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Diffstat (limited to 'Master/texmf-dist/doc/generic/FAQ-en/faq-wdidt.tex')
| -rw-r--r-- | Master/texmf-dist/doc/generic/FAQ-en/faq-wdidt.tex | 37 |
1 files changed, 19 insertions, 18 deletions
diff --git a/Master/texmf-dist/doc/generic/FAQ-en/faq-wdidt.tex b/Master/texmf-dist/doc/generic/FAQ-en/faq-wdidt.tex index ac786c10aab..97ab75e31a9 100644 --- a/Master/texmf-dist/doc/generic/FAQ-en/faq-wdidt.tex +++ b/Master/texmf-dist/doc/generic/FAQ-en/faq-wdidt.tex @@ -1739,35 +1739,32 @@ the problem. \item[AMSLaTeX]\CTANref{amslatex} \end{ctanrefs} -\Question[Q-dolldoll]{Why use \csx{[}\,\dots{}\csx{]} in place of \texttt{\$\$}\,\dots{}\texttt{\$\$}?} +\Question[Q-dolldoll]{Why use \csx{[}\,\dots{}\csx{]} in place of \texttt{\$\$}\,\dots{}\,\texttt{\$\$}?} \LaTeX{} defines inline- and display-maths commands, apparently -duplicating those that derive from the \TeX{} primitive maths -sequences, that maths commands with single (or pairs of) dollar signs. +duplicating the \TeX{} primitive maths sequences which surround maths +commands with single (or pairs of) dollar signs. -As it turns out, \LaTeX{}'s inline maths grouping, % !line break -\csx{(}\texttt{ ... }\csx{)}, has precisely the same effect as the -\TeX{} primitive version \texttt{\$ ... \$}. (Except that +In fact, \LaTeX{}'s inline maths grouping, % !line break +\csx{(}\texttt{ ... }\csx{)}, has (almost) exactly the same effect as the +\TeX{} primitive version \texttt{\$ ... \$}. (The exception: the \LaTeX{} version checks to ensure you don't put \csx{(} and \csx{)} the wrong way round; this does occasionally detect errors\dots{}.) Since this is the case, one often finds \LaTeX{} users, who have some experience of using \plaintex{}, merely assuming that \LaTeX{}'s display maths grouping \csx{[}\texttt{ ... }\csx{]} may be replaced by -the \TeX{} primitive display maths \texttt{\$\$ ... \$\$}. Some -people ``go the whole hog'' and use \cmdinvoke{begin}{displaymath} -\dots{} \cmdinvoke{end}{displaymath} (which ``looks nicer'', in some -sense, and actually \emph{describes} what's being done. - -Unfortunately, they are wrong: if \LaTeX{} code is going to patch display -maths, it can only do so by patching \csx{[} and \csx{]}. The most -obvious way this turns up, is that the class option \pkgoption{fleqn} +the \TeX{} primitive display maths \texttt{\$\$ ... \$\$}. + +Unfortunately, the assumption is wrong: some \LaTeX{} code needs to +patch display maths, it can only do so by patching \csx{[} and \csx{]} +(or their equivalents). Most obviously, the class option \pkgoption{fleqn} simply does not work for equations coded using % ! line break \texttt{\$\$ ... \$\$}, whether you're using the standard classes alone, or using package \Package{amsmath}. Also, the \csx{[} and -\csx{]} construct has code for rationalising vertical spacing in some extreme -cases; that code is not provided \texttt{\$\$ ... \$\$}, so if you -use the non-standard version, you may occasionally observe +\csx{]} construct has code for rationalising vertical spacing in some +extreme cases; that code is not provided \texttt{\$\$ ... \$\$}, so if +you use the \plaintex{} version, you may occasionally observe inconsistent vertical spacing. Similar behaviour can bite if you are writing a \emph{proof}; placing the ``\acro{QED} symbol'' doesn't work if it is in \texttt{\$\$}-displayed maths. @@ -1776,7 +1773,11 @@ There are more subtle effects (especially with package \Package{amsmath}), and the simple rule is ``use % ! line break \csx{[}\texttt{ ... }\csx{]} (at least) whenever displayed maths is needed in \LaTeX{}''. -\LastEdit{2013-02-20} + +(Note that the sequence \csx{[}\texttt{ ... }\csx{]} is duplicated by +the \environment{displaymath} environment, which can be said to ``look +nicer'', and actually \emph{describes} what's being done.) +\LastEdit{2013-06-05} \Question[Q-2letterfontcmd]{What's wrong with \csx{bf}, \csx{it}, etc.?} |