[latexrefman] Add Arrows subsection

Karl Berry karl at freefriends.org
Fri Nov 9 23:33:47 CET 2018

    Karl, what do we do about arrows such as \leadsto, which are not in
    standard LaTeX so the .pdf gives an error? 

There is no magic bullet (or arrow :). We will have to define them. Since
\leadsto (et al.) are just characters in the lasy fonts, it should be
easy enough to do. There are only about a dozen defined in latexsym.dtx.
(If I were still maintaining Texinfo, I would define them there, but I
wouldn't go that route now.)

I can work on this if you like, although if one of you wants to make the
plain TeX definitions to access them, so much the better. And/or, if
anyone could look up the Unicode code points (which I presume we'd want
for the HTML output), that would be great.

\DeclareMathSymbol\mho     {\mathord}{lasy}{"30}
\DeclareMathSymbol\Join    {\mathrel}{lasy}{"31}
\DeclareMathSymbol\Box     {\mathord}{lasy}{"32}
\DeclareMathSymbol\Diamond {\mathord}{lasy}{"33}
\DeclareMathSymbol\leadsto {\mathrel}{lasy}{"3B}
\DeclareMathSymbol\lhd     {\mathbin}{lasy}{"01}
\DeclareMathSymbol\unlhd   {\mathbin}{lasy}{"02}
\DeclareMathSymbol\rhd     {\mathbin}{lasy}{"03}
\DeclareMathSymbol\unrhd   {\mathbin}{lasy}{"04}

    I thought about putting
    in the AMS arrows, because they are pretty standard, but then I'd
    get two dozen errors.

They are AMS, not core LaTeX, and require \usepackage{amswhatever},
right? Same reasoning as usual; I wouldn't include them (now). The ams*
packages would surely be the first ones to add after core LaTeX is done,
but ... --thanks, karl.

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