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<div>Hi Zdenek,<br>
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<div>On 13/04/2020, at 0:00, "Zdenek Wagner" <<a href="mailto:zdenek.wagner@gmail.com">zdenek.wagner@gmail.com</a>> wrote:<br>
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<div>Hi all,</div>
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<div>This can be done with \let and \def, not with \newcommand:</div>
<div><br>
</div>
<div>\let\savedLabel\label</div>
<div>\def\label#1{Do something with #1 \SavedLabel{#1}}</div>
<div><br>
</div>
<div>The second line could be replaced with</div>
<div>\renewcommand*\label[1]{Do something with #1 \SavedLabel{#1}}</div>
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<div><br>
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<div>This idea can be extended somewhat.</div>
<div><br>
</div>
<div>\makeatletter</div>
<div>\def\MY@label#1{<span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">Do something
with #1 \LTX@label{#1}}</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">\AtBeginDocument{</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); "> \let\LTX@label\label</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); "> \let\label\MY@label</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">}</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">\makeatother</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); "><br>
</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">This way you retain pointers
to both your own version and the original, </span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">so can change between them if
necessary, within different parts of your</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">document, or within specially
tailored environments.</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); "><br>
</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">Delaying the \let rebindings
using \AtBeginDocument means that it will still work</span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">if some other package (such as
hyperref ) makes its own changes, </span></div>
<div><span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.292969); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">which you also want to incorporate.</span></div>
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<div>\providecommand is useful if you assume that a definition exist but you want to provide a default definition.</div>
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<div>Sure.</div>
<div>It is particularly useful when devising templates that will be filled with information </div>
<div>provided by a database, and command-line shell software that automates </div>
<div>calls to TeX or LaTeX or other engine.</div>
<div><br>
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<div>latex '\def\name{client name} ... \input{mytemplate.tex}'</div>
<div><br>
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<div>where mytemplate.tex is the main LaTeX source, having</div>
<div> \providecommand{\name}{some default}</div>
<div>and similarly for all the variable data fields.</div>
<div><br>
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<div>I use this kind of setup to automate personalised assignment cover-sheets,</div>
<div>generated online in response to student requests from a web page.</div>
<div>Sometimes the full question sheet is done this way,</div>
<div>with versions personalized, or randomized, <span class="Apple-style-span" style="-webkit-tap-highlight-color: rgba(26, 26, 26, 0.296875); -webkit-composition-fill-color: rgba(175, 192, 227, 0.230469); -webkit-composition-frame-color: rgba(77, 128, 180, 0.230469); ">based
upon student ID numbers.</span></div>
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<div>The newcommand family is useful because it offers a default first argument but if you use arguments with the newcommand family, use always the star version so that the macro is not \long. If you forget a right brace after an argument, you will get an error
message at the end of a paragraph but without the star you get an error message at the end of a file hence it is difficult the source of the error.</div>
<div><br>
</div>
<div>Construct \csname scenename\endcsname expands to the contents of \scenename if already defined or is defined to be identical with \relax if not yet defined. When checking existence of definition, LaTeX does the following:</div>
<div><br>
</div>
<div>\expandafter\ifx\csname scenename\endcsname\relax</div>
<div> code for \scenename not yet defined</div>
<div>\else</div>
<div> code for \scenename already defined</div>
<div>\fi</div>
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<div>With \csname you can test for all kinds of things,</div>
<div>and even adjust macros like \begin and \end to patch in extra coding</div>
<div>for specific environments, whether a package is loaded or not.</div>
<div><br>
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<div>The possibilities are endless.</div>
<div><br>
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<div>Cheers.</div>
<div>Stay safe.</div>
<div><br>
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<div> Ross</div>
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<div>Of course, the whole \else part can be omitted if you have nothing to put there.</div>
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<div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature">Zdeněk Wagner<br>
<a href="https://protect-au.mimecast.com/s/QcrSCnx1Z5UgvO8wS9Msu9?domain=ttsm.icpf.cas.cz" target="_blank">http://ttsm.icpf.cas.cz/team/wagner.shtml</a><br>
<a href="https://protect-au.mimecast.com/s/fkdBCoV1Y2S5EqO9HzWPDx?domain=icebearsoft.euweb.cz" target="_blank">http://icebearsoft.euweb.cz</a></div>
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<div dir="ltr" class="gmail_attr">ne 12. 4. 2020 v 12:49 odesílatel Ross Moore <<a href="mailto:ross.moore@mq.edu.au">ross.moore@mq.edu.au</a>> napsal:<br>
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<div style="overflow-wrap: break-word;">Hi Phil, Zdeněk and others.
<div><br>
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<div>On 12 Apr 2020, at 7:46 pm, Philip Taylor <<a href="mailto:P.Taylor@Hellenic-Institute.Uk" target="_blank">P.Taylor@Hellenic-Institute.Uk</a>> wrote:</div>
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<div>Zdeněk Wagner wrote:<br>
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<pre>I would not do it. Of course, you cannot use \renewcommand because
\scenename is not used in any *.ldf. You could use \def\scenename{दरश्य} […]
</pre>
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<div>LaTeX has \providecommand with the same syntax as \newcommand and \renewcommand .</div>
<div><br>
</div>
<div>It makes the definition *only* if the c-s is not already known.</div>
<div>This means that you can always use:</div>
<div><br>
</div>
<div> \providecommand\mycs{}</div>
<div> \renewcommand\mycs{ what I really want }</div>
<div><br>
</div>
<div>to get around such issues.</div>
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<br>
A thought — if \scenename is not known at the point that the last line of [gloss-]marathi.ldf is read, would there be any point in using \def \scenename {दरश्य}, since such definition would either get over-ridden by whatever subsequent definition of \scename
is causing the problem (\def, \renewcommand), or would prevent a subsequent \newcommand from working as \scenename would already be defined. Is this not the case (he asked, as someone who barely understands anything that LaTeX does ...) ?<br>
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<div>There is always a way to get what you want,</div>
<div>whether using Plain TeX or LaTeX or whatever other high-level macro structures.</div>
<div><br>
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<div>Thus the important thing is how to make it resistant to updates, as Zdeněk said.</div>
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<i>Philip Taylor</i><br>
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Hope this helps.
<div>Stay safe.</div>
<div><br>
</div>
<div><span style="white-space:pre-wrap"></span>Ross</div>
<div><br>
<div><br>
Dr Ross Moore<br>
Department of Mathematics and Statistics
<div>12 Wally’s Walk, Level 7, Room 734<br>
Macquarie University, NSW 2109, Australia<br>
T: +61 2 9850 8955 | F: +61 2 9850 8114<br>
M:+61 407 288 255 | E: <a href="mailto:ross.moore@mq.edu.au" target="_blank">ross.moore@mq.edu.au</a><br>
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