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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/positions.info
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6 @node Positions, Markers, Consoles and Devices, Top
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7 @chapter Positions
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8 @cindex position (in buffer)
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9
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10 A @dfn{position} is the index of a character in the text of a buffer.
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11 More precisely, a position identifies the place between two characters
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12 (or before the first character, or after the last character), so we can
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13 speak of the character before or after a given position. However, we
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14 often speak of the character ``at'' a position, meaning the character
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15 after that position.
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16
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17 Positions are usually represented as integers starting from 1, but can
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18 also be represented as @dfn{markers}---special objects that relocate
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19 automatically when text is inserted or deleted so they stay with the
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20 surrounding characters. @xref{Markers}.
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21
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22 @menu
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23 * Point:: The special position where editing takes place.
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24 * Motion:: Changing point.
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25 * Excursions:: Temporary motion and buffer changes.
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26 * Narrowing:: Restricting editing to a portion of the buffer.
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27 @end menu
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28
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29 @node Point
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30 @section Point
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31 @cindex point
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32
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33 @dfn{Point} is a special buffer position used by many editing
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34 commands, including the self-inserting typed characters and text
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35 insertion functions. Other commands move point through the text
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36 to allow editing and insertion at different places.
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37
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38 Like other positions, point designates a place between two characters
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39 (or before the first character, or after the last character), rather
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40 than a particular character. Usually terminals display the cursor over
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41 the character that immediately follows point; point is actually before
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42 the character on which the cursor sits.
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43
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44 @cindex point with narrowing
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45 The value of point is a number between 1 and the buffer size plus 1.
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46 If narrowing is in effect (@pxref{Narrowing}), then point is constrained
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47 to fall within the accessible portion of the buffer (possibly at one end
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48 of it).
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49
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50 Each buffer has its own value of point, which is independent of the
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51 value of point in other buffers. Each window also has a value of point,
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52 which is independent of the value of point in other windows on the same
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53 buffer. This is why point can have different values in various windows
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54 that display the same buffer. When a buffer appears in only one window,
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55 the buffer's point and the window's point normally have the same value,
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56 so the distinction is rarely important. @xref{Window Point}, for more
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57 details.
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58
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59 @defun point &optional buffer
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60 @cindex current buffer position
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61 This function returns the value of point in @var{buffer}, as an integer.
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62 @var{buffer} defaults to the current buffer if omitted.
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63
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64 @need 700
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65 @example
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66 @group
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67 (point)
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68 @result{} 175
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69 @end group
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70 @end example
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71 @end defun
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72
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73 @defun point-min &optional buffer
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74 This function returns the minimum accessible value of point in
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75 @var{buffer}. This is normally 1, but if narrowing is in effect, it is
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76 the position of the start of the region that you narrowed to.
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77 (@xref{Narrowing}.) @var{buffer} defaults to the current buffer if
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78 omitted.
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79 @end defun
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80
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81 @defun point-max &optional buffer
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82 This function returns the maximum accessible value of point in
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83 @var{buffer}. This is @code{(1+ (buffer-size buffer))}, unless
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84 narrowing is in effect, in which case it is the position of the end of
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85 the region that you narrowed to. (@xref{Narrowing}). @var{buffer}
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86 defaults to the current buffer if omitted.
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87 @end defun
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88
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89 @defun buffer-end flag &optional buffer
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90 This function returns @code{(point-min buffer)} if @var{flag} is less
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91 than 1, @code{(point-max buffer)} otherwise. The argument @var{flag}
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92 must be a number. @var{buffer} defaults to the current buffer if
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93 omitted.
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94 @end defun
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95
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96 @defun buffer-size &optional buffer
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97 This function returns the total number of characters in @var{buffer}.
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98 In the absence of any narrowing (@pxref{Narrowing}), @code{point-max}
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99 returns a value one larger than this. @var{buffer} defaults to the
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100 current buffer if omitted.
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101
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102 @example
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103 @group
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104 (buffer-size)
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105 @result{} 35
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106 @end group
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107 @group
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108 (point-max)
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109 @result{} 36
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110 @end group
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111 @end example
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112 @end defun
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113
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114 @defvar buffer-saved-size
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115 The value of this buffer-local variable is the former length of the
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116 current buffer, as of the last time it was read in, saved or auto-saved.
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117 @end defvar
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118
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119 @node Motion
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120 @section Motion
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121
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122 Motion functions change the value of point, either relative to the
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123 current value of point, relative to the beginning or end of the buffer,
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124 or relative to the edges of the selected window. @xref{Point}.
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125
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126 @menu
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127 * Character Motion:: Moving in terms of characters.
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128 * Word Motion:: Moving in terms of words.
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129 * Buffer End Motion:: Moving to the beginning or end of the buffer.
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130 * Text Lines:: Moving in terms of lines of text.
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131 * Screen Lines:: Moving in terms of lines as displayed.
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132 * List Motion:: Moving by parsing lists and sexps.
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133 * Skipping Characters:: Skipping characters belonging to a certain set.
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134 @end menu
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135
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136 @node Character Motion
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137 @subsection Motion by Characters
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138
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139 These functions move point based on a count of characters.
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140 @code{goto-char} is the fundamental primitive; the other functions use
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141 that.
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142
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143 @deffn Command goto-char position &optional buffer
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144 This function sets point in @code{buffer} to the value @var{position}.
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145 If @var{position} is less than 1, it moves point to the beginning of the
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146 buffer. If @var{position} is greater than the length of the buffer, it
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147 moves point to the end. @var{buffer} defaults to the current buffer if
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148 omitted.
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149
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150 If narrowing is in effect, @var{position} still counts from the
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151 beginning of the buffer, but point cannot go outside the accessible
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152 portion. If @var{position} is out of range, @code{goto-char} moves
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153 point to the beginning or the end of the accessible portion.
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154
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155 When this function is called interactively, @var{position} is the
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156 numeric prefix argument, if provided; otherwise it is read from the
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157 minibuffer.
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158
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159 @code{goto-char} returns @var{position}.
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160 @end deffn
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161
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162 @deffn Command forward-char &optional count buffer
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163 @c @kindex beginning-of-buffer
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164 @c @kindex end-of-buffer
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165 This function moves point @var{count} characters forward, towards the
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166 end of the buffer (or backward, towards the beginning of the buffer, if
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167 @var{count} is negative). If the function attempts to move point past
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168 the beginning or end of the buffer (or the limits of the accessible
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169 portion, when narrowing is in effect), an error is signaled with error
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170 code @code{beginning-of-buffer} or @code{end-of-buffer}. @var{buffer}
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171 defaults to the current buffer if omitted.
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172
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173
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174 In an interactive call, @var{count} is the numeric prefix argument.
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175 @end deffn
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176
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177 @deffn Command backward-char &optional count buffer
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178 This function moves point @var{count} characters backward, towards the
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179 beginning of the buffer (or forward, towards the end of the buffer, if
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180 @var{count} is negative). If the function attempts to move point past
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181 the beginning or end of the buffer (or the limits of the accessible
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182 portion, when narrowing is in effect), an error is signaled with error
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183 code @code{beginning-of-buffer} or @code{end-of-buffer}. @var{buffer}
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184 defaults to the current buffer if omitted.
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185
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186
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187 In an interactive call, @var{count} is the numeric prefix argument.
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188 @end deffn
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189
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190 @node Word Motion
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191 @subsection Motion by Words
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192
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193 These functions for parsing words use the syntax table to decide
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194 whether a given character is part of a word. @xref{Syntax Tables}.
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195
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196 @deffn Command forward-word count &optional buffer
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197 This function moves point forward @var{count} words (or backward if
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198 @var{count} is negative). Normally it returns @code{t}. If this motion
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199 encounters the beginning or end of the buffer, or the limits of the
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200 accessible portion when narrowing is in effect, point stops there and
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201 the value is @code{nil}. @var{buffer} defaults to the current buffer if
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202 omitted.
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203
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204 In an interactive call, @var{count} is set to the numeric prefix
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205 argument.
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206 @end deffn
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207
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208 @deffn Command backward-word count &optional buffer
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209 This function is just like @code{forward-word}, except that it moves
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210 backward until encountering the front of a word, rather than forward.
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211 @var{buffer} defaults to the current buffer if omitted.
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212
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213 In an interactive call, @var{count} is set to the numeric prefix
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214 argument.
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215
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216 This function is rarely used in programs, as it is more efficient to
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217 call @code{forward-word} with a negative argument.
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218 @end deffn
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219
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220 @defvar words-include-escapes
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221 @c Emacs 19 feature
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222 This variable affects the behavior of @code{forward-word} and everything
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223 that uses it. If it is non-@code{nil}, then characters in the
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224 ``escape'' and ``character quote'' syntax classes count as part of
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225 words. Otherwise, they do not.
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226 @end defvar
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227
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228 @node Buffer End Motion
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229 @subsection Motion to an End of the Buffer
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230
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231 To move point to the beginning of the buffer, write:
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232
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233 @example
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234 @group
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235 (goto-char (point-min))
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236 @end group
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237 @end example
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238
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239 @noindent
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240 Likewise, to move to the end of the buffer, use:
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241
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242 @example
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243 @group
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244 (goto-char (point-max))
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245 @end group
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246 @end example
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247
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248 Here are two commands that users use to do these things. They are
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249 documented here to warn you not to use them in Lisp programs, because
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250 they set the mark and display messages in the echo area.
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251
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252 @deffn Command beginning-of-buffer &optional n
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253 This function moves point to the beginning of the buffer (or the limits
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254 of the accessible portion, when narrowing is in effect), setting the
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255 mark at the previous position. If @var{n} is non-@code{nil}, then it
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256 puts point @var{n} tenths of the way from the beginning of the buffer.
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257
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258 In an interactive call, @var{n} is the numeric prefix argument,
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259 if provided; otherwise @var{n} defaults to @code{nil}.
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260
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261 Don't use this function in Lisp programs!
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262 @end deffn
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263
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264 @deffn Command end-of-buffer &optional n
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265 This function moves point to the end of the buffer (or the limits of
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266 the accessible portion, when narrowing is in effect), setting the mark
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267 at the previous position. If @var{n} is non-@code{nil}, then it puts
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268 point @var{n} tenths of the way from the end of the buffer.
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269
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270 In an interactive call, @var{n} is the numeric prefix argument,
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271 if provided; otherwise @var{n} defaults to @code{nil}.
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272
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273 Don't use this function in Lisp programs!
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274 @end deffn
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275
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276 @node Text Lines
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277 @subsection Motion by Text Lines
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278 @cindex lines
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279
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280 Text lines are portions of the buffer delimited by newline characters,
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281 which are regarded as part of the previous line. The first text line
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282 begins at the beginning of the buffer, and the last text line ends at
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283 the end of the buffer whether or not the last character is a newline.
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284 The division of the buffer into text lines is not affected by the width
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285 of the window, by line continuation in display, or by how tabs and
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286 control characters are displayed.
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287
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288 @deffn Command goto-line line
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289 This function moves point to the front of the @var{line}th line,
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290 counting from line 1 at beginning of the buffer. If @var{line} is less
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291 than 1, it moves point to the beginning of the buffer. If @var{line} is
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292 greater than the number of lines in the buffer, it moves point to the
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293 end of the buffer---that is, the @emph{end of the last line} of the
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294 buffer. This is the only case in which @code{goto-line} does not
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295 necessarily move to the beginning of a line.
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296
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297 If narrowing is in effect, then @var{line} still counts from the
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298 beginning of the buffer, but point cannot go outside the accessible
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299 portion. So @code{goto-line} moves point to the beginning or end of the
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300 accessible portion, if the line number specifies an inaccessible
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301 position.
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302
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303 The return value of @code{goto-line} is the difference between
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304 @var{line} and the line number of the line to which point actually was
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305 able to move (in the full buffer, before taking account of narrowing).
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306 Thus, the value is positive if the scan encounters the real end of the
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307 buffer. The value is zero if scan encounters the end of the accessible
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308 portion but not the real end of the buffer.
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309
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310 In an interactive call, @var{line} is the numeric prefix argument if
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311 one has been provided. Otherwise @var{line} is read in the minibuffer.
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312 @end deffn
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313
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314 @deffn Command beginning-of-line &optional count buffer
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315 This function moves point to the beginning of the current line. With an
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316 argument @var{count} not @code{nil} or 1, it moves forward
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317 @var{count}@minus{}1 lines and then to the beginning of the line.
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318 @var{buffer} defaults to the current buffer if omitted.
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319
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320 If this function reaches the end of the buffer (or of the accessible
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321 portion, if narrowing is in effect), it positions point there. No error
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322 is signaled.
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323 @end deffn
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324
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325 @deffn Command end-of-line &optional count buffer
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326 This function moves point to the end of the current line. With an
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327 argument @var{count} not @code{nil} or 1, it moves forward
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328 @var{count}@minus{}1 lines and then to the end of the line.
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329 @var{buffer} defaults to the current buffer if omitted.
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330
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331 If this function reaches the end of the buffer (or of the accessible
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332 portion, if narrowing is in effect), it positions point there. No error
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333 is signaled.
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334 @end deffn
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335
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336 @deffn Command forward-line &optional count buffer
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337 @cindex beginning of line
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338 This function moves point forward @var{count} lines, to the beginning of
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339 the line. If @var{count} is negative, it moves point
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340 @minus{}@var{count} lines backward, to the beginning of a line. If
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341 @var{count} is zero, it moves point to the beginning of the current
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342 line. @var{buffer} defaults to the current buffer if omitted.
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343
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344 If @code{forward-line} encounters the beginning or end of the buffer (or
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345 of the accessible portion) before finding that many lines, it sets point
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346 there. No error is signaled.
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347
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348 @code{forward-line} returns the difference between @var{count} and the
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349 number of lines actually moved. If you attempt to move down five lines
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350 from the beginning of a buffer that has only three lines, point stops at
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351 the end of the last line, and the value will be 2.
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352
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353 In an interactive call, @var{count} is the numeric prefix argument.
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354 @end deffn
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355
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356 @defun count-lines start end
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357 @cindex lines in region
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358 This function returns the number of lines between the positions
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359 @var{start} and @var{end} in the current buffer. If @var{start} and
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360 @var{end} are equal, then it returns 0. Otherwise it returns at least
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361 1, even if @var{start} and @var{end} are on the same line. This is
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362 because the text between them, considered in isolation, must contain at
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363 least one line unless it is empty.
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364
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365 Here is an example of using @code{count-lines}:
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366
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367 @example
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368 @group
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369 (defun current-line ()
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370 "Return the vertical position of point@dots{}"
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371 (+ (count-lines (window-start) (point))
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372 (if (= (current-column) 0) 1 0)
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373 -1))
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374 @end group
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375 @end example
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376 @end defun
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377
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378 @ignore
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379 @c ================
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380 The @code{previous-line} and @code{next-line} commands are functions
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381 that should not be used in programs. They are for users and are
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382 mentioned here only for completeness.
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383
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384 @deffn Command previous-line count
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385 @cindex goal column
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386 This function moves point up @var{count} lines (down if @var{count}
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387 is negative). In moving, it attempts to keep point in the ``goal column''
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388 (normally the same column that it was at the beginning of the move).
|
|
|
389
|
|
|
390 If there is no character in the target line exactly under the current
|
|
|
391 column, point is positioned after the character in that line which
|
|
|
392 spans this column, or at the end of the line if it is not long enough.
|
|
|
393
|
|
|
394 If it attempts to move beyond the top or bottom of the buffer (or clipped
|
|
|
395 region), then point is positioned in the goal column in the top or
|
|
|
396 bottom line. No error is signaled.
|
|
|
397
|
|
|
398 In an interactive call, @var{count} will be the numeric
|
|
|
399 prefix argument.
|
|
|
400
|
|
|
401 The command @code{set-goal-column} can be used to create a semipermanent
|
|
|
402 goal column to which this command always moves. Then it does not try to
|
|
|
403 move vertically.
|
|
|
404
|
|
|
405 If you are thinking of using this in a Lisp program, consider using
|
|
|
406 @code{forward-line} with a negative argument instead. It is usually easier
|
|
|
407 to use and more reliable (no dependence on goal column, etc.).
|
|
|
408 @end deffn
|
|
|
409
|
|
|
410 @deffn Command next-line count
|
|
|
411 This function moves point down @var{count} lines (up if @var{count}
|
|
|
412 is negative). In moving, it attempts to keep point in the ``goal column''
|
|
|
413 (normally the same column that it was at the beginning of the move).
|
|
|
414
|
|
|
415 If there is no character in the target line exactly under the current
|
|
|
416 column, point is positioned after the character in that line which
|
|
|
417 spans this column, or at the end of the line if it is not long enough.
|
|
|
418
|
|
|
419 If it attempts to move beyond the top or bottom of the buffer (or clipped
|
|
|
420 region), then point is positioned in the goal column in the top or
|
|
|
421 bottom line. No error is signaled.
|
|
|
422
|
|
|
423 In the case where the @var{count} is 1, and point is on the last
|
|
|
424 line of the buffer (or clipped region), a new empty line is inserted at the
|
|
|
425 end of the buffer (or clipped region) and point moved there.
|
|
|
426
|
|
|
427 In an interactive call, @var{count} will be the numeric
|
|
|
428 prefix argument.
|
|
|
429
|
|
|
430 The command @code{set-goal-column} can be used to create a semipermanent
|
|
|
431 goal column to which this command always moves. Then it does not try to
|
|
|
432 move vertically.
|
|
|
433
|
|
|
434 If you are thinking of using this in a Lisp program, consider using
|
|
|
435 @code{forward-line} instead. It is usually easier
|
|
|
436 to use and more reliable (no dependence on goal column, etc.).
|
|
|
437 @end deffn
|
|
|
438
|
|
|
439 @c ================
|
|
|
440 @end ignore
|
|
|
441
|
|
|
442 Also see the functions @code{bolp} and @code{eolp} in @ref{Near Point}.
|
|
|
443 These functions do not move point, but test whether it is already at the
|
|
|
444 beginning or end of a line.
|
|
|
445
|
|
|
446 @node Screen Lines
|
|
|
447 @subsection Motion by Screen Lines
|
|
|
448
|
|
|
449 The line functions in the previous section count text lines, delimited
|
|
|
450 only by newline characters. By contrast, these functions count screen
|
|
|
451 lines, which are defined by the way the text appears on the screen. A
|
|
|
452 text line is a single screen line if it is short enough to fit the width
|
|
|
453 of the selected window, but otherwise it may occupy several screen
|
|
|
454 lines.
|
|
|
455
|
|
|
456 In some cases, text lines are truncated on the screen rather than
|
|
|
457 continued onto additional screen lines. In these cases,
|
|
|
458 @code{vertical-motion} moves point much like @code{forward-line}.
|
|
|
459 @xref{Truncation}.
|
|
|
460
|
|
|
461 Because the width of a given string depends on the flags that control
|
|
|
462 the appearance of certain characters, @code{vertical-motion} behaves
|
|
|
463 differently, for a given piece of text, depending on the buffer it is
|
|
|
464 in, and even on the selected window (because the width, the truncation
|
|
|
465 flag, and display table may vary between windows). @xref{Usual
|
|
|
466 Display}.
|
|
|
467
|
|
|
468 These functions scan text to determine where screen lines break, and
|
|
|
469 thus take time proportional to the distance scanned. If you intend to
|
|
|
470 use them heavily, Emacs provides caches which may improve the
|
|
|
471 performance of your code. @xref{Text Lines, cache-long-line-scans}.
|
|
|
472
|
|
|
473
|
|
|
474 @defun vertical-motion count &optional window
|
|
|
475 This function moves point to the start of the screen line @var{count}
|
|
|
476 screen lines down from the screen line containing point. If @var{count}
|
|
|
477 is negative, it moves up instead.
|
|
|
478
|
|
|
479 @code{vertical-motion} returns the number of lines moved. The value may
|
|
|
480 be less in absolute value than @var{count} if the beginning or end of
|
|
|
481 the buffer was reached.
|
|
|
482
|
|
|
483 The window @var{window} is used for obtaining parameters such as the
|
|
|
484 width, the horizontal scrolling, and the display table. But
|
|
|
485 @code{vertical-motion} always operates on the current buffer, even if
|
|
|
486 @var{window} currently displays some other buffer.
|
|
|
487 @end defun
|
|
|
488
|
|
|
489 @deffn Command move-to-window-line count &optional window
|
|
|
490 This function moves point with respect to the text currently displayed
|
|
|
491 in @var{window}, which defaults to the selected window. It moves point
|
|
|
492 to the beginning of the screen line @var{count} screen lines from the
|
|
|
493 top of the window. If @var{count} is negative, that specifies a
|
|
|
494 position @w{@minus{}@var{count}} lines from the bottom (or the last line
|
|
|
495 of the buffer, if the buffer ends above the specified screen position).
|
|
|
496
|
|
|
497 If @var{count} is @code{nil}, then point moves to the beginning of the
|
|
|
498 line in the middle of the window. If the absolute value of @var{count}
|
|
|
499 is greater than the size of the window, then point moves to the place
|
|
|
500 that would appear on that screen line if the window were tall enough.
|
|
|
501 This will probably cause the next redisplay to scroll to bring that
|
|
|
502 location onto the screen.
|
|
|
503
|
|
|
504 In an interactive call, @var{count} is the numeric prefix argument.
|
|
|
505
|
|
|
506 The value returned is the window line number point has moved to, with
|
|
|
507 the top line in the window numbered 0.
|
|
|
508 @end deffn
|
|
|
509
|
|
|
510 @ignore Not in XEmacs
|
|
|
511 @defun compute-motion from frompos to topos width offsets window
|
|
|
512 This function scans the current buffer, calculating screen positions.
|
|
|
513 It scans the buffer forward from position @var{from}, assuming that is
|
|
|
514 at screen coordinates @var{frompos}, to position @var{to} or coordinates
|
|
|
515 @var{topos}, whichever comes first. It returns the ending buffer
|
|
|
516 position and screen coordinates.
|
|
|
517
|
|
|
518 The coordinate arguments @var{frompos} and @var{topos} are cons cells of
|
|
|
519 the form @code{(@var{hpos} . @var{vpos})}.
|
|
|
520
|
|
|
521 The argument @var{width} is the number of columns available to display
|
|
|
522 text; this affects handling of continuation lines. Use the value
|
|
|
523 returned by @code{window-width} for the window of your choice;
|
|
|
524 normally, use @code{(window-width @var{window})}.
|
|
|
525
|
|
|
526 The argument @var{offsets} is either @code{nil} or a cons cell of the
|
|
|
527 form @code{(@var{hscroll} . @var{tab-offset})}. Here @var{hscroll} is
|
|
|
528 the number of columns not being displayed at the left margin; most
|
|
|
529 callers get this from @code{window-hscroll}. Meanwhile,
|
|
|
530 @var{tab-offset} is the offset between column numbers on the screen and
|
|
|
531 column numbers in the buffer. This can be nonzero in a continuation
|
|
|
532 line, when the previous screen lines' widths do not add up to a multiple
|
|
|
533 of @code{tab-width}. It is always zero in a non-continuation line.
|
|
|
534
|
|
|
535 The window @var{window} serves only to specify which display table to
|
|
|
536 use. @code{compute-motion} always operates on the current buffer,
|
|
|
537 regardless of what buffer is displayed in @var{window}.
|
|
|
538
|
|
|
539 The return value is a list of five elements:
|
|
|
540
|
|
|
541 @example
|
|
|
542 (@var{pos} @var{vpos} @var{hpos} @var{prevhpos} @var{contin})
|
|
|
543 @end example
|
|
|
544
|
|
|
545 @noindent
|
|
|
546 Here @var{pos} is the buffer position where the scan stopped, @var{vpos}
|
|
|
547 is the vertical screen position, and @var{hpos} is the horizontal screen
|
|
|
548 position.
|
|
|
549
|
|
|
550 The result @var{prevhpos} is the horizontal position one character back
|
|
|
551 from @var{pos}. The result @var{contin} is @code{t} if the last line
|
|
|
552 was continued after (or within) the previous character.
|
|
|
553
|
|
|
554 For example, to find the buffer position of column @var{col} of line
|
|
|
555 @var{line} of a certain window, pass the window's display start location
|
|
|
556 as @var{from} and the window's upper-left coordinates as @var{frompos}.
|
|
|
557 Pass the buffer's @code{(point-max)} as @var{to}, to limit the scan to
|
|
|
558 the end of the accessible portion of the buffer, and pass @var{line} and
|
|
|
559 @var{col} as @var{topos}. Here's a function that does this:
|
|
|
560
|
|
|
561 @example
|
|
|
562 (defun coordinates-of-position (col line)
|
|
|
563 (car (compute-motion (window-start)
|
|
|
564 '(0 . 0)
|
|
|
565 (point-max)
|
|
|
566 (cons col line)
|
|
|
567 (window-width)
|
|
|
568 (cons (window-hscroll) 0)
|
|
|
569 (selected-window))))
|
|
|
570 @end example
|
|
|
571
|
|
|
572 When you use @code{compute-motion} for the minibuffer, you need to use
|
|
|
573 @code{minibuffer-prompt-width} to get the horizontal position of the
|
|
|
574 beginning of the first screen line. @xref{Minibuffer Misc}.
|
|
|
575 @end defun
|
|
|
576 @end ignore
|
|
|
577
|
|
|
578 @node List Motion
|
|
|
579 @subsection Moving over Balanced Expressions
|
|
|
580 @cindex sexp motion
|
|
|
581 @cindex Lisp expression motion
|
|
|
582 @cindex list motion
|
|
|
583
|
|
|
584 Here are several functions concerned with balanced-parenthesis
|
|
|
585 expressions (also called @dfn{sexps} in connection with moving across
|
|
|
586 them in XEmacs). The syntax table controls how these functions interpret
|
|
|
587 various characters; see @ref{Syntax Tables}. @xref{Parsing
|
|
|
588 Expressions}, for lower-level primitives for scanning sexps or parts of
|
|
|
589 sexps. For user-level commands, see @ref{Lists and Sexps,,, emacs, XEmacs
|
|
|
590 Reference Manual}.
|
|
|
591
|
|
|
592 @deffn Command forward-list &optional arg
|
|
|
593 This function moves forward across @var{arg} balanced groups of
|
|
|
594 parentheses. (Other syntactic entities such as words or paired string
|
|
|
595 quotes are ignored.) @var{arg} defaults to 1 if omitted. If @var{arg}
|
|
|
596 is negative, move backward across that many groups of parentheses.
|
|
|
597 @end deffn
|
|
|
598
|
|
|
599 @deffn Command backward-list &optional arg
|
|
|
600 This function moves backward across @var{arg} balanced groups of
|
|
|
601 parentheses. (Other syntactic entities such as words or paired string
|
|
|
602 quotes are ignored.) @var{arg} defaults to 1 if omitted. If @var{arg}
|
|
|
603 is negative, move forward across that many groups of parentheses.
|
|
|
604 @end deffn
|
|
|
605
|
|
|
606 @deffn Command up-list arg
|
|
|
607 This function moves forward out of @var{arg} levels of parentheses.
|
|
|
608 A negative argument means move backward but still to a less deep spot.
|
|
|
609 @end deffn
|
|
|
610
|
|
|
611 @deffn Command down-list arg
|
|
|
612 This function moves forward into @var{arg} levels of parentheses. A
|
|
|
613 negative argument means move backward but still go
|
|
|
614 deeper in parentheses (@minus{}@var{arg} levels).
|
|
|
615 @end deffn
|
|
|
616
|
|
|
617 @deffn Command forward-sexp &optional arg
|
|
|
618 This function moves forward across @var{arg} balanced expressions.
|
|
|
619 Balanced expressions include both those delimited by parentheses and
|
|
|
620 other kinds, such as words and string constants. @var{arg} defaults to
|
|
|
621 1 if omitted. If @var{arg} is negative, move backward across that many
|
|
|
622 balanced expressions. For example,
|
|
|
623
|
|
|
624 @example
|
|
|
625 @group
|
|
|
626 ---------- Buffer: foo ----------
|
|
|
627 (concat@point{} "foo " (car x) y z)
|
|
|
628 ---------- Buffer: foo ----------
|
|
|
629 @end group
|
|
|
630
|
|
|
631 @group
|
|
|
632 (forward-sexp 3)
|
|
|
633 @result{} nil
|
|
|
634
|
|
|
635 ---------- Buffer: foo ----------
|
|
|
636 (concat "foo " (car x) y@point{} z)
|
|
|
637 ---------- Buffer: foo ----------
|
|
|
638 @end group
|
|
|
639 @end example
|
|
|
640 @end deffn
|
|
|
641
|
|
|
642 @deffn Command backward-sexp &optional arg
|
|
|
643 This function moves backward across @var{arg} balanced expressions.
|
|
|
644 @var{arg} defaults to 1 if omitted. If @var{arg} is negative, move
|
|
|
645 forward across that many balanced expressions.
|
|
|
646 @end deffn
|
|
|
647
|
|
|
648 @deffn Command beginning-of-defun &optional arg
|
|
|
649 This function moves back to the @var{arg}th beginning of a defun. If
|
|
|
650 @var{arg} is negative, this actually moves forward, but it still moves
|
|
|
651 to the beginning of a defun, not to the end of one. @var{arg} defaults
|
|
|
652 to 1 if omitted.
|
|
|
653 @end deffn
|
|
|
654
|
|
|
655 @deffn Command end-of-defun &optional arg
|
|
|
656 This function moves forward to the @var{arg}th end of a defun. If
|
|
|
657 @var{arg} is negative, this actually moves backward, but it still moves
|
|
|
658 to the end of a defun, not to the beginning of one. @var{arg} defaults
|
|
|
659 to 1 if omitted.
|
|
|
660 @end deffn
|
|
|
661
|
|
|
662 @defopt defun-prompt-regexp
|
|
|
663 If non-@code{nil}, this variable holds a regular expression that
|
|
|
664 specifies what text can appear before the open-parenthesis that starts a
|
|
|
665 defun. That is to say, a defun begins on a line that starts with a
|
|
|
666 match for this regular expression, followed by a character with
|
|
|
667 open-parenthesis syntax.
|
|
|
668 @end defopt
|
|
|
669
|
|
|
670 @node Skipping Characters
|
|
|
671 @subsection Skipping Characters
|
|
|
672 @cindex skipping characters
|
|
|
673
|
|
|
674 The following two functions move point over a specified set of
|
|
|
675 characters. For example, they are often used to skip whitespace. For
|
|
|
676 related functions, see @ref{Motion and Syntax}.
|
|
|
677
|
|
|
678 @defun skip-chars-forward character-set &optional limit buffer
|
|
|
679 This function moves point in @var{buffer} forward, skipping over a
|
|
|
680 given set of characters. It examines the character following point,
|
|
|
681 then advances point if the character matches @var{character-set}. This
|
|
|
682 continues until it reaches a character that does not match. The
|
|
|
683 function returns @code{nil}. @var{buffer} defaults to the current
|
|
|
684 buffer if omitted.
|
|
|
685
|
|
|
686 The argument @var{character-set} is like the inside of a
|
|
|
687 @samp{[@dots{}]} in a regular expression except that @samp{]} is never
|
|
|
688 special and @samp{\} quotes @samp{^}, @samp{-} or @samp{\}. Thus,
|
|
|
689 @code{"a-zA-Z"} skips over all letters, stopping before the first
|
|
|
690 nonletter, and @code{"^a-zA-Z}" skips nonletters stopping before the
|
|
|
691 first letter. @xref{Regular Expressions}.
|
|
|
692
|
|
|
693 If @var{limit} is supplied (it must be a number or a marker), it
|
|
|
694 specifies the maximum position in the buffer that point can be skipped
|
|
|
695 to. Point will stop at or before @var{limit}.
|
|
|
696
|
|
|
697 In the following example, point is initially located directly before the
|
|
|
698 @samp{T}. After the form is evaluated, point is located at the end of
|
|
|
699 that line (between the @samp{t} of @samp{hat} and the newline). The
|
|
|
700 function skips all letters and spaces, but not newlines.
|
|
|
701
|
|
|
702 @example
|
|
|
703 @group
|
|
|
704 ---------- Buffer: foo ----------
|
|
|
705 I read "@point{}The cat in the hat
|
|
|
706 comes back" twice.
|
|
|
707 ---------- Buffer: foo ----------
|
|
|
708 @end group
|
|
|
709
|
|
|
710 @group
|
|
|
711 (skip-chars-forward "a-zA-Z ")
|
|
|
712 @result{} nil
|
|
|
713
|
|
|
714 ---------- Buffer: foo ----------
|
|
|
715 I read "The cat in the hat@point{}
|
|
|
716 comes back" twice.
|
|
|
717 ---------- Buffer: foo ----------
|
|
|
718 @end group
|
|
|
719 @end example
|
|
|
720 @end defun
|
|
|
721
|
|
|
722 @defun skip-chars-backward character-set &optional limit buffer
|
|
|
723 This function moves point backward, skipping characters that match
|
|
|
724 @var{character-set}, until @var{limit}. It just like
|
|
|
725 @code{skip-chars-forward} except for the direction of motion.
|
|
|
726 @end defun
|
|
|
727
|
|
|
728 @node Excursions
|
|
|
729 @section Excursions
|
|
|
730 @cindex excursion
|
|
|
731
|
|
|
732 It is often useful to move point ``temporarily'' within a localized
|
|
|
733 portion of the program, or to switch buffers temporarily. This is
|
|
|
734 called an @dfn{excursion}, and it is done with the @code{save-excursion}
|
|
|
735 special form. This construct saves the current buffer and its values of
|
|
|
736 point and the mark so they can be restored after the completion of the
|
|
|
737 excursion.
|
|
|
738
|
|
|
739 The forms for saving and restoring the configuration of windows are
|
|
|
740 described elsewhere (see @ref{Window Configurations} and @pxref{Frame
|
|
|
741 Configurations}).
|
|
|
742
|
|
|
743 @defspec save-excursion forms@dots{}
|
|
|
744 @cindex mark excursion
|
|
|
745 @cindex point excursion
|
|
|
746 @cindex current buffer excursion
|
|
|
747 The @code{save-excursion} special form saves the identity of the current
|
|
|
748 buffer and the values of point and the mark in it, evaluates
|
|
|
749 @var{forms}, and finally restores the buffer and its saved values of
|
|
|
750 point and the mark. All three saved values are restored even in case of
|
|
|
751 an abnormal exit via @code{throw} or error (@pxref{Nonlocal Exits}).
|
|
|
752
|
|
|
753 The @code{save-excursion} special form is the standard way to switch
|
|
|
754 buffers or move point within one part of a program and avoid affecting
|
|
|
755 the rest of the program. It is used more than 500 times in the Lisp
|
|
|
756 sources of XEmacs.
|
|
|
757
|
|
|
758 @code{save-excursion} does not save the values of point and the mark for
|
|
|
759 other buffers, so changes in other buffers remain in effect after
|
|
|
760 @code{save-excursion} exits.
|
|
|
761
|
|
|
762 @cindex window excursions
|
|
|
763 Likewise, @code{save-excursion} does not restore window-buffer
|
|
|
764 correspondences altered by functions such as @code{switch-to-buffer}.
|
|
|
765 One way to restore these correspondences, and the selected window, is to
|
|
|
766 use @code{save-window-excursion} inside @code{save-excursion}
|
|
|
767 (@pxref{Window Configurations}).
|
|
|
768
|
|
|
769 The value returned by @code{save-excursion} is the result of the last of
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|
|
770 @var{forms}, or @code{nil} if no @var{forms} are given.
|
|
|
771
|
|
|
772 @example
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|
|
773 @group
|
|
|
774 (save-excursion
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|
|
775 @var{forms})
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|
|
776 @equiv{}
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|
|
777 (let ((old-buf (current-buffer))
|
|
|
778 (old-pnt (point-marker))
|
|
|
779 (old-mark (copy-marker (mark-marker))))
|
|
|
780 (unwind-protect
|
|
|
781 (progn @var{forms})
|
|
|
782 (set-buffer old-buf)
|
|
|
783 (goto-char old-pnt)
|
|
|
784 (set-marker (mark-marker) old-mark)))
|
|
|
785 @end group
|
|
|
786 @end example
|
|
|
787 @end defspec
|
|
|
788
|
|
|
789 @defspec save-current-buffer forms@dots{}
|
|
|
790 This special form is similar to @code{save-excursion} but it only
|
|
|
791 saves and restores the current buffer.
|
|
|
792 @end defspec
|
|
|
793
|
|
|
794 @defspec save-selected-window forms@dots{}
|
|
|
795 This special form is similar to @code{save-excursion} but it saves and
|
|
|
796 restores the selected window and nothing else.
|
|
|
797 @end defspec
|
|
|
798
|
|
|
799 @node Narrowing
|
|
|
800 @section Narrowing
|
|
|
801 @cindex narrowing
|
|
|
802 @cindex restriction (in a buffer)
|
|
|
803 @cindex accessible portion (of a buffer)
|
|
|
804
|
|
|
805 @dfn{Narrowing} means limiting the text addressable by XEmacs editing
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|
|
806 commands to a limited range of characters in a buffer. The text that
|
|
|
807 remains addressable is called the @dfn{accessible portion} of the
|
|
|
808 buffer.
|
|
|
809
|
|
|
810 Narrowing is specified with two buffer positions which become the
|
|
|
811 beginning and end of the accessible portion. For most editing commands
|
|
|
812 and most Emacs primitives, these positions replace the values of the
|
|
|
813 beginning and end of the buffer. While narrowing is in effect, no text
|
|
|
814 outside the accessible portion is displayed, and point cannot move
|
|
|
815 outside the accessible portion.
|
|
|
816
|
|
|
817 Values such as positions or line numbers, which usually count from the
|
|
|
818 beginning of the buffer, do so despite narrowing, but the functions
|
|
|
819 which use them refuse to operate on text that is inaccessible.
|
|
|
820
|
|
|
821 The commands for saving buffers are unaffected by narrowing; they save
|
|
|
822 the entire buffer regardless of any narrowing.
|
|
|
823
|
|
|
824 @deffn Command narrow-to-region start end &optional buffer
|
|
|
825 This function sets the accessible portion of @var{buffer} to start at
|
|
|
826 @var{start} and end at @var{end}. Both arguments should be character
|
|
|
827 positions. @var{buffer} defaults to the current buffer if omitted.
|
|
|
828
|
|
|
829 In an interactive call, @var{start} and @var{end} are set to the bounds
|
|
|
830 of the current region (point and the mark, with the smallest first).
|
|
|
831 @end deffn
|
|
|
832
|
|
|
833 @deffn Command narrow-to-page &optional move-count
|
|
|
834 This function sets the accessible portion of the current buffer to
|
|
|
835 include just the current page. An optional first argument
|
|
|
836 @var{move-count} non-@code{nil} means to move forward or backward by
|
|
|
837 @var{move-count} pages and then narrow. The variable
|
|
|
838 @code{page-delimiter} specifies where pages start and end
|
|
|
839 (@pxref{Standard Regexps}).
|
|
|
840
|
|
|
841 In an interactive call, @var{move-count} is set to the numeric prefix
|
|
|
842 argument.
|
|
|
843 @end deffn
|
|
|
844
|
|
|
845 @deffn Command widen &optional buffer
|
|
|
846 @cindex widening
|
|
|
847 This function cancels any narrowing in @var{buffer}, so that the
|
|
|
848 entire contents are accessible. This is called @dfn{widening}.
|
|
|
849 It is equivalent to the following expression:
|
|
|
850
|
|
|
851 @example
|
|
|
852 (narrow-to-region 1 (1+ (buffer-size)))
|
|
|
853 @end example
|
|
|
854
|
|
|
855 @var{buffer} defaults to the current buffer if omitted.
|
|
|
856 @end deffn
|
|
|
857
|
|
|
858 @defspec save-restriction body@dots{}
|
|
|
859 This special form saves the current bounds of the accessible portion,
|
|
|
860 evaluates the @var{body} forms, and finally restores the saved bounds,
|
|
|
861 thus restoring the same state of narrowing (or absence thereof) formerly
|
|
|
862 in effect. The state of narrowing is restored even in the event of an
|
|
|
863 abnormal exit via @code{throw} or error (@pxref{Nonlocal Exits}).
|
|
|
864 Therefore, this construct is a clean way to narrow a buffer temporarily.
|
|
|
865
|
|
|
866 The value returned by @code{save-restriction} is that returned by the
|
|
|
867 last form in @var{body}, or @code{nil} if no body forms were given.
|
|
|
868
|
|
|
869 @c Wordy to avoid overfull hbox. --rjc 16mar92
|
|
|
870 @strong{Caution:} it is easy to make a mistake when using the
|
|
|
871 @code{save-restriction} construct. Read the entire description here
|
|
|
872 before you try it.
|
|
|
873
|
|
|
874 If @var{body} changes the current buffer, @code{save-restriction} still
|
|
|
875 restores the restrictions on the original buffer (the buffer whose
|
|
|
876 restructions it saved from), but it does not restore the identity of the
|
|
|
877 current buffer.
|
|
|
878
|
|
|
879 @code{save-restriction} does @emph{not} restore point and the mark; use
|
|
|
880 @code{save-excursion} for that. If you use both @code{save-restriction}
|
|
|
881 and @code{save-excursion} together, @code{save-excursion} should come
|
|
|
882 first (on the outside). Otherwise, the old point value would be
|
|
|
883 restored with temporary narrowing still in effect. If the old point
|
|
|
884 value were outside the limits of the temporary narrowing, this would
|
|
|
885 fail to restore it accurately.
|
|
|
886
|
|
|
887 The @code{save-restriction} special form records the values of the
|
|
|
888 beginning and end of the accessible portion as distances from the
|
|
|
889 beginning and end of the buffer. In other words, it records the amount
|
|
|
890 of inaccessible text before and after the accessible portion.
|
|
|
891
|
|
|
892 This method yields correct results if @var{body} does further narrowing.
|
|
|
893 However, @code{save-restriction} can become confused if the body widens
|
|
|
894 and then make changes outside the range of the saved narrowing. When
|
|
|
895 this is what you want to do, @code{save-restriction} is not the right
|
|
|
896 tool for the job. Here is what you must use instead:
|
|
|
897
|
|
|
898 @example
|
|
|
899 @group
|
|
|
900 (let ((beg (point-min-marker))
|
|
|
901 (end (point-max-marker)))
|
|
|
902 (unwind-protect
|
|
|
903 (progn @var{body})
|
|
|
904 (save-excursion
|
|
|
905 (set-buffer (marker-buffer beg))
|
|
|
906 (narrow-to-region beg end))))
|
|
|
907 @end group
|
|
|
908 @end example
|
|
|
909
|
|
|
910 Here is a simple example of correct use of @code{save-restriction}:
|
|
|
911
|
|
|
912 @example
|
|
|
913 @group
|
|
|
914 ---------- Buffer: foo ----------
|
|
|
915 This is the contents of foo
|
|
|
916 This is the contents of foo
|
|
|
917 This is the contents of foo@point{}
|
|
|
918 ---------- Buffer: foo ----------
|
|
|
919 @end group
|
|
|
920
|
|
|
921 @group
|
|
|
922 (save-excursion
|
|
|
923 (save-restriction
|
|
|
924 (goto-char 1)
|
|
|
925 (forward-line 2)
|
|
|
926 (narrow-to-region 1 (point))
|
|
|
927 (goto-char (point-min))
|
|
|
928 (replace-string "foo" "bar")))
|
|
|
929
|
|
|
930 ---------- Buffer: foo ----------
|
|
|
931 This is the contents of bar
|
|
|
932 This is the contents of bar
|
|
|
933 This is the contents of foo@point{}
|
|
|
934 ---------- Buffer: foo ----------
|
|
|
935 @end group
|
|
|
936 @end example
|
|
|
937 @end defspec
|
