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doc/devel/scheme/overview/overview-utilities.en.tm

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<TeXmacs|1.99.8>
<style|<tuple|tmdoc|old-spacing>>
<\body>
<tmdoc-title|Standard utilities>
Besides the basic concepts from the previous sections, which underly the
scheme API for <TeXmacs>, the <scheme> kernel implements several other
utilities and language extensions. In this section, we will briefly sketch
some of them on hand of examples. Further details can be found in the
chapter about <hlink|<TeXmacs> extensions to <scheme> and
utilities|../utils/scheme-utils.en.tm>.
<paragraph*|Regular expressions>
<TeXmacs> implements the routines <scm|match?> and <scm|select> for
matching regular expressions and selecting subexpressions along a \Ppath\Q.
These routines both work for the <verbatim|content> type. For instance, in
order to search all expressions of the form
<\equation*>
<frac|<with|color|brown|a>|1+<sqrt|<with|color|brown|b>>>
</equation*>
in the current buffer, where <math|<with|color|brown|a>> and
<math|<with|color|brown|b>> are general expressions, one may use the
following <scheme> command:
<\session|scheme|default>
<\input|scheme] >
(select (buffer-tree) '(:* (:match (frac :%1 (concat "1+" (sqrt
:%1))))))
</input>
</session>
<paragraph*|Dialogues>
<TeXmacs> supports several commands for interactive dialogues with the
user. For instance, when executing the following scheme command, you will
be prompted for two numbers, whose product will be displayed in the footer:
<\session|scheme|default>
<\input|Scheme] >
(user-ask "First number:"
\ \ (lambda (a)
\ \ \ \ (user-ask "Second number:"
\ \ \ \ \ \ (lambda (b)
\ \ \ \ \ \ \ \ (set-message (number-\<gtr\>string (*
(string-\<gtr\>number a)
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ (string-\<gtr\>number
b)))
\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ "product")))))
</input>
<\input|Scheme] >
\;
</input>
</session>
<paragraph*|User preferences>
When writing a plug-in, you may wish to define some new user preferences.
This can be done using the <scm|define-preferences> command, which adds a
list of user preferences, together with their default values and a
call-back routine. The call-back routine is called whenever you change the
corresponding preference. For instance:
<\scm-code>
(define-preferences
\ \ ("Gnu's hair color" "brown" notify-gnu-hair-change)
\ \ ("Snail's cruising speed" "1mm/sec" notify-Achilles))
</scm-code>
Preferences can be set, reset and read using <scm|set-preference>,
<scm|reset-preference> and <scm|get-preference>.
<paragraph*|New data formats and converters>
New data formats and converters can be declared using the
<scm|define-format> and <scm|converter> instructions. When a format can be
converted from or into <TeXmacs>, then it will automatically appear into
the <menu|File|Export> and <menu|File|Import> menus. Similarly, when a
format can be converted to <name|Postscript>, then it also becomes a valid
format for images. <TeXmacs> also attempts to combine explicitly declared
converters into new ones.
Typically, the declaration of a new format and a converter would look like:
<\scm-code>
(define-format blablah
\ \ (:name "Blablah")
\ \ (:suffix "bla"))
\;
(converter blablah-file latex-file
\ \ (:require (url-exists-in-path? "bla2tex"))
\ \ (:shell "bla2tex" from "\<gtr\>" to))
</scm-code>
<tmdoc-copyright|2005|Joris van der Hoeven>
<tmdoc-license|Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version 1.1
or any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section entitled "GNU Free
Documentation License".>
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