Re: [help-texinfo] Inserting text in tex math mode

[Karl Berry]

    However, there is no space after the text (with \r{if} or with \r{if
    }). I haven't researched why this is, but I expect it depends on the
    details of how @r is implemented in texinfo.tex.

It's not about @r (that just changes fonts). In TeX math mode, spaces
in the input are ignored, because TeX puts in its own spacing.

You could get a normal word space with
$$ \r{if } ... $$
but normally you don't want word spaces in math, but rather actual math
spacing amounts, e.g., \; for a so-called thick space, etc.

Really supporting display math in Texinfo (including xrefs) has been
on the todo list forever. Not to mention math itself. --happy hacking, karl.