@copying
This file documents the GNU Emacs Common Lisp emulation package.
-Copyright @copyright{} 1993, 2001-2012 Free Software Foundation, Inc.
+Copyright @copyright{} 1993, 2001--2013 Free Software Foundation, Inc.
@quotation
Permission is granted to copy, distribute and/or modify this document
is included in the section entitled ``GNU Free Documentation License''.
(a) The FSF's Back-Cover Text is: ``You have the freedom to copy and
-modify this GNU manual. Buying copies from the FSF supports it in
-developing GNU and promoting software freedom.''
+modify this GNU manual.''
@end quotation
@end copying
@item
Some features are too complex or bulky relative to their benefit
to Emacs Lisp programmers. CLOS and Common Lisp streams are fine
-examples of this group.
+examples of this group. (The separate package EIEIO implements
+a subset of CLOS functionality. @xref{Top, , Introduction, eieio, EIEIO}.)
@item
Other features cannot be implemented without modification to the
defines aliases to the @file{cl-lib.el} definitions). Where
@file{cl-lib.el} defines a function called, for example,
@code{cl-incf}, @file{cl.el} uses the same name but without the
-@samp{cl-} prefix, e.g.@: @code{incf} in this example. There are a few
+@samp{cl-} prefix, e.g., @code{incf} in this example. There are a few
exceptions to this. First, functions such as @code{cl-defun} where
the unprefixed version was already used for a standard Emacs Lisp
function. In such cases, the @file{cl.el} version adds a @samp{*}
-suffix, e.g.@: @code{defun*}. Second, there are some obsolete features
+suffix, e.g., @code{defun*}. Second, there are some obsolete features
that are only implemented in @file{cl.el}, not in @file{cl-lib.el},
because they are replaced by other standard Emacs Lisp features.
Finally, in a very few cases the old @file{cl.el} versions do not
@node Setf Extensions
@subsection Setf Extensions
-Several standard (e.g.@: @code{car}) and Emacs-specific
-(e.g.@: @code{window-point}) Lisp functions are @code{setf}-able by default.
+Several standard (e.g., @code{car}) and Emacs-specific
+(e.g., @code{window-point}) Lisp functions are @code{setf}-able by default.
This package defines @code{setf} handlers for several additional functions:
@itemize
The generalized variable @code{buffer-substring}, listed above,
also works in this way by replacing a portion of the current buffer.
-@c FIXME? Also `eq'? (see cl-lib.el)
+@c FIXME? Also `eq'? (see cl-lib.el)
@c Currently commented out in cl.el.
@ignore
@xref{Obsolete Setf Customization}.
@end ignore
+@c FIXME? Is this still true?
@item
A macro call, in which case the macro is expanded and @code{setf}
is applied to the resulting form.
-
-@item
-Any form for which a @code{defsetf} or @code{define-setf-method}
-has been made. @xref{Obsolete Setf Customization}.
@end itemize
@c FIXME should this be in lispref? It seems self-evident.
bound on entry, it is simply made unbound by @code{makunbound} or
@code{fmakunbound} on exit.
@end ignore
-
-Note that the @file{cl.el} version of this macro behaves slightly
-differently. @xref{Obsolete Macros}.
@end defmac
@defmac cl-letf* (bindings@dots{}) forms@dots{}
accordingly for the duration of the body of the @code{cl-flet}; then
the old function definition, or lack thereof, is restored.
-You can use @code{cl-flet} to disable or modify the behavior of a
-function in a temporary fashion. (Compare this with the idea
-of advising functions.
+You can use @code{cl-flet} to disable or modify the behavior of
+functions (including Emacs primitives) in a temporary, localized fashion.
+(Compare this with the idea of advising functions.
@xref{Advising Functions,,,elisp,GNU Emacs Lisp Reference Manual}.)
-This will even work on Emacs primitives, although note that some calls
-to primitive functions internal to Emacs are made without going
-through the symbol's function cell, and so will not be affected by
-@code{cl-flet}. For example,
-
-@example
-(cl-flet ((message (&rest args) (push args saved-msgs)))
- (do-something))
-@end example
-This code attempts to replace the built-in function @code{message}
-with a function that simply saves the messages in a list rather
-than displaying them. The original definition of @code{message}
-will be restored after @code{do-something} exits. This code will
-work fine on messages generated by other Lisp code, but messages
-generated directly inside Emacs will not be caught since they make
-direct C-language calls to the message routines rather than going
-through the Lisp @code{message} function.
+The bindings are lexical in scope. This means that all references to
+the named functions must appear physically within the body of the
+@code{cl-flet} form.
Functions defined by @code{cl-flet} may use the full Common Lisp
argument notation supported by @code{cl-defun}; also, the function
@xref{Program Structure}.
Note that the @file{cl.el} version of this macro behaves slightly
-differently. @xref{Obsolete Macros}.
+differently. In particular, its binding is dynamic rather than
+lexical. @xref{Obsolete Macros}.
@end defmac
@defmac cl-labels (bindings@dots{}) forms@dots{}
are used in macro expansions for temporary variables, to ensure that
their names will not conflict with ``real'' variables in the user's
code.
-@end defun
-@c FIXME texinfo renders this as as cl-gensym-counter in info.
-@c It looks fine in the index, and in the pdf version.
-@defvar cl--gensym-counter
-This variable holds the counter used to generate @code{cl-gensym} names.
-It is incremented after each use by @code{cl-gensym}. In Common Lisp
-this is initialized with 0, but this package initializes it with a
-random (time-dependent) value to avoid trouble when two files that
+(Internally, the variable @code{cl--gensym-counter} holds the counter
+used to generate names. It is incremented after each use. In Common
+Lisp this is initialized with 0, but this package initializes it with
+a random time-dependent value to avoid trouble when two files that
each used @code{cl-gensym} in their compilation are loaded together.
-(Uninterned symbols become interned when the compiler writes them
-out to a file and the Emacs loader loads them, so their names have to
-be treated a bit more carefully than in Common Lisp where uninterned
+Uninterned symbols become interned when the compiler writes them out
+to a file and the Emacs loader loads them, so their names have to be
+treated a bit more carefully than in Common Lisp where uninterned
symbols remain uninterned after loading.)
-@end defvar
+@end defun
@defun cl-gentemp &optional x
This function is like @code{cl-gensym}, except that it produces a new
The @var{state} argument should be a @code{random-state} object
that holds the state of the random number generator. The
function modifies this state object as a side effect. If
-@var{state} is omitted, it defaults to the variable
+@var{state} is omitted, it defaults to the internal variable
@code{cl--random-state}, which contains a pre-initialized
-@code{random-state} object.
+default @code{random-state} object. (Since any number of programs in
+the Emacs process may be accessing @code{cl--random-state} in
+interleaved fashion, the sequence generated from this will be
+irreproducible for all intents and purposes.)
@end defun
-@c FIXME texinfo renders this as cl-random-state in info.
-@c It looks fine in the index, and in the pdf version.
-@defvar cl--random-state
-This variable contains the system ``default'' @code{random-state}
-object, used for calls to @code{cl-random} that do not specify an
-alternative state object. Since any number of programs in the
-Emacs process may be accessing @code{cl--random-state} in interleaved
-fashion, the sequence generated from this variable will be
-irreproducible for all intents and purposes.
-@end defvar
-
@defun cl-make-random-state &optional state
This function creates or copies a @code{random-state} object.
If @var{state} is omitted or @code{nil}, it returns a new copy of
The @code{:key} argument should be passed either @code{nil}, or a
function of one argument. This key function is used as a filter
through which the elements of the sequence are seen; for example,
-@code{(cl-find x y :key 'car)} is similar to @code{(cl-assoc x y)}:
+@code{(cl-find x y :key 'car)} is similar to @code{(cl-assoc x y)}.
It searches for an element of the list whose @sc{car} equals
@code{x}, rather than for an element which equals @code{x} itself.
If @code{:key} is omitted or @code{nil}, the filter is effectively
@code{:test-not} to give a function which returns @emph{false} to
indicate a match. The default test function is @code{eql}.
-Many functions which take @var{item} and @code{:test} or @code{:test-not}
+Many functions that take @var{item} and @code{:test} or @code{:test-not}
arguments also come in @code{-if} and @code{-if-not} varieties,
where a @var{predicate} function is passed instead of @var{item},
and sequence elements match if the predicate returns true on them
to remove all zeros from sequence @code{seq}.
Some operations can work on a subsequence of the argument sequence;
-these function take @code{:start} and @code{:end} arguments which
+these function take @code{:start} and @code{:end} arguments, which
default to zero and the length of the sequence, respectively.
Only elements between @var{start} (inclusive) and @var{end}
(exclusive) are affected by the operation. The @var{end} argument
@defun cl-some predicate seq &rest more-seqs
This function calls @var{predicate} on each element of @var{seq}
in turn; if @var{predicate} returns a non-@code{nil} value,
-@code{some} returns that value, otherwise it returns @code{nil}.
+@code{cl-some} returns that value, otherwise it returns @code{nil}.
Given several sequence arguments, it steps through the sequences
in parallel until the shortest one runs out, just as in
@code{cl-mapcar}. You can rely on the left-to-right order in which
@equiv{} (- 1 (- 2 (- 3 4))) @result{} -2
@end example
-If @code{:key} is specified, it is a function of one argument which
+If @code{:key} is specified, it is a function of one argument, which
is called on each of the sequence elements in turn.
If @code{:initial-value} is specified, it is effectively added to the
If @var{seq1} and @var{seq2} are @code{eq}, then the replacement
will work correctly even if the regions indicated by the start
and end arguments overlap. However, if @var{seq1} and @var{seq2}
-are lists which share storage but are not @code{eq}, and the
+are lists that share storage but are not @code{eq}, and the
start and end arguments specify overlapping regions, the effect
is undefined.
@end defun
@end defun
@defun cl-delete item seq @t{&key :test :test-not :key :count :start :end :from-end}
-This deletes all elements of @var{seq} which match @var{item}.
+This deletes all elements of @var{seq} that match @var{item}.
It is a destructive operation. Since Emacs Lisp does not support
stretchable strings or vectors, this is the same as @code{cl-remove}
for those sequence types. On lists, @code{cl-remove} will copy the
and @code{:key}), the function returns @code{nil}. If there is
a mismatch, the function returns the index (relative to @var{seq1})
of the first mismatching element. This will be the leftmost pair of
-elements which do not match, or the position at which the shorter of
+elements that do not match, or the position at which the shorter of
the two otherwise-matching sequences runs out.
If @code{:from-end} is true, then the elements are compared from right
@defun cl-search seq1 seq2 @t{&key :test :test-not :key :from-end :start1 :end1 :start2 :end2}
This function searches @var{seq2} for a subsequence that matches
@var{seq1} (or part of it specified by @code{:start1} and
-@code{:end1}.) Only matches which fall entirely within the region
+@code{:end1}). Only matches that fall entirely within the region
defined by @code{:start2} and @code{:end2} will be considered.
The return value is the index of the leftmost element of the
leftmost match, relative to the start of @var{seq2}, or @code{nil}
@node Sorting Sequences
@section Sorting Sequences
-@defun clsort seq predicate @t{&key :key}
+@defun cl-sort seq predicate @t{&key :key}
This function sorts @var{seq} into increasing order as determined
by using @var{predicate} to compare pairs of elements. @var{predicate}
should return true (non-@code{nil}) if and only if its first argument
This function differs from Emacs's built-in @code{sort} in that it
can operate on any type of sequence, not just lists. Also, it
-accepts a @code{:key} argument which is used to preprocess data
+accepts a @code{:key} argument, which is used to preprocess data
fed to the @var{predicate} function. For example,
@example
sorts @var{data}, a sequence of strings, into increasing alphabetical
order without regard to case. A @code{:key} function of @code{car}
would be useful for sorting association lists. It should only be a
-simple accessor though, it's used heavily in the current
+simple accessor though, since it's used heavily in the current
implementation.
The @code{cl-sort} function is destructive; it sorts lists by actually
@defun cl-caddr x
This function is equivalent to @code{(car (cdr (cdr @var{x})))}.
-Likewise, this package defines all 28 @code{c@var{xxx}r} functions
+Likewise, this package defines all 24 @code{c@var{xxx}r} functions
where @var{xxx} is up to four @samp{a}s and/or @samp{d}s.
All of these functions are @code{setf}-able, and calls to them
are expanded inline by the byte-compiler for maximum efficiency.
@code{(length @var{x})}, except that if @var{x} is a circular
list (where the @sc{cdr}-chain forms a loop rather than terminating
with @code{nil}), this function returns @code{nil}. (The regular
-@code{length} function would get stuck if given a circular list.)
+@code{length} function would get stuck if given a circular list.
+See also the @code{safe-length} function.)
@end defun
@defun cl-list* arg &rest others
dotted lists like @code{(1 2 . 3)} correctly.
@end defun
-@defun copy-tree x &optional vecp
-This function returns a copy of the tree of cons cells @var{x}.
-@c FIXME? cl-copy-list is not an alias of copy-sequence.
-Unlike @code{copy-sequence} (and its alias @code{cl-copy-list}),
-which copies only along the @sc{cdr} direction, this function
-copies (recursively) along both the @sc{car} and the @sc{cdr}
-directions. If @var{x} is not a cons cell, the function simply
-returns @var{x} unchanged. If the optional @var{vecp} argument
-is true, this function copies vectors (recursively) as well as
-cons cells.
-@end defun
-
@defun cl-tree-equal x y @t{&key :test :test-not :key}
This function compares two trees of cons cells. If @var{x} and
@var{y} are both cons cells, their @sc{car}s and @sc{cdr}s are
@section Lists as Sets
@noindent
-These functions perform operations on lists which represent sets
+These functions perform operations on lists that represent sets
of elements.
@defun cl-member item list @t{&key :test :test-not :key}
The standard Emacs lisp function @code{member} uses @code{equal} for
comparisons; it is equivalent to @code{(cl-member @var{item} @var{list}
-:test 'equal)}.
+:test 'equal)}. With no keyword arguments, @code{cl-member} is
+equivalent to @code{memq}.
@end defun
@findex cl-member-if
@findex cl-member-if-not
The @code{cl-member-if} and @code{cl-member-if-not} functions
-analogously search for elements which satisfy a given predicate.
+analogously search for elements that satisfy a given predicate.
@defun cl-tailp sublist list
This function returns @code{t} if @var{sublist} is a sublist of
@end defun
@defun cl-union list1 list2 @t{&key :test :test-not :key}
-This function combines two lists which represent sets of items,
+This function combines two lists that represent sets of items,
returning a list that represents the union of those two sets.
-The result list will contain all items which appear in @var{list1}
+The resulting list contains all items that appear in @var{list1}
or @var{list2}, and no others. If an item appears in both
-@var{list1} and @var{list2} it will be copied only once. If
+@var{list1} and @var{list2} it is copied only once. If
an item is duplicated in @var{list1} or @var{list2}, it is
undefined whether or not that duplication will survive in the
result list. The order of elements in the result list is also
@defun cl-intersection list1 list2 @t{&key :test :test-not :key}
This function computes the intersection of the sets represented
by @var{list1} and @var{list2}. It returns the list of items
-which appear in both @var{list1} and @var{list2}.
+that appear in both @var{list1} and @var{list2}.
@end defun
@defun cl-nintersection list1 list2 @t{&key :test :test-not :key}
element whose @sc{car} matches (in the sense of @code{:test},
@code{:test-not}, and @code{:key}, or by comparison with @code{eql})
a given @var{item}. It returns the matching element, if any,
-otherwise @code{nil}. It ignores elements of @var{a-list} which
+otherwise @code{nil}. It ignores elements of @var{a-list} that
are not cons cells. (This corresponds to the behavior of
@code{assq} and @code{assoc} in Emacs Lisp; Common Lisp's
@code{assoc} ignores @code{nil}s but considers any other non-cons
@end example
@noindent
-defines a struct type called @code{person} which contains three
+defines a struct type called @code{person} that contains three
slots. Given a @code{person} object @var{p}, you can access those
slots by calling @code{(person-name @var{p})}, @code{(person-age @var{p})},
and @code{(person-sex @var{p})}. You can also change these slots by
-using @code{setf} on any of these place forms:
+using @code{setf} on any of these place forms, for example:
@example
(cl-incf (person-age birthday-boy))
object of the same type whose slots are @code{eq} to those of @var{p}.
Given any Lisp object @var{x}, @code{(person-p @var{x})} returns
-true if @var{x} looks like a @code{person}, false otherwise. (Again,
+true if @var{x} looks like a @code{person}, and false otherwise. (Again,
in Common Lisp this predicate would be exact; in Emacs Lisp the
best it can do is verify that @var{x} is a vector of the correct
-length which starts with the correct tag symbol.)
+length that starts with the correct tag symbol.)
Accessors like @code{person-name} normally check their arguments
(effectively using @code{person-p}) and signal an error if the
symbol followed by any number of @dfn{struct options}; each @var{slot}
is either a slot symbol or a list of the form @samp{(@var{slot-name}
@var{default-value} @var{slot-options}@dots{})}. The @var{default-value}
-is a Lisp form which is evaluated any time an instance of the
+is a Lisp form that is evaluated any time an instance of the
structure type is created without specifying that slot's value.
Common Lisp defines several slot options, but the only one
initialized from the corresponding argument. Slots whose names
do not appear in the argument list are initialized based on the
@var{default-value} in their slot descriptor. Also, @code{&optional}
-and @code{&key} arguments which don't specify defaults take their
+and @code{&key} arguments that don't specify defaults take their
defaults from the slot descriptor. It is valid to include arguments
-which don't correspond to slot names; these are useful if they are
+that don't correspond to slot names; these are useful if they are
referred to in the defaults for optional, keyword, or @code{&aux}
-arguments which @emph{do} correspond to slots.
+arguments that @emph{do} correspond to slots.
You can specify any number of full-format @code{:constructor}
options on a structure. The default constructor is still generated
all copier functions are simply synonyms for @code{copy-sequence}.)
@item :predicate
-The argument is an alternate name for the predicate which recognizes
+The argument is an alternate name for the predicate that recognizes
objects of this type. The default is @code{@var{name}-p}. @code{nil}
means not to generate a predicate function. (If the @code{:type}
option is used without the @code{:named} option, no predicate is
@item :print-function
In full Common Lisp, this option allows you to specify a function
-which is called to print an instance of the structure type. The
+that is called to print an instance of the structure type. The
Emacs Lisp system offers no hooks into the Lisp printer which would
allow for such a feature, so this package simply ignores
@code{:print-function}.
This function takes a single Lisp form as an argument and inserts
a nicely formatted copy of it in the current buffer (which must be
in Lisp mode so that indentation works properly). It also expands
-all Lisp macros which appear in the form. The easiest way to use
+all Lisp macros that appear in the form. The easiest way to use
this function is to go to the @file{*scratch*} buffer and type, say,
@example
@noindent
and type @kbd{C-x C-e} immediately after the closing parenthesis;
-the expansion
+an expansion similar to:
@example
(cl-block nil
If the optional argument @var{full} is true, then @emph{all}
macros are expanded, including @code{cl-block}, @code{cl-eval-when},
and compiler macros. Expansion is done as if @var{form} were
-a top-level form in a file being compiled. For example,
+a top-level form in a file being compiled.
+
+@c FIXME none of these examples are still applicable.
+@ignore
+For example,
@example
(cl-prettyexpand '(cl-pushnew 'x list))
(cl-prettyexpand '(caddr (cl-member 'a list)) t)
@print{} (car (cdr (cdr (memq 'a list))))
@end example
+@end ignore
Note that @code{cl-adjoin}, @code{cl-caddr}, and @code{cl-member} all
have built-in compiler macros to optimize them in common cases.
@end defun
-@ifinfo
-@example
-
-@end example
-@end ifinfo
@appendixsec Error Checking
@noindent
incompatibility.
The Common Lisp standard (as embodied in Steele's book) uses the
-phrase ``it is an error if'' to indicate a situation which is not
+phrase ``it is an error if'' to indicate a situation that is not
supposed to arise in complying programs; implementations are strongly
encouraged but not required to signal an error in these situations.
This package sometimes omits such error checking in the interest of
defined in this package such as @code{cl-find} and @code{cl-member}
do check their keyword arguments for validity.
-@ifinfo
-@example
-
-@end example
-@end ifinfo
-@appendixsec Optimizing Compiler
+@appendixsec Compiler Optimizations
@noindent
-Use of the optimizing Emacs compiler is highly recommended; many of the Common
+Changing the value of @code{byte-optimize} from the default @code{t}
+is highly discouraged; many of the Common
Lisp macros emit
-code which can be improved by optimization. In particular,
+code that can be improved by optimization. In particular,
@code{cl-block}s (whether explicit or implicit in constructs like
@code{cl-defun} and @code{cl-loop}) carry a fair run-time penalty; the
-byte-compiler removes @code{cl-block}s which are not actually
+byte-compiler removes @code{cl-block}s that are not actually
referenced by @code{cl-return} or @code{cl-return-from} inside the block.
@node Common Lisp Compatibility
@appendix Common Lisp Compatibility
@noindent
-Following is a list of all known incompatibilities between this
+The following is a list of all known incompatibilities between this
package and Common Lisp as documented in Steele (2nd edition).
The word @code{cl-defun} is required instead of @code{defun} in order
to use extended Common Lisp argument lists in a function. Likewise,
@code{cl-defmacro} and @code{cl-function} are versions of those forms
which understand full-featured argument lists. The @code{&whole}
-keyword does not work in @code{defmacro} argument lists (except
+keyword does not work in @code{cl-defmacro} argument lists (except
inside recursive argument lists).
The @code{equal} predicate does not distinguish
between IEEE floating-point plus and minus zero. The @code{cl-equalp}
predicate has several differences with Common Lisp; @pxref{Predicates}.
-@c FIXME no longer provided by cl.
-The @code{setf} mechanism is entirely compatible, except that
-setf-methods return a list of five values rather than five
-values directly. Also, the new ``@code{setf} function'' concept
-(typified by @code{(defun (setf foo) @dots{})}) is not implemented.
-
The @code{cl-do-all-symbols} form is the same as @code{cl-do-symbols}
with no @var{obarray} argument. In Common Lisp, this form would
iterate over all symbols in all packages. Since Emacs obarrays
treats them as part of the symbol name. Thus, while @code{mapcar}
and @code{lisp:mapcar} may refer to the same symbol in Common
Lisp, they are totally distinct in Emacs Lisp. Common Lisp
-programs which refer to a symbol by the full name sometimes
+programs that refer to a symbol by the full name sometimes
and the short name other times will not port cleanly to Emacs.
Emacs Lisp does have a concept of ``obarrays'', which are
that @code{flet} affects indirect calls to a function as well as calls
directly inside the @code{flet} form itself.
+This will even work on Emacs primitives, although note that some calls
+to primitive functions internal to Emacs are made without going
+through the symbol's function cell, and so will not be affected by
+@code{flet}. For example,
+
+@example
+(flet ((message (&rest args) (push args saved-msgs)))
+ (do-something))
+@end example
+
+This code attempts to replace the built-in function @code{message}
+with a function that simply saves the messages in a list rather
+than displaying them. The original definition of @code{message}
+will be restored after @code{do-something} exits. This code will
+work fine on messages generated by other Lisp code, but messages
+generated directly inside Emacs will not be caught since they make
+direct C-language calls to the message routines rather than going
+through the Lisp @code{message} function.
+
@c Bug#411.
-Note that many primitives (e.g.@: @code{+}) have special byte-compile
+Note that many primitives (e.g., @code{+}) have special byte-compile
handling. Attempts to redefine such functions using @code{flet} will
fail if byte-compiled.
@c Or cl-flet.
lexical binding that @code{cl-labels} uses.
@end defmac
-@defmac letf (bindings@dots{}) forms@dots{}
-This macro is almost exactly the same as @code{cl-letf}, which
-replaces it (@pxref{Modify Macros}). The only difference is in
-details that relate to some deprecated usage of @code{symbol-function}
-in place forms.
-@end defmac
-
@node Obsolete Setf Customization
@appendixsec Obsolete Ways to Customize Setf
user to extend generalized variables in various ways.
In Emacs, these are obsolete, replaced by various features of
@file{gv.el} in Emacs 24.3.
-@c FIXME details.
+@xref{Adding Generalized Variables,,,elisp,GNU Emacs Lisp Reference Manual}.
+
@defmac define-modify-macro name arglist function [doc-string]
This macro defines a ``read-modify-write'' macro similar to
-@code{cl-incf} and @code{cl-decf}. The macro @var{name} is defined
-to take a @var{place} argument followed by additional arguments
-described by @var{arglist}. The call
+@code{cl-incf} and @code{cl-decf}. You can replace this macro
+with @code{gv-letplace}.
+
+The macro @var{name} is defined to take a @var{place} argument
+followed by additional arguments described by @var{arglist}. The call
@example
(@var{name} @var{place} @var{args}@dots{})
For example:
@example
-(define-modify-macro cl-incf (&optional (n 1)) +)
-(define-modify-macro cl-concatf (&rest args) concat)
+(define-modify-macro incf (&optional (n 1)) +)
+(define-modify-macro concatf (&rest args) concat)
@end example
Note that @code{&key} is not allowed in @var{arglist}, but
Most of the modify macros defined by Common Lisp do not exactly
follow the pattern of @code{define-modify-macro}. For example,
@code{push} takes its arguments in the wrong order, and @code{pop}
-is completely irregular. You can define these macros ``by hand''
-using @code{get-setf-method}, or consult the source
-to see how to use the internal @code{setf} building blocks.
+is completely irregular.
+
+The above @code{incf} example could be written using
+@code{gv-letplace} as:
+@example
+(defmacro incf (place &optional n)
+ (gv-letplace (getter setter) place
+ (macroexp-let2 nil v (or n 1)
+ (funcall setter `(+ ,v ,getter)))))
+@end example
+@ignore
+(defmacro concatf (place &rest args)
+ (gv-letplace (getter setter) place
+ (macroexp-let2 nil v (mapconcat 'identity args "")
+ (funcall setter `(concat ,getter ,v)))))
+@end ignore
@end defmac
@defmac defsetf access-fn update-fn
-This is the simpler of two @code{defsetf} forms. Where
-@var{access-fn} is the name of a function which accesses a place,
-this declares @var{update-fn} to be the corresponding store
-function. From now on,
+This is the simpler of two @code{defsetf} forms, and is
+replaced by @code{gv-define-simple-setter}.
+
+With @var{access-fn} the name of a function that accesses a place,
+this declares @var{update-fn} to be the corresponding store function.
+From now on,
@example
(setf (@var{access-fn} @var{arg1} @var{arg2} @var{arg3}) @var{value})
@noindent
The @var{update-fn} is required to be either a true function, or
-a macro which evaluates its arguments in a function-like way. Also,
+a macro that evaluates its arguments in a function-like way. Also,
the @var{update-fn} is expected to return @var{value} as its result.
Otherwise, the above expansion would not obey the rules for the way
@code{setf} is supposed to behave.
As a special (non-Common-Lisp) extension, a third argument of @code{t}
-to @code{defsetf} says that the @code{update-fn}'s return value is
+to @code{defsetf} says that the return value of @code{update-fn} is
not suitable, so that the above @code{setf} should be expanded to
something more like
temp)
@end example
-Some examples of the use of @code{defsetf}, drawn from the standard
-suite of setf methods, are:
+Some examples are:
@example
(defsetf car setcar)
-(defsetf symbol-value set)
(defsetf buffer-name rename-buffer t)
@end example
+
+These translate directly to @code{gv-define-simple-setter}:
+
+@example
+(gv-define-simple-setter car setcar)
+(gv-define-simple-setter buffer-name rename-buffer t)
+@end example
@end defmac
@defmac defsetf access-fn arglist (store-var) forms@dots{}
-This is the second, more complex, form of @code{defsetf}. It is
-rather like @code{defmacro} except for the additional @var{store-var}
-argument. The @var{forms} should return a Lisp form which stores
-the value of @var{store-var} into the generalized variable formed
-by a call to @var{access-fn} with arguments described by @var{arglist}.
-The @var{forms} may begin with a string which documents the @code{setf}
-method (analogous to the doc string that appears at the front of a
-function).
+This is the second, more complex, form of @code{defsetf}.
+It can be replaced by @code{gv-define-setter}.
+
+This form of @code{defsetf} is rather like @code{defmacro} except for
+the additional @var{store-var} argument. The @var{forms} should
+return a Lisp form that stores the value of @var{store-var} into the
+generalized variable formed by a call to @var{access-fn} with
+arguments described by @var{arglist}. The @var{forms} may begin with
+a string which documents the @code{setf} method (analogous to the doc
+string that appears at the front of a function).
For example, the simple form of @code{defsetf} is shorthand for
The Lisp form that is returned can access the arguments from
@var{arglist} and @var{store-var} in an unrestricted fashion;
-macros like @code{setf} and @code{cl-incf} which invoke this
+macros like @code{cl-incf} that invoke this
setf-method will insert temporary variables as needed to make
sure the apparent order of evaluation is preserved.
-Another example drawn from the standard package:
+Another standard example:
@example
(defsetf nth (n x) (store)
- (list 'setcar (list 'nthcdr n x) store))
+ `(setcar (nthcdr ,n ,x) ,store))
+@end example
+
+You could write this using @code{gv-define-setter} as:
+
+@example
+(gv-define-setter nth (store n x)
+ `(setcar (nthcdr ,n ,x) ,store))
@end example
@end defmac
@defmac define-setf-method access-fn arglist forms@dots{}
-This is the most general way to create new place forms. When
-a @code{setf} to @var{access-fn} with arguments described by
-@var{arglist} is expanded, the @var{forms} are evaluated and
-must return a list of five items:
+This is the most general way to create new place forms. You can
+replace this by @code{gv-define-setter} or @code{gv-define-expander}.
+
+When a @code{setf} to @var{access-fn} with arguments described by
+@var{arglist} is expanded, the @var{forms} are evaluated and must
+return a list of five items:
@enumerate
@item
from a call to @code{gensym}).
@item
-A Lisp form which stores the contents of the store variable into
+A Lisp form that stores the contents of the store variable into
the generalized variable, assuming the temporaries have been
bound as described above.
@item
-A Lisp form which accesses the contents of the generalized variable,
+A Lisp form that accesses the contents of the generalized variable,
assuming the temporaries have been bound.
@end enumerate
except that the method returns a list of five values rather
than the five values themselves, since Emacs Lisp does not
support Common Lisp's notion of multiple return values.
+(Note that the @code{setf} implementation provided by @file{gv.el}
+does not use this five item format. Its use here is only for
+backwards compatibility.)
Once again, the @var{forms} may begin with a documentation string.
@code{defsetf}, the second return value is simply the list of
arguments in the place form, and the first return value is a
list of a corresponding number of temporary variables generated
-by @code{cl-gensym}. Macros like @code{setf} and @code{cl-incf} which
+@c FIXME I don't think this is true anymore.
+by @code{cl-gensym}. Macros like @code{cl-incf} that
use this setf-method will optimize away most temporaries that
turn out to be unnecessary, so there is little reason for the
setf-method itself to optimize.
@end defmac
+@c Removed in Emacs 24.3, not possible to make a compatible replacement.
+@ignore
@defun get-setf-method place &optional env
This function returns the setf-method for @var{place}, by
invoking the definition previously recorded by @code{defsetf}
or @code{define-setf-method}. The result is a list of five
values as described above. You can use this function to build
-your own @code{cl-incf}-like modify macros. (Actually, it is
-@c FIXME?
-better to use the internal functions @code{cl-setf-do-modify}
-and @code{cl-setf-do-store}, which are a bit easier to use and
-which also do a number of optimizations; consult the source
-code for the @code{cl-incf} function for a simple example.)
+your own @code{cl-incf}-like modify macros.
The argument @var{env} specifies the ``environment'' to be
passed on to @code{macroexpand} if @code{get-setf-method} should
need to expand a macro in @var{place}. It should come from
an @code{&environment} argument to the macro or setf-method
that called @code{get-setf-method}.
-
-See also the source code for the setf-method for
-@c Also @code{apply}, but that is commented out.
-@code{substring}, which works by calling @code{get-setf-method} on a
-simpler case, then massaging the result.
@end defun
-
-Modern Common Lisp defines a second, independent way to specify
-the @code{setf} behavior of a function, namely ``@code{setf}
-functions'' whose names are lists @code{(setf @var{name})}
-rather than symbols. For example, @code{(defun (setf foo) @dots{})}
-defines the function that is used when @code{setf} is applied to
-@code{foo}. This package does not currently support @code{setf}
-functions. In particular, it is a compile-time error to use
-@code{setf} on a form which has not already been @code{defsetf}'d
-or otherwise declared; in newer Common Lisps, this would not be
-an error since the function @code{(setf @var{func})} might be
-defined later.
+@end ignore
@node GNU Free Documentation License