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1
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444
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2 @node Running, Abbrevs, Programs, Top
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428
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3 @chapter Compiling and Testing Programs
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4
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5 The previous chapter discusses the Emacs commands that are useful for
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6 making changes in programs. This chapter deals with commands that assist
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7 in the larger process of developing and maintaining programs.
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8
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9 @menu
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10 * Compilation:: Compiling programs in languages other than Lisp
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11 (C, Pascal, etc.)
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12 * Modes: Lisp Modes. Various modes for editing Lisp programs, with
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13 different facilities for running the Lisp programs.
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14 * Libraries: Lisp Libraries. Creating Lisp programs to run in Emacs.
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15 * Eval: Lisp Eval. Executing a single Lisp expression in Emacs.
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16 * Debug: Lisp Debug. Debugging Lisp programs running in Emacs.
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17 * Interaction: Lisp Interaction. Executing Lisp in an Emacs buffer.
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18 * External Lisp:: Communicating through Emacs with a separate Lisp.
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19 @end menu
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20
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21 @node Compilation, Lisp Modes, Running, Running
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22 @section Running ``make'', or Compilers Generally
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23 @cindex inferior process
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24 @cindex make
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25 @cindex compilation errors
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26 @cindex error log
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27
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28 Emacs can run compilers for non-interactive languages like C and
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29 Fortran as inferior processes, feeding the error log into an Emacs buffer.
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30 It can also parse the error messages and visit the files in which errors
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31 are found, moving point to the line where the error occurred.
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32
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33 @table @kbd
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34 @item M-x compile
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35 Run a compiler asynchronously under Emacs, with error messages to
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36 @samp{*compilation*} buffer.
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37 @item M-x grep
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38 Run @code{grep} asynchronously under Emacs, with matching lines
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39 listed in the buffer named @samp{*compilation*}.
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40 @item M-x kill-compilation
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41 Kill the process made by the @code{M-x compile} command.
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42 @item M-x kill-grep
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43 Kill the running compilation or @code{grep} subprocess.
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44 @item C-x `
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45 Visit the next compiler error message or @code{grep} match.
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46 @end table
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47
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48 @findex compile
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49 To run @code{make} or another compiler, type @kbd{M-x compile}. This
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50 command reads a shell command line using the minibuffer, then executes
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51 the specified command line in an inferior shell with output going to the
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52 buffer named @samp{*compilation*}. By default, the current buffer's
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53 default directory is used as the working directory for the execution of
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54 the command; therefore, the makefile comes from this directory.
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55
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56 @vindex compile-command
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57 When the shell command line is read, the minibuffer appears containing a
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58 default command line (the command you used the last time you typed
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59 @kbd{M-x compile}). If you type just @key{RET}, the same command line is used
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60 again. The first @kbd{M-x compile} provides @code{make -k} as the default.
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61 The default is taken from the variable @code{compile-command}; if the
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62 appropriate compilation command for a file is something other than
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63 @code{make -k}, it can be useful to have the file specify a local value for
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64 @code{compile-command} (@pxref{File Variables}).
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65
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66 @cindex compiling files
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67 When you start a compilation, the buffer @samp{*compilation*} is
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68 displayed in another window but not selected. Its mode line displays
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69 the word @samp{run} or @samp{exit} in the parentheses to tell you whether
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70 compilation is finished. You do not have to keep this buffer visible;
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71 compilation continues in any case.
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72
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73 @findex kill-compilation
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444
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74 To kill the compilation process, type @kbd{M-x kill-compilation}. The mode
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428
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75 line of the @samp{*compilation*} buffer changes to say @samp{signal}
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76 instead of @samp{run}. Starting a new compilation also kills any
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77 running compilation, as only one can occur at any time. Starting a new
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78 compilation prompts for confirmation before actually killing a
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79 compilation that is running.@refill
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80
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81 @kindex C-x `
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82 @findex next-error
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83 To parse the compiler error messages, type @kbd{C-x `}
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84 (@code{next-error}). The character following @kbd{C-x} is the grave
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85 accent, not the single quote. The command displays the buffer
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86 @samp{*compilation*} in one window and the buffer in which the next
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87 error occurred in another window. Point in that buffer is moved to the
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88 line where the error was found. The corresponding error message is
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89 scrolled to the top of the window in which @samp{*compilation*} is
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90 displayed.
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91
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92 The first time you use @kbd{C-x `} after the start of a compilation, it
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93 parses all the error messages, visits all the files that have error
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94 messages, and creates markers pointing at the lines the error messages
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95 refer to. It then moves to the first error message location. Subsequent
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96 uses of @kbd{C-x `} advance down the data set up by the first use. When
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97 the preparsed error messages are exhausted, the next @kbd{C-x `} checks for
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98 any more error messages that have come in; this is useful if you start
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99 editing compiler errors while compilation is still going on. If no
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100 additional error messages have come in, @kbd{C-x `} reports an error.
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101
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102 @kbd{C-u C-x `} discards the preparsed error message data and parses the
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103 @samp{*compilation*} buffer again, then displays the first error.
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104 This way, you can process the same set of errors again.
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105
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106 Instead of running a compiler, you can run @code{grep} and see the
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107 lines on which matches were found. To do this, type @kbd{M-x grep} with
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108 an argument line that contains the same arguments you would give to
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109 @code{grep}: a @code{grep}-style regexp (usually in single quotes to
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110 quote the shell's special characters) followed by filenames, which may
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111 use wildcard characters. The output from @code{grep} goes in the
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112 @samp{*compilation*} buffer. You can use @kbd{C-x `} to find the lines that
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113 match as if they were compilation errors.
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114
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115 Note: a shell is used to run the compile command, but the shell is not
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116 run in interactive mode. In particular, this means that the shell starts
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117 up with no prompt. If you find your usual shell prompt making an
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118 unsightly appearance in the @samp{*compilation*} buffer, it means you
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119 have made a mistake in your shell's initialization file (@file{.cshrc}
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120 or @file{.shrc} or @dots{}) by setting the prompt unconditionally. The
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121 shell initialization file should set the prompt only if there already is
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122 a prompt. Here's how to do it in @code{csh}:
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123
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124 @example
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125 if ($?prompt) set prompt = ...
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126 @end example
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127
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128 @node Lisp Modes, Lisp Libraries, Compilation, Running
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129 @section Major Modes for Lisp
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130
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131 Emacs has four different major modes for Lisp. They are the same in
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132 terms of editing commands, but differ in the commands for executing Lisp
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133 expressions.
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134
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135 @table @asis
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136 @item Emacs-Lisp mode
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137 The mode for editing source files of programs to run in Emacs Lisp.
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138 This mode defines @kbd{C-M-x} to evaluate the current defun.
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139 @xref{Lisp Libraries}.
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140 @item Lisp Interaction mode
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141 The mode for an interactive session with Emacs Lisp. It defines
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142 @key{LFD} to evaluate the sexp before point and insert its value in the
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143 buffer. @xref{Lisp Interaction}.
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144 @item Lisp mode
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145 The mode for editing source files of programs that run in other dialects
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146 of Lisp than Emacs Lisp. This mode defines @kbd{C-M-x} to send the
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147 current defun to an inferior Lisp process. @xref{External Lisp}.
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148 @item Inferior Lisp mode
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149 The mode for an interactive session with an inferior Lisp process.
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150 This mode combines the special features of Lisp mode and Shell mode
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151 (@pxref{Shell Mode}).
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152 @item Scheme mode
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153 Like Lisp mode but for Scheme programs.
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154 @item Inferior Scheme mode
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155 The mode for an interactive session with an inferior Scheme process.
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156 @end table
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157
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158 @node Lisp Libraries, Lisp Eval, Lisp Modes, Running
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159 @section Libraries of Lisp Code for Emacs
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160 @cindex libraries
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161 @cindex loading Lisp code
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162
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163 Lisp code for Emacs editing commands is stored in files whose names
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164 conventionally end in @file{.el}. This ending tells Emacs to edit them in
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165 Emacs-Lisp mode (@pxref{Lisp Modes}).
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166
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167 @menu
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168 * Loading:: Loading libraries of Lisp code into Emacs for use.
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169 * Compiling Libraries:: Compiling a library makes it load and run faster.
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170 * Mocklisp:: Converting Mocklisp to Lisp so XEmacs can run it.
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171 @end menu
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172
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173 @node Loading, Compiling Libraries, Lisp Libraries, Lisp Libraries
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174 @subsection Loading Libraries
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175
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176 @table @kbd
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177 @item M-x load-file @var{file}
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178 Load the file @var{file} of Lisp code.
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179 @item M-x load-library @var{library}
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180 Load the library named @var{library}.
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181 @item M-x locate-library @var{library} &optional @var{nosuffix}
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182 Show the full path name of Emacs library @var{library}.
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183 @end table
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184
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185 @findex load-file
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186 To execute a file of Emacs Lisp, use @kbd{M-x load-file}. This
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187 command reads the file name you provide in the minibuffer, then executes
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188 the contents of that file as Lisp code. It is not necessary to visit
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189 the file first; in fact, this command reads the file as found on
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190 disk, not the text in an Emacs buffer.
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191
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192 @findex load
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193 @findex load-library
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194 Once a file of Lisp code is installed in the Emacs Lisp library
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195 directories, users can load it using @kbd{M-x load-library}. Programs can
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196 load it by calling @code{load-library}, or with @code{load}, a more primitive
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197 function that is similar but accepts some additional arguments.
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198
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199 @kbd{M-x load-library} differs from @kbd{M-x load-file} in that it
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200 searches a sequence of directories and tries three file names in each
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201 directory. The three names are: first, the specified name with @file{.elc}
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202 appended; second, the name with @file{.el} appended; third, the specified
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203 name alone. A @file{.elc} file would be the result of compiling the Lisp
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204 file into byte code; if possible, it is loaded in preference to the Lisp
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205 file itself because the compiled file loads and runs faster.
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206
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207 @cindex loading libraries
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208 Because the argument to @code{load-library} is usually not in itself
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209 a valid file name, file name completion is not available. In fact, when
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210 using this command, you usually do not know exactly what file name
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211 will be used.
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212
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213 @vindex load-path
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214 The sequence of directories searched by @kbd{M-x load-library} is
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215 specified by the variable @code{load-path}, a list of strings that are
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216 directory names. The elements of this list may not begin with "@samp{~}",
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217 so you must call @code{expand-file-name} on them before adding them to
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218 the list. The default value of the list contains the directory where
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219 the Lisp code for Emacs itself is stored. If you have libraries of your
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220 own, put them in a single directory and add that directory to
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221 @code{load-path}. @code{nil} in this list stands for the current
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222 default directory, but it is probably not a good idea to put @code{nil}
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223 in the list. If you start wishing that @code{nil} were in the list, you
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224 should probably use @kbd{M-x load-file} for this case.
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225
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226 The variable is initialized by the @b{EMACSLOADPATH} environment
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227 variable. If no value is specified, the variable takes the default value
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228 specified in the file @file{paths.h} when Emacs was built. If a path
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229 isn't specified in @file{paths.h}, a default value is obtained from the
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230 file system, near the directory in which the Emacs executable resides.
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231
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232 @findex locate-library
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233 Like @kbd{M-x load-library}, @kbd{M-x locate-library} searches the
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234 directories in @code{load-path} to find the file that @kbd{M-x load-library}
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235 would load. If the optional second argument @var{nosuffix} is
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236 non-@code{nil}, the suffixes @file{.elc} or @file{.el} are not added to
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237 the specified name @var{library} (like calling @code{load} instead of
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238 @code{load-library}).
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239
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240 @cindex autoload
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241 You often do not have to give any command to load a library, because the
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242 commands defined in the library are set up to @dfn{autoload} that library.
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243 Running any of those commands causes @code{load} to be called to load the
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244 library; this replaces the autoload definitions with the real ones from the
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245 library.
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246
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247 If autoloading a file does not finish, either because of an error or
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248 because of a @kbd{C-g} quit, all function definitions made by the file
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249 are undone automatically. So are any calls to @code{provide}. As a
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250 consequence, the entire file is loaded a second time if you use one of
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251 the autoloadable commands again. This prevents problems when the
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252 command is no longer autoloading but is working incorrectly because the file
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253 was only partially loaded. Function definitions are undone only for
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254 autoloading; explicit calls to @code{load} do not undo anything if
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255 loading is not completed.
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256
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257 @vindex after-load-alist
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258 The variable @code{after-load-alist} takes an alist of expressions to be
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259 evaluated when particular files are loaded. Each element has the form
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260 @code{(@var{filename} forms...)}. When @code{load} is run and the filename
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261 argument is @var{filename}, the forms in the corresponding element are
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262 executed at the end of loading.
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263
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264 @var{filename} must match exactly. Normally @var{filename} is the
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265 name of a library, with no directory specified, since that is how load
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266 is normally called. An error in @code{forms} does not undo the load, but
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267 it does prevent execution of the rest of the @code{forms}.
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268
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269 @node Compiling Libraries, Mocklisp, Loading, Lisp Libraries
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270 @subsection Compiling Libraries
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271
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272 @cindex byte code
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273 Emacs Lisp code can be compiled into byte-code which loads faster,
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274 takes up less space when loaded, and executes faster.
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275
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276 @table @kbd
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277 @item M-x batch-byte-compile
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278 Run byte-compile-file on the files remaining on the command line.
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279 @item M-x byte-compile-buffer &optional @var{buffer}
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280 Byte-compile and evaluate contents of @var{buffer} (default is current
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281 buffer).
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282 @item M-x byte-compile-file
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283 Compile a file of Lisp code named @var{filename} into a file of byte code.
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284 @item M-x byte-compile-and-load-file @var{filename}
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285 Compile a file of Lisp code named @var{filename} into a file of byte
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286 code and load it.
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287 @item M-x byte-recompile-directory @var{directory}
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288 Recompile every @file{.el} file in @var{directory} that needs recompilation.
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289 @item M-x disassemble
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290 Print disassembled code for @var{object} on (optional) @var{stream}.
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291 @findex make-obsolete
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292 @item M-x make-obsolete @var{function new}
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293 Make the byte-compiler warn that @var{function} is obsolete and @var{new}
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294 should be used instead.
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295 @end table
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296
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297 @findex byte-compile-file
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298 @findex byte-compile-and-load-file
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299 @findex byte-compile-buffer
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300 @kbd{byte-compile-file} creates a byte-code compiled file from an
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301 Emacs-Lisp source file. The default argument for this function is the
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302 file visited in the current buffer. The function reads the specified
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303 file, compiles it into byte code, and writes an output file whose name
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304 is made by appending @file{c} to the input file name. Thus, the file
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305 @file{rmail.el} would be compiled into @file{rmail.elc}. To compile a
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306 file of Lisp code named @var{filename} into a file of byte code and
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307 then load it, use @code{byte-compile-and-load-file}. To compile and
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308 evaluate Lisp code in a given buffer, use @code{byte-compile-buffer}.
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309
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310 @findex byte-recompile-directory
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311 To recompile all changed Lisp files in a directory, use @kbd{M-x
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312 byte-recompile-directory}. Specify just the directory name as an argument.
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313 Each @file{.el} file that has been byte-compiled before is byte-compiled
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314 again if it has changed since the previous compilation. A numeric argument
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315 to this command tells it to offer to compile each @file{.el} file that has
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316 not been compiled yet. You must answer @kbd{y} or @kbd{n} to each
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317 offer.
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318
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319 @findex batch-byte-compile
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320 You can use the function @code{batch-byte-compile} to invoke Emacs
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321 non-interactively from the shell to do byte compilation. When you use
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322 this function, the files to be compiled are specified with command-line
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323 arguments. Use a shell command of the form:
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324
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325 @example
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326 emacs -batch -f batch-byte-compile @var{files}...
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327 @end example
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328
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329 Directory names may also be given as arguments; in that case,
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330 @code{byte-recompile-directory} is invoked on each such directory.
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331 @code{batch-byte-compile} uses all remaining command-line arguments as
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332 file or directory names, then kills the Emacs process.
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333
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334 @findex disassemble
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335 @kbd{M-x disassemble} explains the result of byte compilation. Its
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336 argument is a function name. It displays the byte-compiled code in a help
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337 window in symbolic form, one instruction per line. If the instruction
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338 refers to a variable or constant, that is shown, too.
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339
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340 @node Mocklisp,,Compiling Libraries,Lisp Libraries
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341 @subsection Converting Mocklisp to Lisp
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342
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343 @cindex mocklisp
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344 @findex convert-mocklisp-buffer
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345 XEmacs can run Mocklisp files by converting them to Emacs Lisp first.
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346 To convert a Mocklisp file, visit it and then type @kbd{M-x
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347 convert-mocklisp-buffer}. Then save the resulting buffer of Lisp file in a
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348 file whose name ends in @file{.el} and use the new file as a Lisp library.
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349
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350 You cannot currently byte-compile converted Mocklisp code.
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351 The reason is that converted Mocklisp code uses some special Lisp features
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352 to deal with Mocklisp's incompatible ideas of how arguments are evaluated
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353 and which values signify ``true'' or ``false''.
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354
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355 @node Lisp Eval, Lisp Debug, Lisp Libraries, Running
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356 @section Evaluating Emacs-Lisp Expressions
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357 @cindex Emacs-Lisp mode
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358
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359 @findex emacs-lisp-mode
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360 Lisp programs intended to be run in Emacs should be edited in
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361 Emacs-Lisp mode; this will happen automatically for file names ending in
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362 @file{.el}. By contrast, Lisp mode itself should be used for editing
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363 Lisp programs intended for other Lisp systems. Emacs-Lisp mode can be
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364 selected with the command @kbd{M-x emacs-lisp-mode}.
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365
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366 For testing of Lisp programs to run in Emacs, it is useful to be able
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367 to evaluate part of the program as it is found in the Emacs buffer. For
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368 example, if you change the text of a Lisp function definition and then
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369 evaluate the definition, Emacs installs the change for future calls to the
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370 function. Evaluation of Lisp expressions is also useful in any kind of
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371 editing task for invoking non-interactive functions (functions that are
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372 not commands).
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373
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374 @table @kbd
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375 @item M-@key{ESC}
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376 Read a Lisp expression in the minibuffer, evaluate it, and print the
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377 value in the minibuffer (@code{eval-expression}).
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378 @item C-x C-e
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379 Evaluate the Lisp expression before point, and print the value in the
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380 minibuffer (@code{eval-last-sexp}).
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381 @item C-M-x
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382 Evaluate the defun containing point or after point, and print the value in
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383 the minibuffer (@code{eval-defun}).
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384 @item M-x eval-region
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385 Evaluate all the Lisp expressions in the region.
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386 @item M-x eval-current-buffer
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387 Evaluate all the Lisp expressions in the buffer.
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388 @end table
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389
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390 @kindex M-ESC
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391 @findex eval-expression
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392 @kbd{M-@key{ESC}} (@code{eval-expression}) is the most basic command
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393 for evaluating a Lisp expression interactively. It reads the expression
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394 using the minibuffer, so you can execute any expression on a buffer
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395 regardless of what the buffer contains. When evaluation is complete,
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396 the current buffer is once again the buffer that was current when
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397 @kbd{M-@key{ESC}} was typed.
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398
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399 @kbd{M-@key{ESC}} can easily confuse users, especially on keyboards
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400 with autorepeat, where it can result from holding down the @key{ESC} key
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401 for too long. Therefore, @code{eval-expression} is normally a disabled
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402 command. Attempting to use this command asks for confirmation and gives
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403 you the option of enabling it; once you enable the command, you are no
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404 longer required to confirm. @xref{Disabling}.@refill
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405
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406 @kindex C-M-x
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407 @findex eval-defun
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408 In Emacs-Lisp mode, the key @kbd{C-M-x} is bound to the function
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409 @code{eval-defun}, which parses the defun containing point or following point
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410 as a Lisp expression and evaluates it. The value is printed in the echo
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411 area. This command is convenient for installing in the Lisp environment
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412 changes that you have just made in the text of a function definition.
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413
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414 @kindex C-x C-e
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415 @findex eval-last-sexp
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416 The command @kbd{C-x C-e} (@code{eval-last-sexp}) performs a similar job
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417 but is available in all major modes, not just Emacs-Lisp mode. It finds
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418 the sexp before point, reads it as a Lisp expression, evaluates it, and
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419 prints the value in the echo area. It is sometimes useful to type in an
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420 expression and then, with point still after it, type @kbd{C-x C-e}.
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421
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422 If @kbd{C-M-x} or @kbd{C-x C-e} are given a numeric argument, they
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423 print the value by inserting it into the current buffer at point, rather
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424 than in the echo area. The argument value does not matter.
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425
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426 @findex eval-region
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427 @findex eval-current-buffer
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428 The most general command for evaluating Lisp expressions from a buffer
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429 is @code{eval-region}. @kbd{M-x eval-region} parses the text of the
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430 region as one or more Lisp expressions, evaluating them one by one.
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431 @kbd{M-x eval-current-buffer} is similar, but it evaluates the entire
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432 buffer. This is a reasonable way to install the contents of a file of
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433 Lisp code that you are just ready to test. After finding and fixing a
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434 bug, use @kbd{C-M-x} on each function that you change, to keep the Lisp
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435 world in step with the source file.
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436
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437 @node Lisp Debug, Lisp Interaction, Lisp Eval, Running
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438 @section The Emacs-Lisp Debugger
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439 @cindex debugger
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440
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441 @vindex debug-on-error
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442 @vindex debug-on-quit
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443 XEmacs contains a debugger for Lisp programs executing inside it.
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444 This debugger is normally not used; many commands frequently get Lisp
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445 errors when invoked in inappropriate contexts (such as @kbd{C-f} at the
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446 end of the buffer) and it would be unpleasant to enter a special
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447 debugging mode in this case. When you want to make Lisp errors invoke
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448 the debugger, you must set the variable @code{debug-on-error} to
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449 non-@code{nil}. Quitting with @kbd{C-g} is not considered an error, and
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450 @code{debug-on-error} has no effect on the handling of @kbd{C-g}.
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451 However, if you set @code{debug-on-quit} to be non-@code{nil}, @kbd{C-g} will
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452 invoke the debugger. This can be useful for debugging an infinite loop;
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453 type @kbd{C-g} once the loop has had time to reach its steady state.
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454 @code{debug-on-quit} has no effect on errors.@refill
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455
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456 @findex debug-on-entry
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457 @findex cancel-debug-on-entry
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458 @findex debug
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459 You can make Emacs enter the debugger when a specified function
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460 is called or at a particular place in Lisp code. Use @kbd{M-x
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461 debug-on-entry} with argument @var{fun-name} to have Emacs enter the
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462 debugger as soon as @var{fun-name} is called. Use
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463 @kbd{M-x cancel-debug-on-entry} to make the function stop entering the
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464 debugger when called. (Redefining the function also does this.) To enter
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465 the debugger from some other place in Lisp code, you must insert the
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466 expression @code{(debug)} there and install the changed code with
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467 @kbd{C-M-x}. @xref{Lisp Eval}.@refill
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468
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469 When the debugger is entered, it displays the previously selected buffer
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470 in one window and a buffer named @samp{*Backtrace*} in another window. The
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471 backtrace buffer contains one line for each level of Lisp function
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472 execution currently going on. At the beginning of the buffer is a message
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473 describing the reason that the debugger was invoked, for example, an
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474 error message if it was invoked due to an error.
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475
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476 The backtrace buffer is read-only and is in Backtrace mode, a special
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477 major mode in which letters are defined as debugger commands. The
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478 usual Emacs editing commands are available; you can switch windows to
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479 examine the buffer that was being edited at the time of the error, and
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480 you can switch buffers, visit files, and perform any other editing
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481 operations. However, the debugger is a recursive editing level
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482 (@pxref{Recursive Edit}); it is a good idea to return to the backtrace
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442
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483 buffer and explicitly exit the debugger when you don't want to use it any
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|
428
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484 more. Exiting the debugger kills the backtrace buffer.
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485
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486 @cindex current stack frame
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487 The contents of the backtrace buffer show you the functions that are
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488 executing and the arguments that were given to them. It also allows you
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489 to specify a stack frame by moving point to the line describing that
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490 frame. The frame whose line point is on is considered the @dfn{current
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491 frame}. Some of the debugger commands operate on the current frame.
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492 Debugger commands are mainly used for stepping through code one
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493 expression at a time. Here is a list of them:
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494
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|
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495 @table @kbd
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496 @item c
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497 Exit the debugger and continue execution. In most cases, execution of
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498 the program continues as if the debugger had never been entered (aside
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499 from the effect of any variables or data structures you may have changed
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500 while inside the debugger). This includes entry to the debugger due to
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501 function entry or exit, explicit invocation, and quitting or certain
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502 errors. Most errors cannot be continued; trying to continue an error usually
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503 causes the same error to occur again.
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504 @item d
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505 Continue execution, but enter the debugger the next time a Lisp
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506 function is called. This allows you to step through the
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507 subexpressions of an expression, and see what the subexpressions do and
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508 what values they compute.
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509
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510 When you enter the debugger this way, Emacs flags the stack frame for the
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511 function call from which you entered. The same function is then called
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512 when you exit the frame. To cancel this flag, use @kbd{u}.
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|
|
513 @item b
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514 Set up to enter the debugger when the current frame is exited. Frames
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515 that invoke the debugger on exit are flagged with stars.
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|
|
516 @item u
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|
|
517 Don't enter the debugger when the current frame is exited. This
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518 cancels a @kbd{b} command on a frame.
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519 @item e
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|
|
520 Read a Lisp expression in the minibuffer, evaluate it, and print the
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|
|
521 value in the echo area. This is equivalent to the command @kbd{M-@key{ESC}},
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|
522 except that @kbd{e} is not normally disabled like @kbd{M-@key{ESC}}.
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|
|
523 @item q
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|
|
524 Terminate the program being debugged; return to top-level Emacs
|
|
|
525 command execution.
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|
|
526
|
|
|
527 If the debugger was entered due to a @kbd{C-g} but you really want
|
|
|
528 to quit, not to debug, use the @kbd{q} command.
|
|
|
529 @item r
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|
|
530 Return a value from the debugger. The value is computed by reading an
|
|
|
531 expression with the minibuffer and evaluating it.
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|
|
532
|
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|
533 The value returned by the debugger makes a difference when the debugger
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|
|
534 was invoked due to exit from a Lisp call frame (as requested with @kbd{b});
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535 then the value specified in the @kbd{r} command is used as the value of
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|
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536 that frame.
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|
|
537
|
|
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538 The debugger's return value also matters with many errors. For example,
|
|
|
539 @code{wrong-type-argument} errors will use the debugger's return value
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|
|
540 instead of the invalid argument; @code{no-catch} errors will use the
|
|
|
541 debugger value as a throw tag instead of the tag that was not found.
|
|
|
542 If an error was signaled by calling the Lisp function @code{signal},
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|
|
543 the debugger's return value is returned as the value of @code{signal}.
|
|
|
544 @end table
|
|
|
545
|
|
|
546 @node Lisp Interaction, External Lisp, Lisp Debug, Running
|
|
|
547 @section Lisp Interaction Buffers
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|
|
548
|
|
|
549 The buffer @samp{*scratch*}, which is selected when Emacs starts up, is
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|
550 provided for evaluating Lisp expressions interactively inside Emacs. Both
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551 the expressions you evaluate and their output goes in the buffer.
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552
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|
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553 The @samp{*scratch*} buffer's major mode is Lisp Interaction mode, which
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|
|
554 is the same as Emacs-Lisp mode except for one command, @key{LFD}. In
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555 Emacs-Lisp mode, @key{LFD} is an indentation command. In Lisp
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|
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556 Interaction mode, @key{LFD} is bound to @code{eval-print-last-sexp}. This
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|
|
557 function reads the Lisp expression before point, evaluates it, and inserts
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|
|
558 the value in printed representation before point.
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|
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559
|
|
|
560 The way to use the @samp{*scratch*} buffer is to insert Lisp
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|
|
561 expressions at the end, ending each one with @key{LFD} so that it will
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|
|
562 be evaluated. The result is a complete typescript of the expressions
|
|
|
563 you have evaluated and their values.
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|
|
564
|
|
|
565 @findex lisp-interaction-mode
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|
|
566 The rationale for this feature is that Emacs must have a buffer when it
|
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|
567 starts up, but that buffer is not useful for editing files since a new
|
|
|
568 buffer is made for every file that you visit. The Lisp interpreter
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|
|
569 typescript is the most useful thing I can think of for the initial buffer
|
|
|
570 to do. @kbd{M-x lisp-interaction-mode} will put any buffer in Lisp
|
|
|
571 Interaction mode.
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|
|
572
|
|
|
573 @node External Lisp,, Lisp Interaction, Running
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|
|
574 @section Running an External Lisp
|
|
|
575
|
|
|
576 Emacs has facilities for running programs in other Lisp systems. You can
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|
|
577 run a Lisp process as an inferior of Emacs, and pass expressions to it to
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|
|
578 be evaluated. You can also pass changed function definitions directly from
|
|
|
579 the Emacs buffers in which you edit the Lisp programs to the inferior Lisp
|
|
|
580 process.
|
|
|
581
|
|
|
582 @findex run-lisp
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|
|
583 To run an inferior Lisp process, type @kbd{M-x run-lisp}. This runs the
|
|
|
584 program named @code{lisp}, the same program you would run by typing
|
|
|
585 @code{lisp} as a shell command, with both input and output going through an
|
|
|
586 Emacs buffer named @samp{*lisp*}. In other words, any ``terminal output''
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|
|
587 from Lisp will go into the buffer, advancing point, and any ``terminal
|
|
|
588 input'' for Lisp comes from text in the buffer. To give input to Lisp, go
|
|
|
589 to the end of the buffer and type the input, terminated by @key{RET}. The
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|
|
590 @samp{*lisp*} buffer is in Inferior Lisp mode, which has all the
|
|
|
591 special characteristics of Lisp mode and Shell mode (@pxref{Shell Mode}).
|
|
|
592
|
|
|
593 @findex lisp-mode
|
|
|
594 Use Lisp mode to run the source files of programs in external Lisps.
|
|
|
595 You can select this mode with @kbd{M-x lisp-mode}. It is used automatically
|
|
|
596 for files whose names end in @file{.l} or @file{.lisp}, as most Lisp
|
|
|
597 systems usually expect.
|
|
|
598
|
|
|
599 @kindex C-M-x
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|
|
600 @findex lisp-send-defun
|
|
|
601 When you edit a function in a Lisp program you are running, the easiest
|
|
|
602 way to send the changed definition to the inferior Lisp process is the key
|
|
|
603 @kbd{C-M-x}. In Lisp mode, this key runs the function @code{lisp-send-defun},
|
|
|
604 which finds the defun around or following point and sends it as input to
|
|
|
605 the Lisp process. (Emacs can send input to any inferior process regardless
|
|
|
606 of what buffer is current.)
|
|
|
607
|
|
|
608 Contrast the meanings of @kbd{C-M-x} in Lisp mode (for editing programs
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|
|
609 to be run in another Lisp system) and Emacs-Lisp mode (for editing Lisp
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|
|
610 programs to be run in Emacs): in both modes it has the effect of installing
|
|
|
611 the function definition that point is in, but the way of doing so is
|
|
|
612 different according to where the relevant Lisp environment is found.
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|
|
613 @xref{Lisp Modes}.
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