@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990-1995, 1998-1999, 2001-2014 Free Software
+@c Copyright (C) 1990-1995, 1998-1999, 2001-2015 Free Software
@c Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@node 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,
* Byte-Code Type:: A function written in Lisp, then compiled.
* Autoload Type:: A type used for automatically loading seldom-used
functions.
+* Finalizer Type:: Runs code when no longer reachable.
+
@end menu
@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}}
@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.
@code{autoload}, which stores the object in the function cell of a
symbol. @xref{Autoload}, for more details.
+@node Finalizer Type
+@subsection Finalizer Type
+
+ A @dfn{finalizer object} helps Lisp code clean up after objects that
+are no longer needed. A finalizer holds a Lisp function object.
+When a finalizer object becomes unreachable after a garbage collection
+pass, Emacs calls the finalizer's associated function object.
+When deciding whether a finalizer is reachable, Emacs does not count
+references from finalizer objects themselves, allowing you to use
+finalizers without having to worry about accidentally capturing
+references to finalized objects themselves.
+
+Errors in finalizers are printed to @code{*Messages*}. Emacs runs
+a given finalizer object's associated function exactly once, even
+if that function fails.
+
+@defun make-finalizer function
+Make a finalizer that will run @var{function}. @var{function} will be
+called after garbage collection when the returned finalizer object
+becomes unreachable. If the finalizer object is reachable only
+through references from finalizer objects, it does not count as
+reachable for the purpose of deciding whether to run @var{function}.
+@var{function} will be run once per finalizer object.
+@end defun
+
@node Editing Types
@section Editing Types
@cindex editing types
@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}.
This function returns a symbol naming the primitive type of
@var{object}. The value is one of the symbols @code{bool-vector},
@code{buffer}, @code{char-table}, @code{compiled-function},
-@code{cons}, @code{float}, @code{font-entity}, @code{font-object},
-@code{font-spec}, @code{frame}, @code{hash-table}, @code{integer},
-@code{marker}, @code{overlay}, @code{process}, @code{string},
-@code{subr}, @code{symbol}, @code{vector}, @code{window}, or
-@code{window-configuration}.
+@code{cons}, @code{finalizer}, @code{float}, @code{font-entity},
+@code{font-object}, @code{font-spec}, @code{frame}, @code{hash-table},
+@code{integer}, @code{marker}, @code{overlay}, @code{process},
+@code{string}, @code{subr}, @code{symbol}, @code{vector},
+@code{window}, or @code{window-configuration}.
@example
(type-of 1)
@example
@group
-(equal "asdf" (propertize "asdf" '(asdf t)))
+(equal "asdf" (propertize "asdf" 'asdf t))
@result{} t
@end group
@group
(equal-including-properties "asdf"
- (propertize "asdf" '(asdf t)))
+ (propertize "asdf" 'asdf t))
@result{} nil
@end group
@end example