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1 @c -*-texinfo-*-
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2 @c This is part of the XEmacs Lisp Reference Manual.
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3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
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4 @c See the file lispref.texi for copying conditions.
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5 @setfilename ../../info/functions.info
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6 @node Functions, Macros, Variables, Top
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7 @chapter Functions
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8
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9 A Lisp program is composed mainly of Lisp functions. This chapter
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10 explains what functions are, how they accept arguments, and how to
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11 define them.
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12
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13 @menu
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14 * What Is a Function:: Lisp functions vs. primitives; terminology.
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15 * Lambda Expressions:: How functions are expressed as Lisp objects.
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16 * Function Names:: A symbol can serve as the name of a function.
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17 * Defining Functions:: Lisp expressions for defining functions.
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18 * Calling Functions:: How to use an existing function.
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19 * Mapping Functions:: Applying a function to each element of a list, etc.
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20 * Anonymous Functions:: Lambda expressions are functions with no names.
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21 * Function Cells:: Accessing or setting the function definition
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22 of a symbol.
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23 * Inline Functions:: Defining functions that the compiler will open code.
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24 * Related Topics:: Cross-references to specific Lisp primitives
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25 that have a special bearing on how functions work.
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26 @end menu
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27
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28 @node What Is a Function
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29 @section What Is a Function?
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30
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31 In a general sense, a function is a rule for carrying on a computation
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32 given several values called @dfn{arguments}. The result of the
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33 computation is called the value of the function. The computation can
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34 also have side effects: lasting changes in the values of variables or
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35 the contents of data structures.
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36
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37 Here are important terms for functions in XEmacs Lisp and for other
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38 function-like objects.
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39
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40 @table @dfn
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41 @item function
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42 @cindex function
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43 In XEmacs Lisp, a @dfn{function} is anything that can be applied to
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44 arguments in a Lisp program. In some cases, we use it more
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45 specifically to mean a function written in Lisp. Special forms and
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46 macros are not functions.
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47
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48 @item primitive
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49 @cindex primitive
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50 @cindex subr
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51 @cindex built-in function
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52 A @dfn{primitive} is a function callable from Lisp that is written in C,
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53 such as @code{car} or @code{append}. These functions are also called
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54 @dfn{built-in} functions or @dfn{subrs}. (Special forms are also
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55 considered primitives.)
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56
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57 Usually the reason that a function is a primitives is because it is
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58 fundamental, because it provides a low-level interface to operating
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59 system services, or because it needs to run fast. Primitives can be
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60 modified or added only by changing the C sources and recompiling the
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61 editor. See @ref{Writing Lisp Primitives,,, internals, XEmacs
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62 Internals Manual}.
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63
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64 @item lambda expression
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65 A @dfn{lambda expression} is a function written in Lisp.
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66 These are described in the following section.
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67 @ifinfo
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68 @xref{Lambda Expressions}.
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69 @end ifinfo
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70
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71 @item special form
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72 A @dfn{special form} is a primitive that is like a function but does not
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73 evaluate all of its arguments in the usual way. It may evaluate only
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74 some of the arguments, or may evaluate them in an unusual order, or
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75 several times. Many special forms are described in @ref{Control
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76 Structures}.
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77
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78 @item macro
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79 @cindex macro
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80 A @dfn{macro} is a construct defined in Lisp by the programmer. It
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81 differs from a function in that it translates a Lisp expression that you
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82 write into an equivalent expression to be evaluated instead of the
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83 original expression. Macros enable Lisp programmers to do the sorts of
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84 things that special forms can do. @xref{Macros}, for how to define and
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85 use macros.
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86
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87 @item command
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88 @cindex command
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89 A @dfn{command} is an object that @code{command-execute} can invoke; it
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90 is a possible definition for a key sequence. Some functions are
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91 commands; a function written in Lisp is a command if it contains an
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92 interactive declaration (@pxref{Defining Commands}). Such a function
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93 can be called from Lisp expressions like other functions; in this case,
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94 the fact that the function is a command makes no difference.
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95
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96 Keyboard macros (strings and vectors) are commands also, even though
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97 they are not functions. A symbol is a command if its function
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98 definition is a command; such symbols can be invoked with @kbd{M-x}.
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99 The symbol is a function as well if the definition is a function.
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100 @xref{Command Overview}.
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101
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102 @item keystroke command
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103 @cindex keystroke command
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104 A @dfn{keystroke command} is a command that is bound to a key sequence
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105 (typically one to three keystrokes). The distinction is made here
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106 merely to avoid confusion with the meaning of ``command'' in non-Emacs
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107 editors; for Lisp programs, the distinction is normally unimportant.
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108
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109 @item compiled function
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110 A @dfn{compiled function} is a function that has been compiled by the
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111 byte compiler. @xref{Compiled-Function Type}.
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112 @end table
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113
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114 @defun subrp object
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115 This function returns @code{t} if @var{object} is a built-in function
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116 (i.e., a Lisp primitive).
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117
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118 @example
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119 @group
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120 (subrp 'message) ; @r{@code{message} is a symbol,}
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121 @result{} nil ; @r{not a subr object.}
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122 @end group
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123 @group
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124 (subrp (symbol-function 'message))
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125 @result{} t
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126 @end group
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127 @end example
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128 @end defun
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129
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130 @defun compiled-function-p object
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131 This function returns @code{t} if @var{object} is a compiled
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132 function. For example:
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133
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134 @example
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135 @group
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136 (compiled-function-p (symbol-function 'next-line))
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137 @result{} t
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138 @end group
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139 @end example
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140 @end defun
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141
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142 @node Lambda Expressions
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143 @section Lambda Expressions
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144 @cindex lambda expression
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145
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146 A function written in Lisp is a list that looks like this:
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147
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148 @example
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149 (lambda (@var{arg-variables}@dots{})
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150 @r{[}@var{documentation-string}@r{]}
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151 @r{[}@var{interactive-declaration}@r{]}
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152 @var{body-forms}@dots{})
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153 @end example
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154
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155 @noindent
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156 Such a list is called a @dfn{lambda expression}. In XEmacs Lisp, it
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157 actually is valid as an expression---it evaluates to itself. In some
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158 other Lisp dialects, a lambda expression is not a valid expression at
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159 all. In either case, its main use is not to be evaluated as an
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160 expression, but to be called as a function.
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161
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162 @menu
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163 * Lambda Components:: The parts of a lambda expression.
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164 * Simple Lambda:: A simple example.
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165 * Argument List:: Details and special features of argument lists.
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166 * Function Documentation:: How to put documentation in a function.
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167 @end menu
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168
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169 @node Lambda Components
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170 @subsection Components of a Lambda Expression
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171
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172 @ifinfo
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173
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174 A function written in Lisp (a ``lambda expression'') is a list that
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175 looks like this:
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176
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177 @example
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178 (lambda (@var{arg-variables}@dots{})
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179 [@var{documentation-string}]
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180 [@var{interactive-declaration}]
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181 @var{body-forms}@dots{})
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182 @end example
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183 @end ifinfo
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184
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185 @cindex lambda list
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186 The first element of a lambda expression is always the symbol
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187 @code{lambda}. This indicates that the list represents a function. The
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188 reason functions are defined to start with @code{lambda} is so that
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189 other lists, intended for other uses, will not accidentally be valid as
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190 functions.
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191
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192 The second element is a list of symbols--the argument variable names.
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193 This is called the @dfn{lambda list}. When a Lisp function is called,
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194 the argument values are matched up against the variables in the lambda
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195 list, which are given local bindings with the values provided.
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196 @xref{Local Variables}.
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197
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198 The documentation string is a Lisp string object placed within the
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199 function definition to describe the function for the XEmacs help
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200 facilities. @xref{Function Documentation}.
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201
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202 The interactive declaration is a list of the form @code{(interactive
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203 @var{code-string})}. This declares how to provide arguments if the
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204 function is used interactively. Functions with this declaration are called
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205 @dfn{commands}; they can be called using @kbd{M-x} or bound to a key.
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206 Functions not intended to be called in this way should not have interactive
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207 declarations. @xref{Defining Commands}, for how to write an interactive
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208 declaration.
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209
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210 @cindex body of function
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211 The rest of the elements are the @dfn{body} of the function: the Lisp
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212 code to do the work of the function (or, as a Lisp programmer would say,
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213 ``a list of Lisp forms to evaluate''). The value returned by the
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214 function is the value returned by the last element of the body.
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215
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216 @node Simple Lambda
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217 @subsection A Simple Lambda-Expression Example
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218
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219 Consider for example the following function:
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220
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221 @example
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222 (lambda (a b c) (+ a b c))
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223 @end example
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224
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225 @noindent
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226 We can call this function by writing it as the @sc{car} of an
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227 expression, like this:
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228
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229 @example
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230 @group
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231 ((lambda (a b c) (+ a b c))
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232 1 2 3)
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233 @end group
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234 @end example
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235
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236 @noindent
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237 This call evaluates the body of the lambda expression with the variable
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238 @code{a} bound to 1, @code{b} bound to 2, and @code{c} bound to 3.
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239 Evaluation of the body adds these three numbers, producing the result 6;
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240 therefore, this call to the function returns the value 6.
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241
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242 Note that the arguments can be the results of other function calls, as in
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243 this example:
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244
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245 @example
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246 @group
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247 ((lambda (a b c) (+ a b c))
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248 1 (* 2 3) (- 5 4))
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249 @end group
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250 @end example
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251
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252 @noindent
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253 This evaluates the arguments @code{1}, @code{(* 2 3)}, and @code{(- 5
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254 4)} from left to right. Then it applies the lambda expression to the
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255 argument values 1, 6 and 1 to produce the value 8.
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256
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257 It is not often useful to write a lambda expression as the @sc{car} of
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258 a form in this way. You can get the same result, of making local
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259 variables and giving them values, using the special form @code{let}
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260 (@pxref{Local Variables}). And @code{let} is clearer and easier to use.
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261 In practice, lambda expressions are either stored as the function
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262 definitions of symbols, to produce named functions, or passed as
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263 arguments to other functions (@pxref{Anonymous Functions}).
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264
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265 However, calls to explicit lambda expressions were very useful in the
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266 old days of Lisp, before the special form @code{let} was invented. At
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267 that time, they were the only way to bind and initialize local
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268 variables.
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269
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270 @node Argument List
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271 @subsection Advanced Features of Argument Lists
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272 @kindex wrong-number-of-arguments
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273 @cindex argument binding
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274 @cindex binding arguments
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275
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276 Our simple sample function, @code{(lambda (a b c) (+ a b c))},
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277 specifies three argument variables, so it must be called with three
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278 arguments: if you try to call it with only two arguments or four
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279 arguments, you get a @code{wrong-number-of-arguments} error.
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280
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281 It is often convenient to write a function that allows certain
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282 arguments to be omitted. For example, the function @code{substring}
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283 accepts three arguments---a string, the start index and the end
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284 index---but the third argument defaults to the @var{length} of the
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285 string if you omit it. It is also convenient for certain functions to
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286 accept an indefinite number of arguments, as the functions @code{list}
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287 and @code{+} do.
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288
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289 @cindex optional arguments
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290 @cindex rest arguments
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291 @kindex &optional
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292 @kindex &rest
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293 To specify optional arguments that may be omitted when a function
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294 is called, simply include the keyword @code{&optional} before the optional
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295 arguments. To specify a list of zero or more extra arguments, include the
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296 keyword @code{&rest} before one final argument.
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297
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298 Thus, the complete syntax for an argument list is as follows:
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299
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300 @example
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301 @group
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302 (@var{required-vars}@dots{}
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303 @r{[}&optional @var{optional-vars}@dots{}@r{]}
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304 @r{[}&rest @var{rest-var}@r{]})
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305 @end group
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306 @end example
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307
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308 @noindent
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309 The square brackets indicate that the @code{&optional} and @code{&rest}
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310 clauses, and the variables that follow them, are optional.
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311
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312 A call to the function requires one actual argument for each of the
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313 @var{required-vars}. There may be actual arguments for zero or more of
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314 the @var{optional-vars}, and there cannot be any actual arguments beyond
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315 that unless the lambda list uses @code{&rest}. In that case, there may
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316 be any number of extra actual arguments.
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317
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318 If actual arguments for the optional and rest variables are omitted,
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319 then they always default to @code{nil}. There is no way for the
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320 function to distinguish between an explicit argument of @code{nil} and
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321 an omitted argument. However, the body of the function is free to
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322 consider @code{nil} an abbreviation for some other meaningful value.
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323 This is what @code{substring} does; @code{nil} as the third argument to
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324 @code{substring} means to use the length of the string supplied.
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325
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326 @cindex CL note---default optional arg
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327 @quotation
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328 @b{Common Lisp note:} Common Lisp allows the function to specify what
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329 default value to use when an optional argument is omitted; XEmacs Lisp
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330 always uses @code{nil}.
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331 @end quotation
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332
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333 For example, an argument list that looks like this:
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334
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335 @example
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336 (a b &optional c d &rest e)
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337 @end example
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338
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339 @noindent
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340 binds @code{a} and @code{b} to the first two actual arguments, which are
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341 required. If one or two more arguments are provided, @code{c} and
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342 @code{d} are bound to them respectively; any arguments after the first
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343 four are collected into a list and @code{e} is bound to that list. If
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344 there are only two arguments, @code{c} is @code{nil}; if two or three
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345 arguments, @code{d} is @code{nil}; if four arguments or fewer, @code{e}
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346 is @code{nil}.
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347
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348 There is no way to have required arguments following optional
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349 ones---it would not make sense. To see why this must be so, suppose
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350 that @code{c} in the example were optional and @code{d} were required.
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351 Suppose three actual arguments are given; which variable would the third
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352 argument be for? Similarly, it makes no sense to have any more
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353 arguments (either required or optional) after a @code{&rest} argument.
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354
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355 Here are some examples of argument lists and proper calls:
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356
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357 @smallexample
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358 ((lambda (n) (1+ n)) ; @r{One required:}
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359 1) ; @r{requires exactly one argument.}
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360 @result{} 2
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361 ((lambda (n &optional n1) ; @r{One required and one optional:}
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362 (if n1 (+ n n1) (1+ n))) ; @r{1 or 2 arguments.}
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363 1 2)
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364 @result{} 3
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365 ((lambda (n &rest ns) ; @r{One required and one rest:}
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366 (+ n (apply '+ ns))) ; @r{1 or more arguments.}
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367 1 2 3 4 5)
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368 @result{} 15
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369 @end smallexample
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370
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371 @node Function Documentation
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372 @subsection Documentation Strings of Functions
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373 @cindex documentation of function
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374
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375 A lambda expression may optionally have a @dfn{documentation string} just
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376 after the lambda list. This string does not affect execution of the
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377 function; it is a kind of comment, but a systematized comment which
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378 actually appears inside the Lisp world and can be used by the XEmacs help
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379 facilities. @xref{Documentation}, for how the @var{documentation-string} is
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380 accessed.
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381
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382 It is a good idea to provide documentation strings for all the
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383 functions in your program, even those that are only called from within
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384 your program. Documentation strings are like comments, except that they
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385 are easier to access.
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386
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387 The first line of the documentation string should stand on its own,
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388 because @code{apropos} displays just this first line. It should consist
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389 of one or two complete sentences that summarize the function's purpose.
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390
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391 The start of the documentation string is usually indented in the source file,
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392 but since these spaces come before the starting double-quote, they are not part of
|
|
|
393 the string. Some people make a practice of indenting any additional
|
|
|
394 lines of the string so that the text lines up in the program source.
|
|
|
395 @emph{This is a mistake.} The indentation of the following lines is
|
|
|
396 inside the string; what looks nice in the source code will look ugly
|
|
|
397 when displayed by the help commands.
|
|
|
398
|
|
|
399 You may wonder how the documentation string could be optional, since
|
|
|
400 there are required components of the function that follow it (the body).
|
|
|
401 Since evaluation of a string returns that string, without any side effects,
|
|
|
402 it has no effect if it is not the last form in the body. Thus, in
|
|
|
403 practice, there is no confusion between the first form of the body and the
|
|
|
404 documentation string; if the only body form is a string then it serves both
|
|
|
405 as the return value and as the documentation.
|
|
|
406
|
|
|
407 @node Function Names
|
|
|
408 @section Naming a Function
|
|
|
409 @cindex function definition
|
|
|
410 @cindex named function
|
|
|
411 @cindex function name
|
|
|
412
|
|
|
413 In most computer languages, every function has a name; the idea of a
|
|
|
414 function without a name is nonsensical. In Lisp, a function in the
|
|
|
415 strictest sense has no name. It is simply a list whose first element is
|
|
|
416 @code{lambda}, or a primitive subr-object.
|
|
|
417
|
|
|
418 However, a symbol can serve as the name of a function. This happens
|
|
|
419 when you put the function in the symbol's @dfn{function cell}
|
|
|
420 (@pxref{Symbol Components}). Then the symbol itself becomes a valid,
|
|
|
421 callable function, equivalent to the list or subr-object that its
|
|
|
422 function cell refers to. The contents of the function cell are also
|
|
|
423 called the symbol's @dfn{function definition}. The procedure of using a
|
|
|
424 symbol's function definition in place of the symbol is called
|
|
|
425 @dfn{symbol function indirection}; see @ref{Function Indirection}.
|
|
|
426
|
|
|
427 In practice, nearly all functions are given names in this way and
|
|
|
428 referred to through their names. For example, the symbol @code{car} works
|
|
|
429 as a function and does what it does because the primitive subr-object
|
|
|
430 @code{#<subr car>} is stored in its function cell.
|
|
|
431
|
|
|
432 We give functions names because it is convenient to refer to them by
|
|
|
433 their names in Lisp expressions. For primitive subr-objects such as
|
|
|
434 @code{#<subr car>}, names are the only way you can refer to them: there
|
|
|
435 is no read syntax for such objects. For functions written in Lisp, the
|
|
|
436 name is more convenient to use in a call than an explicit lambda
|
|
|
437 expression. Also, a function with a name can refer to itself---it can
|
|
|
438 be recursive. Writing the function's name in its own definition is much
|
|
|
439 more convenient than making the function definition point to itself
|
|
|
440 (something that is not impossible but that has various disadvantages in
|
|
|
441 practice).
|
|
|
442
|
|
|
443 We often identify functions with the symbols used to name them. For
|
|
|
444 example, we often speak of ``the function @code{car}'', not
|
|
|
445 distinguishing between the symbol @code{car} and the primitive
|
|
|
446 subr-object that is its function definition. For most purposes, there
|
|
|
447 is no need to distinguish.
|
|
|
448
|
|
|
449 Even so, keep in mind that a function need not have a unique name. While
|
|
|
450 a given function object @emph{usually} appears in the function cell of only
|
|
|
451 one symbol, this is just a matter of convenience. It is easy to store
|
|
|
452 it in several symbols using @code{fset}; then each of the symbols is
|
|
|
453 equally well a name for the same function.
|
|
|
454
|
|
|
455 A symbol used as a function name may also be used as a variable;
|
|
|
456 these two uses of a symbol are independent and do not conflict.
|
|
|
457
|
|
|
458 @node Defining Functions
|
|
|
459 @section Defining Functions
|
|
|
460 @cindex defining a function
|
|
|
461
|
|
|
462 We usually give a name to a function when it is first created. This
|
|
|
463 is called @dfn{defining a function}, and it is done with the
|
|
|
464 @code{defun} special form.
|
|
|
465
|
|
|
466 @defspec defun name argument-list body-forms
|
|
|
467 @code{defun} is the usual way to define new Lisp functions. It
|
|
|
468 defines the symbol @var{name} as a function that looks like this:
|
|
|
469
|
|
|
470 @example
|
|
|
471 (lambda @var{argument-list} . @var{body-forms})
|
|
|
472 @end example
|
|
|
473
|
|
|
474 @code{defun} stores this lambda expression in the function cell of
|
|
|
475 @var{name}. It returns the value @var{name}, but usually we ignore this
|
|
|
476 value.
|
|
|
477
|
|
|
478 As described previously (@pxref{Lambda Expressions}),
|
|
|
479 @var{argument-list} is a list of argument names and may include the
|
|
|
480 keywords @code{&optional} and @code{&rest}. Also, the first two forms
|
|
|
481 in @var{body-forms} may be a documentation string and an interactive
|
|
|
482 declaration.
|
|
|
483
|
|
|
484 There is no conflict if the same symbol @var{name} is also used as a
|
|
|
485 variable, since the symbol's value cell is independent of the function
|
|
|
486 cell. @xref{Symbol Components}.
|
|
|
487
|
|
|
488 Here are some examples:
|
|
|
489
|
|
|
490 @example
|
|
|
491 @group
|
|
|
492 (defun foo () 5)
|
|
|
493 @result{} foo
|
|
|
494 @end group
|
|
|
495 @group
|
|
|
496 (foo)
|
|
|
497 @result{} 5
|
|
|
498 @end group
|
|
|
499
|
|
|
500 @group
|
|
|
501 (defun bar (a &optional b &rest c)
|
|
|
502 (list a b c))
|
|
|
503 @result{} bar
|
|
|
504 @end group
|
|
|
505 @group
|
|
|
506 (bar 1 2 3 4 5)
|
|
|
507 @result{} (1 2 (3 4 5))
|
|
|
508 @end group
|
|
|
509 @group
|
|
|
510 (bar 1)
|
|
|
511 @result{} (1 nil nil)
|
|
|
512 @end group
|
|
|
513 @group
|
|
|
514 (bar)
|
|
|
515 @error{} Wrong number of arguments.
|
|
|
516 @end group
|
|
|
517
|
|
|
518 @group
|
|
|
519 (defun capitalize-backwards ()
|
|
|
520 "Upcase the last letter of a word."
|
|
|
521 (interactive)
|
|
|
522 (backward-word 1)
|
|
|
523 (forward-word 1)
|
|
|
524 (backward-char 1)
|
|
|
525 (capitalize-word 1))
|
|
|
526 @result{} capitalize-backwards
|
|
|
527 @end group
|
|
|
528 @end example
|
|
|
529
|
|
|
530 Be careful not to redefine existing functions unintentionally.
|
|
|
531 @code{defun} redefines even primitive functions such as @code{car}
|
|
|
532 without any hesitation or notification. Redefining a function already
|
|
|
533 defined is often done deliberately, and there is no way to distinguish
|
|
|
534 deliberate redefinition from unintentional redefinition.
|
|
|
535 @end defspec
|
|
|
536
|
|
|
537 @defun define-function name definition
|
|
|
538 @defunx defalias name definition
|
|
|
539 These equivalent special forms define the symbol @var{name} as a
|
|
|
540 function, with definition @var{definition} (which can be any valid Lisp
|
|
|
541 function).
|
|
|
542
|
|
|
543 The proper place to use @code{define-function} or @code{defalias} is
|
|
|
544 where a specific function name is being defined---especially where that
|
|
|
545 name appears explicitly in the source file being loaded. This is
|
|
|
546 because @code{define-function} and @code{defalias} record which file
|
|
|
547 defined the function, just like @code{defun}.
|
|
|
548 (@pxref{Unloading}).
|
|
|
549
|
|
|
550 By contrast, in programs that manipulate function definitions for other
|
|
|
551 purposes, it is better to use @code{fset}, which does not keep such
|
|
|
552 records.
|
|
|
553 @end defun
|
|
|
554
|
|
|
555 See also @code{defsubst}, which defines a function like @code{defun}
|
|
|
556 and tells the Lisp compiler to open-code it. @xref{Inline Functions}.
|
|
|
557
|
|
|
558 @node Calling Functions
|
|
|
559 @section Calling Functions
|
|
|
560 @cindex function invocation
|
|
|
561 @cindex calling a function
|
|
|
562
|
|
|
563 Defining functions is only half the battle. Functions don't do
|
|
|
564 anything until you @dfn{call} them, i.e., tell them to run. Calling a
|
|
|
565 function is also known as @dfn{invocation}.
|
|
|
566
|
|
|
567 The most common way of invoking a function is by evaluating a list.
|
|
|
568 For example, evaluating the list @code{(concat "a" "b")} calls the
|
|
|
569 function @code{concat} with arguments @code{"a"} and @code{"b"}.
|
|
|
570 @xref{Evaluation}, for a description of evaluation.
|
|
|
571
|
|
|
572 When you write a list as an expression in your program, the function
|
|
|
573 name is part of the program. This means that you choose which function
|
|
|
574 to call, and how many arguments to give it, when you write the program.
|
|
|
575 Usually that's just what you want. Occasionally you need to decide at
|
|
|
576 run time which function to call. To do that, use the functions
|
|
|
577 @code{funcall} and @code{apply}.
|
|
|
578
|
|
|
579 @defun funcall function &rest arguments
|
|
|
580 @code{funcall} calls @var{function} with @var{arguments}, and returns
|
|
|
581 whatever @var{function} returns.
|
|
|
582
|
|
|
583 Since @code{funcall} is a function, all of its arguments, including
|
|
|
584 @var{function}, are evaluated before @code{funcall} is called. This
|
|
|
585 means that you can use any expression to obtain the function to be
|
|
|
586 called. It also means that @code{funcall} does not see the expressions
|
|
|
587 you write for the @var{arguments}, only their values. These values are
|
|
|
588 @emph{not} evaluated a second time in the act of calling @var{function};
|
|
|
589 @code{funcall} enters the normal procedure for calling a function at the
|
|
|
590 place where the arguments have already been evaluated.
|
|
|
591
|
|
|
592 The argument @var{function} must be either a Lisp function or a
|
|
|
593 primitive function. Special forms and macros are not allowed, because
|
|
|
594 they make sense only when given the ``unevaluated'' argument
|
|
|
595 expressions. @code{funcall} cannot provide these because, as we saw
|
|
|
596 above, it never knows them in the first place.
|
|
|
597
|
|
|
598 @example
|
|
|
599 @group
|
|
|
600 (setq f 'list)
|
|
|
601 @result{} list
|
|
|
602 @end group
|
|
|
603 @group
|
|
|
604 (funcall f 'x 'y 'z)
|
|
|
605 @result{} (x y z)
|
|
|
606 @end group
|
|
|
607 @group
|
|
|
608 (funcall f 'x 'y '(z))
|
|
|
609 @result{} (x y (z))
|
|
|
610 @end group
|
|
|
611 @group
|
|
|
612 (funcall 'and t nil)
|
|
|
613 @error{} Invalid function: #<subr and>
|
|
|
614 @end group
|
|
|
615 @end example
|
|
|
616
|
|
|
617 Compare these example with the examples of @code{apply}.
|
|
|
618 @end defun
|
|
|
619
|
|
|
620 @defun apply function &rest arguments
|
|
|
621 @code{apply} calls @var{function} with @var{arguments}, just like
|
|
|
622 @code{funcall} but with one difference: the last of @var{arguments} is a
|
|
|
623 list of arguments to give to @var{function}, rather than a single
|
|
|
624 argument. We also say that @code{apply} @dfn{spreads} this list so that
|
|
|
625 each individual element becomes an argument.
|
|
|
626
|
|
|
627 @code{apply} returns the result of calling @var{function}. As with
|
|
|
628 @code{funcall}, @var{function} must either be a Lisp function or a
|
|
|
629 primitive function; special forms and macros do not make sense in
|
|
|
630 @code{apply}.
|
|
|
631
|
|
|
632 @example
|
|
|
633 @group
|
|
|
634 (setq f 'list)
|
|
|
635 @result{} list
|
|
|
636 @end group
|
|
|
637 @group
|
|
|
638 (apply f 'x 'y 'z)
|
|
|
639 @error{} Wrong type argument: listp, z
|
|
|
640 @end group
|
|
|
641 @group
|
|
|
642 (apply '+ 1 2 '(3 4))
|
|
|
643 @result{} 10
|
|
|
644 @end group
|
|
|
645 @group
|
|
|
646 (apply '+ '(1 2 3 4))
|
|
|
647 @result{} 10
|
|
|
648 @end group
|
|
|
649
|
|
|
650 @group
|
|
|
651 (apply 'append '((a b c) nil (x y z) nil))
|
|
|
652 @result{} (a b c x y z)
|
|
|
653 @end group
|
|
|
654 @end example
|
|
|
655
|
|
|
656 For an interesting example of using @code{apply}, see the description of
|
|
|
657 @code{mapcar}, in @ref{Mapping Functions}.
|
|
|
658 @end defun
|
|
|
659
|
|
|
660 @cindex functionals
|
|
|
661 It is common for Lisp functions to accept functions as arguments or
|
|
|
662 find them in data structures (especially in hook variables and property
|
|
|
663 lists) and call them using @code{funcall} or @code{apply}. Functions
|
|
|
664 that accept function arguments are often called @dfn{functionals}.
|
|
|
665
|
|
|
666 Sometimes, when you call a functional, it is useful to supply a no-op
|
|
|
667 function as the argument. Here are two different kinds of no-op
|
|
|
668 function:
|
|
|
669
|
|
|
670 @defun identity arg
|
|
|
671 This function returns @var{arg} and has no side effects.
|
|
|
672 @end defun
|
|
|
673
|
|
|
674 @defun ignore &rest args
|
|
|
675 This function ignores any arguments and returns @code{nil}.
|
|
|
676 @end defun
|
|
|
677
|
|
|
678 @node Mapping Functions
|
|
|
679 @section Mapping Functions
|
|
|
680 @cindex mapping functions
|
|
|
681
|
|
|
682 A @dfn{mapping function} applies a given function to each element of a
|
|
398
|
683 list or other collection. XEmacs Lisp has several such functions;
|
|
0
|
684 @code{mapcar} and @code{mapconcat}, which scan a list, are described
|
|
398
|
685 here. @xref{Creating Symbols}, for the function @code{mapatoms} which
|
|
|
686 maps over the symbols in an obarray.
|
|
|
687
|
|
|
688 Mapping functions should never modify the sequence being mapped over.
|
|
|
689 The results are unpredictable.
|
|
0
|
690
|
|
|
691 @defun mapcar function sequence
|
|
|
692 @code{mapcar} applies @var{function} to each element of @var{sequence}
|
|
|
693 in turn, and returns a list of the results.
|
|
|
694
|
|
398
|
695 The argument @var{sequence} can be any kind of sequence; that is, a
|
|
|
696 list, a vector, a bit vector, or a string. The result is always a list.
|
|
|
697 The length of the result is the same as the length of @var{sequence}.
|
|
0
|
698
|
|
|
699 @smallexample
|
|
|
700 @group
|
|
|
701 @exdent @r{For example:}
|
|
|
702
|
|
|
703 (mapcar 'car '((a b) (c d) (e f)))
|
|
|
704 @result{} (a c e)
|
|
|
705 (mapcar '1+ [1 2 3])
|
|
|
706 @result{} (2 3 4)
|
|
|
707 (mapcar 'char-to-string "abc")
|
|
|
708 @result{} ("a" "b" "c")
|
|
|
709 @end group
|
|
|
710
|
|
|
711 @group
|
|
|
712 ;; @r{Call each function in @code{my-hooks}.}
|
|
|
713 (mapcar 'funcall my-hooks)
|
|
|
714 @end group
|
|
|
715
|
|
|
716 @group
|
|
|
717 (defun mapcar* (f &rest args)
|
|
|
718 "Apply FUNCTION to successive cars of all ARGS.
|
|
|
719 Return the list of results."
|
|
|
720 ;; @r{If no list is exhausted,}
|
|
|
721 (if (not (memq 'nil args))
|
|
398
|
722 ;; @r{apply function to @sc{car}s.}
|
|
0
|
723 (cons (apply f (mapcar 'car args))
|
|
|
724 (apply 'mapcar* f
|
|
|
725 ;; @r{Recurse for rest of elements.}
|
|
|
726 (mapcar 'cdr args)))))
|
|
|
727 @end group
|
|
|
728
|
|
|
729 @group
|
|
|
730 (mapcar* 'cons '(a b c) '(1 2 3 4))
|
|
|
731 @result{} ((a . 1) (b . 2) (c . 3))
|
|
|
732 @end group
|
|
|
733 @end smallexample
|
|
|
734 @end defun
|
|
|
735
|
|
|
736 @defun mapconcat function sequence separator
|
|
|
737 @code{mapconcat} applies @var{function} to each element of
|
|
|
738 @var{sequence}: the results, which must be strings, are concatenated.
|
|
|
739 Between each pair of result strings, @code{mapconcat} inserts the string
|
|
|
740 @var{separator}. Usually @var{separator} contains a space or comma or
|
|
|
741 other suitable punctuation.
|
|
|
742
|
|
|
743 The argument @var{function} must be a function that can take one
|
|
398
|
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.
|
|
0
|
746
|
|
|
747 @smallexample
|
|
|
748 @group
|
|
|
749 (mapconcat 'symbol-name
|
|
|
750 '(The cat in the hat)
|
|
|
751 " ")
|
|
|
752 @result{} "The cat in the hat"
|
|
|
753 @end group
|
|
|
754
|
|
|
755 @group
|
|
|
756 (mapconcat (function (lambda (x) (format "%c" (1+ x))))
|
|
|
757 "HAL-8000"
|
|
|
758 "")
|
|
|
759 @result{} "IBM.9111"
|
|
|
760 @end group
|
|
|
761 @end smallexample
|
|
|
762 @end defun
|
|
|
763
|
|
|
764 @node Anonymous Functions
|
|
|
765 @section Anonymous Functions
|
|
|
766 @cindex anonymous function
|
|
|
767
|
|
|
768 In Lisp, a function is a list that starts with @code{lambda}, a
|
|
|
769 byte-code function compiled from such a list, or alternatively a
|
|
|
770 primitive subr-object; names are ``extra''. Although usually functions
|
|
|
771 are defined with @code{defun} and given names at the same time, it is
|
|
|
772 occasionally more concise to use an explicit lambda expression---an
|
|
|
773 anonymous function. Such a list is valid wherever a function name is.
|
|
|
774
|
|
|
775 Any method of creating such a list makes a valid function. Even this:
|
|
|
776
|
|
|
777 @smallexample
|
|
|
778 @group
|
|
|
779 (setq silly (append '(lambda (x)) (list (list '+ (* 3 4) 'x))))
|
|
|
780 @result{} (lambda (x) (+ 12 x))
|
|
|
781 @end group
|
|
|
782 @end smallexample
|
|
|
783
|
|
|
784 @noindent
|
|
|
785 This computes a list that looks like @code{(lambda (x) (+ 12 x))} and
|
|
|
786 makes it the value (@emph{not} the function definition!) of
|
|
|
787 @code{silly}.
|
|
|
788
|
|
|
789 Here is how we might call this function:
|
|
|
790
|
|
|
791 @example
|
|
|
792 @group
|
|
|
793 (funcall silly 1)
|
|
|
794 @result{} 13
|
|
|
795 @end group
|
|
|
796 @end example
|
|
|
797
|
|
|
798 @noindent
|
|
|
799 (It does @emph{not} work to write @code{(silly 1)}, because this function
|
|
|
800 is not the @emph{function definition} of @code{silly}. We have not given
|
|
|
801 @code{silly} any function definition, just a value as a variable.)
|
|
|
802
|
|
|
803 Most of the time, anonymous functions are constants that appear in
|
|
|
804 your program. For example, you might want to pass one as an argument
|
|
|
805 to the function @code{mapcar}, which applies any given function to each
|
|
|
806 element of a list. Here we pass an anonymous function that multiplies
|
|
|
807 a number by two:
|
|
|
808
|
|
|
809 @example
|
|
|
810 @group
|
|
|
811 (defun double-each (list)
|
|
|
812 (mapcar '(lambda (x) (* 2 x)) list))
|
|
|
813 @result{} double-each
|
|
|
814 @end group
|
|
|
815 @group
|
|
|
816 (double-each '(2 11))
|
|
|
817 @result{} (4 22)
|
|
|
818 @end group
|
|
|
819 @end example
|
|
|
820
|
|
|
821 @noindent
|
|
|
822 In such cases, we usually use the special form @code{function} instead
|
|
|
823 of simple quotation to quote the anonymous function.
|
|
|
824
|
|
|
825 @defspec function function-object
|
|
|
826 @cindex function quoting
|
|
|
827 This special form returns @var{function-object} without evaluating it.
|
|
|
828 In this, it is equivalent to @code{quote}. However, it serves as a
|
|
|
829 note to the XEmacs Lisp compiler that @var{function-object} is intended
|
|
|
830 to be used only as a function, and therefore can safely be compiled.
|
|
|
831 Contrast this with @code{quote}, in @ref{Quoting}.
|
|
|
832 @end defspec
|
|
|
833
|
|
|
834 Using @code{function} instead of @code{quote} makes a difference
|
|
|
835 inside a function or macro that you are going to compile. For example:
|
|
|
836
|
|
|
837 @example
|
|
|
838 @group
|
|
|
839 (defun double-each (list)
|
|
|
840 (mapcar (function (lambda (x) (* 2 x))) list))
|
|
|
841 @result{} double-each
|
|
|
842 @end group
|
|
|
843 @group
|
|
|
844 (double-each '(2 11))
|
|
|
845 @result{} (4 22)
|
|
|
846 @end group
|
|
|
847 @end example
|
|
|
848
|
|
|
849 @noindent
|
|
|
850 If this definition of @code{double-each} is compiled, the anonymous
|
|
|
851 function is compiled as well. By contrast, in the previous definition
|
|
|
852 where ordinary @code{quote} is used, the argument passed to
|
|
|
853 @code{mapcar} is the precise list shown:
|
|
|
854
|
|
|
855 @example
|
|
|
856 (lambda (x) (* x 2))
|
|
|
857 @end example
|
|
|
858
|
|
|
859 @noindent
|
|
|
860 The Lisp compiler cannot assume this list is a function, even though it
|
|
|
861 looks like one, since it does not know what @code{mapcar} does with the
|
|
|
862 list. Perhaps @code{mapcar} will check that the @sc{car} of the third
|
|
|
863 element is the symbol @code{*}! The advantage of @code{function} is
|
|
|
864 that it tells the compiler to go ahead and compile the constant
|
|
|
865 function.
|
|
|
866
|
|
|
867 We sometimes write @code{function} instead of @code{quote} when
|
|
|
868 quoting the name of a function, but this usage is just a sort of
|
|
|
869 comment.
|
|
|
870
|
|
|
871 @example
|
|
|
872 (function @var{symbol}) @equiv{} (quote @var{symbol}) @equiv{} '@var{symbol}
|
|
|
873 @end example
|
|
|
874
|
|
|
875 See @code{documentation} in @ref{Accessing Documentation}, for a
|
|
|
876 realistic example using @code{function} and an anonymous function.
|
|
|
877
|
|
|
878 @node Function Cells
|
|
|
879 @section Accessing Function Cell Contents
|
|
|
880
|
|
|
881 The @dfn{function definition} of a symbol is the object stored in the
|
|
|
882 function cell of the symbol. The functions described here access, test,
|
|
|
883 and set the function cell of symbols.
|
|
|
884
|
|
|
885 See also the function @code{indirect-function} in @ref{Function
|
|
|
886 Indirection}.
|
|
|
887
|
|
|
888 @defun symbol-function symbol
|
|
|
889 @kindex void-function
|
|
|
890 This returns the object in the function cell of @var{symbol}. If the
|
|
|
891 symbol's function cell is void, a @code{void-function} error is
|
|
|
892 signaled.
|
|
|
893
|
|
|
894 This function does not check that the returned object is a legitimate
|
|
|
895 function.
|
|
|
896
|
|
|
897 @example
|
|
|
898 @group
|
|
|
899 (defun bar (n) (+ n 2))
|
|
|
900 @result{} bar
|
|
|
901 @end group
|
|
|
902 @group
|
|
|
903 (symbol-function 'bar)
|
|
|
904 @result{} (lambda (n) (+ n 2))
|
|
|
905 @end group
|
|
|
906 @group
|
|
|
907 (fset 'baz 'bar)
|
|
|
908 @result{} bar
|
|
|
909 @end group
|
|
|
910 @group
|
|
|
911 (symbol-function 'baz)
|
|
|
912 @result{} bar
|
|
|
913 @end group
|
|
|
914 @end example
|
|
|
915 @end defun
|
|
|
916
|
|
|
917 @cindex void function cell
|
|
|
918 If you have never given a symbol any function definition, we say that
|
|
|
919 that symbol's function cell is @dfn{void}. In other words, the function
|
|
|
920 cell does not have any Lisp object in it. If you try to call such a symbol
|
|
|
921 as a function, it signals a @code{void-function} error.
|
|
|
922
|
|
|
923 Note that void is not the same as @code{nil} or the symbol
|
|
|
924 @code{void}. The symbols @code{nil} and @code{void} are Lisp objects,
|
|
|
925 and can be stored into a function cell just as any other object can be
|
|
|
926 (and they can be valid functions if you define them in turn with
|
|
|
927 @code{defun}). A void function cell contains no object whatsoever.
|
|
|
928
|
|
|
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
|
|
|
931 can make it void once more using @code{fmakunbound}.
|
|
|
932
|
|
|
933 @defun fboundp symbol
|
|
|
934 This function returns @code{t} if the symbol has an object in its
|
|
|
935 function cell, @code{nil} otherwise. It does not check that the object
|
|
|
936 is a legitimate function.
|
|
|
937 @end defun
|
|
|
938
|
|
|
939 @defun fmakunbound symbol
|
|
|
940 This function makes @var{symbol}'s function cell void, so that a
|
|
|
941 subsequent attempt to access this cell will cause a @code{void-function}
|
|
|
942 error. (See also @code{makunbound}, in @ref{Local Variables}.)
|
|
|
943
|
|
|
944 @example
|
|
|
945 @group
|
|
|
946 (defun foo (x) x)
|
|
|
947 @result{} x
|
|
|
948 @end group
|
|
|
949 @group
|
|
|
950 (foo 1)
|
|
|
951 @result{}1
|
|
|
952 @end group
|
|
|
953 @group
|
|
|
954 (fmakunbound 'foo)
|
|
|
955 @result{} x
|
|
|
956 @end group
|
|
|
957 @group
|
|
|
958 (foo 1)
|
|
|
959 @error{} Symbol's function definition is void: foo
|
|
|
960 @end group
|
|
|
961 @end example
|
|
|
962 @end defun
|
|
|
963
|
|
|
964 @defun fset symbol object
|
|
|
965 This function stores @var{object} in the function cell of @var{symbol}.
|
|
|
966 The result is @var{object}. Normally @var{object} should be a function
|
|
|
967 or the name of a function, but this is not checked.
|
|
|
968
|
|
|
969 There are three normal uses of this function:
|
|
|
970
|
|
|
971 @itemize @bullet
|
|
|
972 @item
|
|
|
973 Copying one symbol's function definition to another. (In other words,
|
|
|
974 making an alternate name for a function.)
|
|
|
975
|
|
|
976 @item
|
|
|
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}
|
|
|
979 to give a symbol @code{s1} a function definition which is another symbol
|
|
|
980 @code{s2}; then @code{s1} serves as an alias for whatever definition
|
|
|
981 @code{s2} presently has.
|
|
|
982
|
|
|
983 @item
|
|
|
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
|
|
|
986 @code{fset}.
|
|
|
987 @end itemize
|
|
|
988
|
|
|
989 Here are examples of the first two uses:
|
|
|
990
|
|
|
991 @example
|
|
|
992 @group
|
|
|
993 ;; @r{Give @code{first} the same definition @code{car} has.}
|
|
|
994 (fset 'first (symbol-function 'car))
|
|
|
995 @result{} #<subr car>
|
|
|
996 @end group
|
|
|
997 @group
|
|
|
998 (first '(1 2 3))
|
|
|
999 @result{} 1
|
|
|
1000 @end group
|
|
|
1001
|
|
|
1002 @group
|
|
|
1003 ;; @r{Make the symbol @code{car} the function definition of @code{xfirst}.}
|
|
|
1004 (fset 'xfirst 'car)
|
|
|
1005 @result{} car
|
|
|
1006 @end group
|
|
|
1007 @group
|
|
|
1008 (xfirst '(1 2 3))
|
|
|
1009 @result{} 1
|
|
|
1010 @end group
|
|
|
1011 @group
|
|
|
1012 (symbol-function 'xfirst)
|
|
|
1013 @result{} car
|
|
|
1014 @end group
|
|
|
1015 @group
|
|
|
1016 (symbol-function (symbol-function 'xfirst))
|
|
|
1017 @result{} #<subr car>
|
|
|
1018 @end group
|
|
|
1019
|
|
|
1020 @group
|
|
|
1021 ;; @r{Define a named keyboard macro.}
|
|
|
1022 (fset 'kill-two-lines "\^u2\^k")
|
|
|
1023 @result{} "\^u2\^k"
|
|
|
1024 @end group
|
|
|
1025 @end example
|
|
|
1026
|
|
|
1027 See also the related functions @code{define-function} and
|
|
|
1028 @code{defalias}, in @ref{Defining Functions}.
|
|
|
1029 @end defun
|
|
|
1030
|
|
|
1031 When writing a function that extends a previously defined function,
|
|
|
1032 the following idiom is sometimes used:
|
|
|
1033
|
|
|
1034 @example
|
|
|
1035 (fset 'old-foo (symbol-function 'foo))
|
|
|
1036 (defun foo ()
|
|
|
1037 "Just like old-foo, except more so."
|
|
|
1038 @group
|
|
|
1039 (old-foo)
|
|
|
1040 (more-so))
|
|
|
1041 @end group
|
|
|
1042 @end example
|
|
|
1043
|
|
|
1044 @noindent
|
|
|
1045 This does not work properly if @code{foo} has been defined to autoload.
|
|
|
1046 In such a case, when @code{foo} calls @code{old-foo}, Lisp attempts
|
|
|
1047 to define @code{old-foo} by loading a file. Since this presumably
|
|
|
1048 defines @code{foo} rather than @code{old-foo}, it does not produce the
|
|
|
1049 proper results. The only way to avoid this problem is to make sure the
|
|
|
1050 file is loaded before moving aside the old definition of @code{foo}.
|
|
|
1051
|
|
|
1052 But it is unmodular and unclean, in any case, for a Lisp file to
|
|
|
1053 redefine a function defined elsewhere.
|
|
|
1054
|
|
|
1055 @node Inline Functions
|
|
|
1056 @section Inline Functions
|
|
|
1057 @cindex inline functions
|
|
|
1058
|
|
|
1059 @findex defsubst
|
|
|
1060 You can define an @dfn{inline function} by using @code{defsubst} instead
|
|
|
1061 of @code{defun}. An inline function works just like an ordinary
|
|
|
1062 function except for one thing: when you compile a call to the function,
|
|
|
1063 the function's definition is open-coded into the caller.
|
|
|
1064
|
|
|
1065 Making a function inline makes explicit calls run faster. But it also
|
|
|
1066 has disadvantages. For one thing, it reduces flexibility; if you change
|
|
|
1067 the definition of the function, calls already inlined still use the old
|
|
|
1068 definition until you recompile them. Since the flexibility of
|
|
|
1069 redefining functions is an important feature of XEmacs, you should not
|
|
|
1070 make a function inline unless its speed is really crucial.
|
|
|
1071
|
|
|
1072 Another disadvantage is that making a large function inline can increase
|
|
|
1073 the size of compiled code both in files and in memory. Since the speed
|
|
|
1074 advantage of inline functions is greatest for small functions, you
|
|
|
1075 generally should not make large functions inline.
|
|
|
1076
|
|
|
1077 It's possible to define a macro to expand into the same code that an
|
|
|
1078 inline function would execute. But the macro would have a limitation:
|
|
|
1079 you can use it only explicitly---a macro cannot be called with
|
|
|
1080 @code{apply}, @code{mapcar} and so on. Also, it takes some work to
|
|
|
1081 convert an ordinary function into a macro. (@xref{Macros}.) To convert
|
|
|
1082 it into an inline function is very easy; simply replace @code{defun}
|
|
|
1083 with @code{defsubst}. Since each argument of an inline function is
|
|
|
1084 evaluated exactly once, you needn't worry about how many times the
|
|
|
1085 body uses the arguments, as you do for macros. (@xref{Argument
|
|
|
1086 Evaluation}.)
|
|
|
1087
|
|
|
1088 Inline functions can be used and open-coded later on in the same file,
|
|
|
1089 following the definition, just like macros.
|
|
|
1090
|
|
|
1091 @c Emacs versions prior to 19 did not have inline functions.
|
|
|
1092
|
|
|
1093 @node Related Topics
|
|
|
1094 @section Other Topics Related to Functions
|
|
|
1095
|
|
|
1096 Here is a table of several functions that do things related to
|
|
|
1097 function calling and function definitions. They are documented
|
|
|
1098 elsewhere, but we provide cross references here.
|
|
|
1099
|
|
|
1100 @table @code
|
|
|
1101 @item apply
|
|
|
1102 See @ref{Calling Functions}.
|
|
|
1103
|
|
|
1104 @item autoload
|
|
|
1105 See @ref{Autoload}.
|
|
|
1106
|
|
|
1107 @item call-interactively
|
|
|
1108 See @ref{Interactive Call}.
|
|
|
1109
|
|
|
1110 @item commandp
|
|
|
1111 See @ref{Interactive Call}.
|
|
|
1112
|
|
|
1113 @item documentation
|
|
|
1114 See @ref{Accessing Documentation}.
|
|
|
1115
|
|
|
1116 @item eval
|
|
|
1117 See @ref{Eval}.
|
|
|
1118
|
|
|
1119 @item funcall
|
|
|
1120 See @ref{Calling Functions}.
|
|
|
1121
|
|
|
1122 @item ignore
|
|
|
1123 See @ref{Calling Functions}.
|
|
|
1124
|
|
|
1125 @item indirect-function
|
|
|
1126 See @ref{Function Indirection}.
|
|
|
1127
|
|
|
1128 @item interactive
|
|
|
1129 See @ref{Using Interactive}.
|
|
|
1130
|
|
|
1131 @item interactive-p
|
|
|
1132 See @ref{Interactive Call}.
|
|
|
1133
|
|
|
1134 @item mapatoms
|
|
|
1135 See @ref{Creating Symbols}.
|
|
|
1136
|
|
|
1137 @item mapcar
|
|
|
1138 See @ref{Mapping Functions}.
|
|
|
1139
|
|
|
1140 @item mapconcat
|
|
|
1141 See @ref{Mapping Functions}.
|
|
|
1142
|
|
|
1143 @item undefined
|
|
|
1144 See @ref{Key Lookup}.
|
|
|
1145 @end table
|
|
|
1146
|
