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date Mon, 13 Aug 2007 11:36:19 +0200
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1 @c -*-texinfo-*- 1 @c -*-texinfo-*-
2 @c This is part of the XEmacs Lisp Reference Manual. 2 @c This is part of the XEmacs Lisp Reference Manual.
3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. 3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
4 @c See the file lispref.texi for copying conditions. 4 @c See the file lispref.texi for copying conditions.
5 @setfilename ../../info/functions.info 5 @setfilename ../../info/functions.info
6 @node Functions, Macros, Variables, Top 6 @node Functions, Macros, Variables, Top
7 @chapter Functions 7 @chapter Functions
8 8
15 * Lambda Expressions:: How functions are expressed as Lisp objects. 15 * Lambda Expressions:: How functions are expressed as Lisp objects.
16 * Function Names:: A symbol can serve as the name of a function. 16 * Function Names:: A symbol can serve as the name of a function.
17 * Defining Functions:: Lisp expressions for defining functions. 17 * Defining Functions:: Lisp expressions for defining functions.
18 * Calling Functions:: How to use an existing function. 18 * Calling Functions:: How to use an existing function.
19 * Mapping Functions:: Applying a function to each element of a list, etc. 19 * Mapping Functions:: Applying a function to each element of a list, etc.
20 * Anonymous Functions:: Lambda expressions are functions with no names. 20 * Anonymous Functions:: Lambda expressions are functions with no names.
21 * Function Cells:: Accessing or setting the function definition 21 * Function Cells:: Accessing or setting the function definition
22 of a symbol. 22 of a symbol.
23 * Inline Functions:: Defining functions that the compiler will open code. 23 * Inline Functions:: Defining functions that the compiler will open code.
24 * Related Topics:: Cross-references to specific Lisp primitives 24 * Related Topics:: Cross-references to specific Lisp primitives
25 that have a special bearing on how functions work. 25 that have a special bearing on how functions work.
669 669
670 @defun identity arg 670 @defun identity arg
671 This function returns @var{arg} and has no side effects. 671 This function returns @var{arg} and has no side effects.
672 @end defun 672 @end defun
673 673
674 @defun ignore &rest args 674 @deffn Command ignore &rest args
675 This function ignores any arguments and returns @code{nil}. 675 This function ignores any arguments and returns @code{nil}.
676 @end defun 676 @end deffn
677 677
678 @node Mapping Functions 678 @node Mapping Functions
679 @section Mapping Functions 679 @section Mapping Functions
680 @cindex mapping functions 680 @cindex mapping functions
681 681
716 @group 716 @group
717 (defun mapcar* (f &rest args) 717 (defun mapcar* (f &rest args)
718 "Apply FUNCTION to successive cars of all ARGS. 718 "Apply FUNCTION to successive cars of all ARGS.
719 Return the list of results." 719 Return the list of results."
720 ;; @r{If no list is exhausted,} 720 ;; @r{If no list is exhausted,}
721 (if (not (memq 'nil args)) 721 (if (not (memq 'nil args))
722 ;; @r{apply function to @sc{car}s.} 722 ;; @r{apply function to @sc{car}s.}
723 (cons (apply f (mapcar 'car args)) 723 (cons (apply f (mapcar 'car args))
724 (apply 'mapcar* f 724 (apply 'mapcar* f
725 ;; @r{Recurse for rest of elements.} 725 ;; @r{Recurse for rest of elements.}
726 (mapcar 'cdr args))))) 726 (mapcar 'cdr args)))))
727 @end group 727 @end group
728 728
729 @group 729 @group
741 other suitable punctuation. 741 other suitable punctuation.
742 742
743 The argument @var{function} must be a function that can take one 743 The argument @var{function} must be a function that can take one
744 argument and return a string. The argument @var{sequence} can be any 744 argument and return a string. The argument @var{sequence} can be any
745 kind of sequence; that is, a list, a vector, a bit vector, or a string. 745 kind of sequence; that is, a list, a vector, a bit vector, or a string.
746 746
747 @smallexample 747 @smallexample
748 @group 748 @group
749 (mapconcat 'symbol-name 749 (mapconcat 'symbol-name
750 '(The cat in the hat) 750 '(The cat in the hat)
751 " ") 751 " ")
929 You can test the voidness of a symbol's function definition with 929 You can test the voidness of a symbol's function definition with
930 @code{fboundp}. After you have given a symbol a function definition, you 930 @code{fboundp}. After you have given a symbol a function definition, you
931 can make it void once more using @code{fmakunbound}. 931 can make it void once more using @code{fmakunbound}.
932 932
933 @defun fboundp symbol 933 @defun fboundp symbol
934 This function returns @code{t} if the symbol has an object in its 934 This function returns @code{t} if @var{symbol} has an object in its
935 function cell, @code{nil} otherwise. It does not check that the object 935 function cell, @code{nil} otherwise. It does not check that the object
936 is a legitimate function. 936 is a legitimate function.
937 @end defun 937 @end defun
938 938
939 @defun fmakunbound symbol 939 @defun fmakunbound symbol
974 making an alternate name for a function.) 974 making an alternate name for a function.)
975 975
976 @item 976 @item
977 Giving a symbol a function definition that is not a list and therefore 977 Giving a symbol a function definition that is not a list and therefore
978 cannot be made with @code{defun}. For example, you can use @code{fset} 978 cannot be made with @code{defun}. For example, you can use @code{fset}
979 to give a symbol @code{s1} a function definition which is another symbol 979 to give a symbol @var{symbol1} a function definition which is another symbol
980 @code{s2}; then @code{s1} serves as an alias for whatever definition 980 @var{symbol2}; then @var{symbol1} serves as an alias for whatever definition
981 @code{s2} presently has. 981 @var{symbol2} presently has.
982 982
983 @item 983 @item
984 In constructs for defining or altering functions. If @code{defun} 984 In constructs for defining or altering functions. If @code{defun}
985 were not a primitive, it could be written in Lisp (as a macro) using 985 were not a primitive, it could be written in Lisp (as a macro) using
986 @code{fset}. 986 @code{fset}.