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142 lines
4.7 KiB
Text
142 lines
4.7 KiB
Text
@c -*-texinfo-*-
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@c This is part of the GNU Guile Reference Manual.
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@c Copyright (C) 1996, 1997, 2000, 2001, 2002, 2003, 2004
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@c Free Software Foundation, Inc.
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@c See the file guile.texi for copying conditions.
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@page
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@node Readline Support
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@chapter Readline Support
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@c FIXME::martin: Review me!
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@cindex readline
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@cindex command line history
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Guile comes with an interface module to the readline library. This
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makes interactive use much more convenient, because of the command-line
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editing features of readline. Using @code{(ice-9 readline)}, you can
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navigate through the current input line with the cursor keys, retrieve
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older command lines from the input history and even search through the
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history entries.
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@menu
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* Loading Readline Support:: How to load readline support into Guile.
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* Readline Options:: How to modify readline's behaviour.
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@end menu
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@node Loading Readline Support
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@section Loading Readline Support
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The module is not loaded by default and so has to be loaded and
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activated explicitly. This is done with two simple lines of code:
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@findex activate-readline
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@lisp
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(use-modules (ice-9 readline))
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(activate-readline)
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@end lisp
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@c FIXME::martin: Review me!
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The first line will load the necessary code, and the second will
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activate readline's features for the REPL. If you plan to use this
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module often, you should save these to lines to your @file{.guile}
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personal startup file.
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You will notice that the REPL's behaviour changes a bit when you have
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loaded the readline module. For example, when you press Enter before
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typing in the closing parentheses of a list, you will see the
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@dfn{continuation} prompt, three dots: @code{...} This gives you a nice
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visual feedback when trying to match parentheses. To make this even
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easier, @dfn{bouncing parentheses} are implemented. That means that
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when you type in a closing parentheses, the cursor will jump to the
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corresponding opening parenthesis for a short time, making it trivial to make
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them match.
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Once the readline module is activated, all lines entered interactively
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will be stored in a history and can be recalled later using the
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cursor-up and -down keys. Readline also understands the Emacs keys for
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navigating through the command line and history.
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When you quit your Guile session by evaluating @code{(quit)} or pressing
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Ctrl-D, the history will be saved to the file @file{.guile_history} and
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read in when you start Guile for the next time. Thus you can start a
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new Guile session and still have the (probably long-winded) definition
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expressions available.
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@node Readline Options
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@section Readline Options
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@c FIXME::martin: Review me!
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@cindex readline options
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The readline interface module can be configured in several ways to
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better suit the user's needs. Configuration is done via the readline
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module's options interface, in a similar way to the evaluator and
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debugging options (@pxref{User level options interfaces}.)
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@findex readline-options
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@findex readline-enable
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@findex readline-disable
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@findex readline-set!
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Here is the list of readline options generated by typing
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@code{(readline-options 'full)} in Guile. You can also see the
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default values.
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@smalllisp
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bounce-parens 500 Time (ms) to show matching opening parenthesis (0 = off).
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history-length 200 History length.
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history-file yes Use history file.
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@end smalllisp
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The history length specifies how many input lines will be remembered.
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If the history contains that many lines and additional lines are
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entered, the oldest lines will be lost. You can switch on/off the
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usage of the history file using the following call.
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@lisp
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(readline-disable 'history)
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@end lisp
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The readline options interface can only be used @emph{after} loading
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the readline module, because it is defined in that module.
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@page
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@node Value History
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@chapter Value History
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@c FIXME::martin: Review me!
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@cindex value history
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Another module which makes command line usage more convenient is
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@code{(ice-9 history)}. This module will change the REPL so that each
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value which is evaluated and printed will be remembered under a name
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constructed from the dollar character (@code{$}) and the number of the
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evaluated expression.
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Consider an example session.
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@example
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guile> (use-modules (ice-9 history))
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guile> 1
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$1 = 1
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guile> (+ $1 $1)
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$2 = 2
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guile> (* $2 $2)
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$3 = 4
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@end example
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After loading the value history module @code{(ice-9 history)}, one
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(trivial) expression is evaluated. The result is stored into the
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variable @code{$1}. This fact is indicated by the output @code{$1 = },
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which is also caused by @code{(ice-9 history)}. In the next line, this
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variable is used two times, to produce the value @code{$2}, which in
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turn is used in the calculation for @code{$3}.
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@c Local Variables:
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@c TeX-master: "guile.texi"
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@c End:
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