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doc/devel/source/conversions.fr.tm

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<TeXmacs|1.0.1.10>
<style|tmdoc>
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<expand|tmdoc-title|Convertisseurs vers d'autres formats de données>
Currently, we have implemented imperfect converters between <apply|TeXmacs>
and <apply|LaTeX> and from html to <apply|TeXmacs>. We hope that someone
else will be willing to write better converters from scratch. This chapter
has been included in order to give some recommendations in that direction
based on our experience from the implementation of the actual conversion
programs. We also recommend to take a look at the current implementations
in the directory <verbatim|Convert>.
<section|Parsing extern data formats>
In order to write a converter from <apply|LaTeX> html, xml, etc. to
<apply|TeXmacs>, a good first step is to write a parser for the extern data
format. For html, xml, etc. this should be rather easy, but for
<apply|LaTeX>, you will probably need to be a real <apply|LaTeX> guru
(which I am not). We recommend the result of the parsing step to be a
<apply|scheme> expression (something which is regrettable not the case for
our actual converters), because this language is very well adapted for the
implementation of the actual converter.
This first step should be able to process any correct file having the
extern data format; possible incompatibilities should only come into play
during the actual conversion. In the case of <apply|LaTeX>, one should not
expand the macros and keep all macro definitions, because <apply|TeXmacs>
will be able to take advantage out of this.
<section|The actual converter>
We recommend the actual converter to proceed in several steps. Often it is
convenient to start with a rough, structural, conversion step, which is
``polished'' by a certain number of additional steps. These additional
steps may take care of some very particular layout issues which can not be
treated conveniently at the main step.
Actually, the main difficulties usually come from exceptional text, like
verbatim, and layout issues which are handled differently in the extern
data format and <apply|TeXmacs>. A good example of such a difference
between <apply|LaTeX> and <apply|TeXmacs> is the way equations or lists are
handled. Consider for instance the following paragraph:
Text before.
<\expand|equation*>
a<rsup|2>+b<rsup|2>=c<rsup|2>.
</expand>
Text after.
In <apply|LaTeX>, the equation is really seen as a part of the paragraph.
Indeed, there will not be any blank line between ``Text before'' and the
equation. However, for efficiency reasons, it is better to see the
paragraph as three paragraphs in <apply|TeXmacs>, because the lines can be
typesetted independently. Nevertheless, the equation environment will
disable the indentation of ``Text after''.
As a result of this anomaly, converted texts have to be postprocessed, so
as to insert paragraph breaks at strategic places. It should be noticed
that this step may be independent from the format which is actually being
converted and that a similar reverse step may be implemented for backward
conversions. We also notice that one needs an exhaustive list of all
similar exceptional environments for this postprocessing step. Actually, a
future version of <apply|TeXmacs> might come with an additional feature,
which permits the automatic detection of such environments. This is also
important from a semantical point of view, because one should be able to
detect that the above example logically forms only one and not three
paragraphs.
<section|Backward conversions>
Conversions from <apply|TeXmacs> to an extern data format are usually
easier to implement, because the <apply|TeXmacs> data format is
semantically rich. However, conversions to an extern data format without a
<apply|TeX>-like macro facility give rise to the problem of macro expansion
of non supported <apply|TeXmacs> functions or environments. We plan to
write a facility for this, which you will be able to use when writing a
converter from <apply|TeXmacs> to something else.
<apply|tmdoc-copyright|1998--2003|Joris van der Hoeven|Michèle Garoche>
<expand|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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<vspace*|1fn><with|font series|<quote|bold>|math font
series|<quote|bold>|1<space|2spc>Parsing extern data
formats><value|toc-dots><pageref|toc-1><vspace|0.5fn>
<vspace*|1fn><with|font series|<quote|bold>|math font
series|<quote|bold>|2<space|2spc>The actual
converter><value|toc-dots><pageref|toc-2><vspace|0.5fn>
<vspace*|1fn><with|font series|<quote|bold>|math font
series|<quote|bold>|3<space|2spc>Backward
conversions><value|toc-dots><pageref|toc-3><vspace|0.5fn>
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