@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990-1995, 1998-1999, 2001-2012
-@c Free Software Foundation, Inc.
+@c Copyright (C) 1990-1995, 1998-1999, 2001-2014 Free Software
+@c Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@node Lisp Data Types
@chapter Lisp Data Types
@menu
* Integer Type:: Numbers without fractional parts.
-* Floating Point Type:: Numbers with fractional parts and with a large range.
+* Floating-Point Type:: Numbers with fractional parts and with a large range.
* Character Type:: The representation of letters, numbers and
control characters.
* Symbol Type:: A multi-use object that refers to a function,
@node Integer Type
@subsection Integer Type
- The range of values for integers in Emacs Lisp is @minus{}536870912 to
-536870911 (30 bits; i.e.,
+ The range of values for an integer depends on the machine. The
+minimum range is @minus{}536,870,912 to 536,870,911 (30 bits; i.e.,
@ifnottex
--2**29
+@minus{}2**29
@end ifnottex
@tex
@math{-2^{29}}
@end tex
to
@ifnottex
-2**29 - 1)
+2**29 @minus{} 1)
@end ifnottex
@tex
@math{2^{29}-1})
@end tex
-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.
+but many machines provide a wider range.
+Emacs Lisp arithmetic functions do not check for integer overflow. Thus
+@code{(1+ 536870911)} is @minus{}536,870,912 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
@example
@group
--1 ; @r{The integer -1.}
+-1 ; @r{The integer @minus{}1.}
1 ; @r{The integer 1.}
1. ; @r{Also the integer 1.}
+1 ; @r{Also the integer 1.}
@noindent
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}).
+reads it as a floating-point number (@pxref{Floating-Point Type}).
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.
-@node Floating Point Type
-@subsection Floating Point Type
+@node Floating-Point Type
+@subsection Floating-Point Type
- Floating point numbers are the computer equivalent of scientific
-notation; you can think of a floating point number as a fraction
+ Floating-point numbers are the computer equivalent of scientific
+notation; you can think of a floating-point number as a fraction
together with a power of ten. The precise number of significant
figures and the range of possible exponents is machine-specific; Emacs
uses the C data type @code{double} to store the value, and internally
this records a power of 2 rather than a power of 10.
- The printed representation for floating point numbers requires either
+ The printed representation for floating-point numbers requires either
a decimal point (with at least one digit following), an exponent, or
-both. For example, @samp{1500.0}, @samp{15e2}, @samp{15.0e2},
-@samp{1.5e3}, and @samp{.15e4} are five ways of writing a floating point
+both. For example, @samp{1500.0}, @samp{+15e2}, @samp{15.0e+2},
+@samp{+1500000e-3}, and @samp{.15e4} are five ways of writing a floating-point
number whose value is 1500. They are all equivalent.
@xref{Numbers}, for more information.
@end quotation
Here are several examples of symbol names. Note that the @samp{+} in
-the fifth example is escaped to prevent it from being read as a number.
-This is not necessary in the fourth example because the rest of the name
+the fourth example is escaped to prevent it from being read as a number.
+This is not necessary in the sixth example because the rest of the name
makes it invalid as a number.
@example
characters in Emacs strings: multibyte and unibyte (@pxref{Text
Representations}). Roughly speaking, unibyte strings store raw bytes,
while multibyte strings store human-readable text. Each character in
-a unibyte string is a byte, i.e.@: its value is between 0 and 255. By
+a unibyte string is a byte, i.e., its value is between 0 and 255. By
contrast, each character in a multibyte string may have a value
between 0 to 4194303 (@pxref{Character Type}). In both cases,
characters above 127 are non-@acronym{ASCII}.
octal escape sequences (@samp{\@var{n}}) in string constants.
@strong{But beware:} If a string constant contains hexadecimal or
octal escape sequences, and these escape sequences all specify unibyte
-characters (i.e.@: less than 256), and there are no other literal
+characters (i.e., less than 256), and there are no other literal
non-@acronym{ASCII} characters or Unicode-style escape sequences in
the string, then Emacs automatically assumes that it is a unibyte
string. That is to say, it assumes that all non-@acronym{ASCII}
special purposes. A char-table can also specify a single value for
a whole character set.
+@cindex @samp{#^} read syntax
The printed representation of a char-table is like a vector
-except that there is an extra @samp{#^} at the beginning.
+except that there is an extra @samp{#^} at the beginning.@footnote{You
+may also encounter @samp{#^^}, used for ``sub-char-tables''.}
@xref{Char-Tables}, for special functions to operate on char-tables.
Uses of char-tables include:
derived from ``subroutine''.) Most primitive functions evaluate all
their arguments when they are called. A primitive function that does
not evaluate all its arguments is called a @dfn{special form}
-(@pxref{Special Forms}).@refill
+(@pxref{Special Forms}).
It does not matter to the caller of a function whether the function is
primitive. However, this does matter if you try to redefine a primitive
redefinition of primitive functions}.
The term @dfn{function} refers to all Emacs functions, whether written
-in Lisp or C. @xref{Function Type}, for information about the
+in Lisp or C@. @xref{Function Type}, for information about the
functions written in Lisp.
Primitive functions have no read syntax and print in hash notation
@item custom-variable-p
@xref{Variable Definitions, custom-variable-p}.
-@item display-table-p
-@xref{Display Tables, display-table-p}.
-
@item floatp
@xref{Predicates on Numbers, floatp}.
Here we describe functions that test for equality between two
objects. Other functions test equality of contents between objects of
-specific types, e.g.@: strings. For these predicates, see the
+specific types, e.g., strings. For these predicates, see the
appropriate chapter describing the data type.
@defun eq object1 object2
the same object, and @code{nil} otherwise.
If @var{object1} and @var{object2} are integers with the same value,
-they are considered to be the same object (i.e.@: @code{eq} returns
+they are considered to be the same object (i.e., @code{eq} returns
@code{t}). If @var{object1} and @var{object2} are symbols with the
same name, they are normally the same object---but see @ref{Creating
-Symbols} for exceptions. For other types (e.g.@: lists, vectors,
+Symbols} for exceptions. For other types (e.g., lists, vectors,
strings), two arguments with the same contents or elements are not
necessarily @code{eq} to each other: they are @code{eq} only if they
are the same object, meaning that a change in the contents of one will