[Tex/LaTex] Using there exists symbol within inference of the semantic package

semanticssymbols

I am using the semantic package to write inference rules. I need to put a there exists symbol which is standard to LaTeX using $\exists$ . However, when used within the semantic package's inference command as follows:

\inference[case$_0$]{$\exists$ I}{test}

several errors are encountered :

(./semantics.aux) (/usr/share/texmf-texlive/tex/latex/ucs/ucsencs.def)
! Missing $ inserted.
&lt;inserted text&gt;
$
l.42 \inference[case$_0$]{$\exists$ I}
{test}
! Extra }, or forgotten $.
\@processPremiseLine ...ce \end \hskip \@@pSpace }
\fi \fi \def \sem@tmp {#2}...
l.42 \inference[case$_0$]{$\exists$ I}
{test}
! Missing $ inserted.
&lt;inserted text&gt;
$
l.42 \inference[case$_0$]{$\exists$ I}
{test}
! Missing } inserted.
&lt;inserted text&gt;
}
l.42 \inference[case$_0$]{$\exists$ I}
{test}
[1] (./semantics.aux) )

Can anyone suggest what I can do please?

Best Answer

You can "box" the item using \ensuremath:

enter image description here

\documentclass{article}
\usepackage{semantic}% http://ctan.org/pkg/semantic
\begin{document}
\inference[case$_0$]{\ensuremath{\exists~I}}{test}
\end{document}

Note the forced spacing as a result of the tie ~. This may just be your preference, which I've stuck to.

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Suppose, purely for the sake of argument, that one were typesetting a book which had frequent occasion to reference publications by name --- Science, the New York Times and so forth. In a WYSYWYG editor, one would highlight the name of the journal and click the I button. With syntactic markup, like plain ol' HTML, one would wrap the journal name in codes indicating that it is to be italicized: <i>Science</i>. With semantic markup, by contrast, one could define a command which says, "This text is the title of a publication, and is to be handled in such-and-such a manner". Then, if one wished to change the style of the document, one could tweak the code defining that command, and the change would be reflected throughout, without having to modify each instance manually (and run the risk of missing something).

This has the added advantage that one can build extra features into the command. Instead of expanding out as "put this text in italics", the "publication name" command could do something more elaborate: "put this text in italics, and add the appropriate entry to the book's index". That way, a reader who wanted to find all the places where the book references a New Yorker article or an item in the IEEE Transactions on Love Poetry could just flip to the back and look up the pages.

The LaTeX implementation of that idea would look something like this, using the makeidx package to implement the indexing:

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Edit to add: Yes, this can easily become overkill. But it's fun!

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