 1111 1011} - @result{} 268435454 ; = @r{00 0111 1111 1111 1111 1111 1111 1110} +(lsh -5 -2) ; -5 = @r{1111...111011} + @result{} 268435454 + ; = @r{0011...111110} @end group @group -(ash -5 -2) ; -5 = @r{11 1111 1111 1111 1111 1111 1111 1011} - @result{} -2 ; = @r{11 1111 1111 1111 1111 1111 1111 1110} +(ash -5 -2) ; -5 = @r{1111...111011} + @result{} -2 ; = @r{1111...111110} @end group @end smallexample @end defun @@ -961,23 +964,23 @@ because its binary representation consists entirely of ones. If @smallexample @group - ; @r{ 30-bit binary values} + ; @r{ 30-bit binary values} -(logand 14 13) ; 14 = @r{00 0000 0000 0000 0000 0000 0000 1110} - ; 13 = @r{00 0000 0000 0000 0000 0000 0000 1101} - @result{} 12 ; 12 = @r{00 0000 0000 0000 0000 0000 0000 1100} +(logand 14 13) ; 14 = @r{0000...001110} + ; 13 = @r{0000...001101} + @result{} 12 ; 12 = @r{0000...001100} @end group @group -(logand 14 13 4) ; 14 = @r{00 0000 0000 0000 0000 0000 0000 1110} - ; 13 = @r{00 0000 0000 0000 0000 0000 0000 1101} - ; 4 = @r{00 0000 0000 0000 0000 0000 0000 0100} - @result{} 4 ; 4 = @r{00 0000 0000 0000 0000 0000 0000 0100} +(logand 14 13 4) ; 14 = @r{0000...001110} + ; 13 = @r{0000...001101} + ; 4 = @r{0000...000100} + @result{} 4 ; 4 = @r{0000...000100} @end group @group (logand) - @result{} -1 ; -1 = @r{11 1111 1111 1111 1111 1111 1111 1111} + @result{} -1 ; -1 = @r{1111...111111} @end group @end smallexample @end defun @@ -991,18 +994,18 @@ passed just one argument, it returns that argument. @smallexample @group - ; @r{ 30-bit binary values} + ; @r{ 30-bit binary values} -(logior 12 5) ; 12 = @r{00 0000 0000 0000 0000 0000 0000 1100} - ; 5 = @r{00 0000 0000 0000 0000 0000 0000 0101} - @result{} 13 ; 13 = @r{00 0000 0000 0000 0000 0000 0000 1101} +(logior 12 5) ; 12 = @r{0000...001100} + ; 5 = @r{0000...000101} + @result{} 13 ; 13 = @r{0000...001101} @end group @group -(logior 12 5 7) ; 12 = @r{00 0000 0000 0000 0000 0000 0000 1100} - ; 5 = @r{00 0000 0000 0000 0000 0000 0000 0101} - ; 7 = @r{00 0000 0000 0000 0000 0000 0000 0111} - @result{} 15 ; 15 = @r{00 0000 0000 0000 0000 0000 0000 1111} +(logior 12 5 7) ; 12 = @r{0000...001100} + ; 5 = @r{0000...000101} + ; 7 = @r{0000...000111} + @result{} 15 ; 15 = @r{0000...001111} @end group @end smallexample @end defun @@ -1016,18 +1019,18 @@ result is 0, which is an identity element for this operation. If @smallexample @group - ; @r{ 30-bit binary values} + ; @r{ 30-bit binary values} -(logxor 12 5) ; 12 = @r{00 0000 0000 0000 0000 0000 0000 1100} - ; 5 = @r{00 0000 0000 0000 0000 0000 0000 0101} - @result{} 9 ; 9 = @r{00 0000 0000 0000 0000 0000 0000 1001} +(logxor 12 5) ; 12 = @r{0000...001100} + ; 5 = @r{0000...000101} + @result{} 9 ; 9 = @r{0000...001001} @end group @group -(logxor 12 5 7) ; 12 = @r{00 0000 0000 0000 0000 0000 0000 1100} - ; 5 = @r{00 0000 0000 0000 0000 0000 0000 0101} - ; 7 = @r{00 0000 0000 0000 0000 0000 0000 0111} - @result{} 14 ; 14 = @r{00 0000 0000 0000 0000 0000 0000 1110} +(logxor 12 5 7) ; 12 = @r{0000...001100} + ; 5 = @r{0000...000101} + ; 7 = @r{0000...000111} + @result{} 14 ; 14 = @r{0000...001110} @end group @end smallexample @end defun @@ -1040,9 +1043,9 @@ bit is one in the result if, and only if, the @var{n}th bit is zero in @example (lognot 5) @result{} -6 -;; 5 = @r{00 0000 0000 0000 0000 0000 0000 0101} +;; 5 = @r{0000...000101} (30 bits total) ;; @r{becomes} -;; -6 = @r{11 1111 1111 1111 1111 1111 1111 1010} +;; -6 = @r{1111...111010} (30 bits total) @end example @end defun diff --git a/doc/lispref/objects.texi b/doc/lispref/objects.texi index c58d54f13fc..27d9ba10aef 100644 --- a/doc/lispref/objects.texi +++ b/doc/lispref/objects.texi @@ -179,10 +179,9 @@ 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 typical 32-bit machines. (Some machines provide a wider range.) +Emacs Lisp arithmetic functions do not check for overflow. Thus +@code{(1+ 536870911)} is @minus{}536870912 if Emacs integers are 30 bits. 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 +194,6 @@ 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.} @end group @end example @@ -203,8 +201,8 @@ leading @samp{+} or a final @samp{.}. As a special exception, if a sequence of digits specifies an integer too large or too small to be a valid integer object, the Lisp reader reads it as a floating-point number (@pxref{Floating Point Type}). -For instance, on most machines @code{536870912} is read as the -floating-point number @code{536870912.0}. +For instance, if Emacs integers are 30 bits, @code{536870912} is read +as the floating-point number @code{536870912.0}. @xref{Numbers}, for more information. diff --git a/doc/lispref/os.texi b/doc/lispref/os.texi index b226d676462..5f422065c5b 100644 --- a/doc/lispref/os.texi +++ b/doc/lispref/os.texi @@ -1193,11 +1193,11 @@ to calendrical information and vice versa. You can get time values from the functions @code{current-time} (@pxref{Time of Day}) and @code{file-attributes} (@pxref{Definition of file-attributes}). - Many operating systems are limited to time values that contain 32 bits + Many 32-bit operating systems are limited to time values that contain 32 bits of information; these systems typically handle only the times from -1901-12-13 20:45:52 UTC through 2038-01-19 03:14:07 UTC. However, some -operating systems have larger time values, and can represent times far -in the past or future. +1901-12-13 20:45:52 UTC through 2038-01-19 03:14:07 UTC. However, 64-bit +and some 32-bit operating systems have larger time values, and can +represent times far in the past or future. Time conversion functions always use the Gregorian calendar, even for dates before the Gregorian calendar was introduced. Year numbers |