Merge: Document wide integers better.

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