symbols
What is a good way to get an O-times between the sizes of \otimes and \bigotimes? I should add that I want it to act as a math operator as in \bigotimes (so that I can use subscripts below it.)
I managed to get it by
\DeclareMathOperator*{\Motimes}{\raisebox{-0.25ex}{\scalebox{1.2}{$\bigotimes$}}}
using one of the approaches here:
A medium dot in math mode
I was wondering if there a better way?
The inspection of the math list happens after expansion (and after assignments). It is an extra stage just applicable to math mode that converts the math list into a horizontal list that is then typeset as a normal horizontal list.
So there is no real connection between the macro structure and the math spacing, It does not matter whether the thing to the left of the + has arguments or not, it just matters what it expands to (nothing in your example) so your example is equivalent to
\noindent
\( +x\) \\ % unary: "+x"
\( +x\) \\ % unary: "+x"
\({} +x\) \\ % binary: " + x"
\( +x\) \\ % unary: "+x"
\({} +x\) \\ % binary: " + x"
and as your comments show a binop like + gets binary spacing if it is between two mathord atoms such as {} or x.
Your example (from elsewhere, with \somecommand being a zero-argument macro)
\(\somecommand{} {+} x\)
is
\({} {+} x\)
Here the {+} construct makes a mathord so you get no spacing. My comment that this was probably bad markup was mainly related to the trailing {} after \somecommand it is OK to do that habitually in text mode to avoid dropping spaces but in math mode it's usually has an effect.
\(\somecommand{} {+ x}\)
is
\({} {+ x}\)
so here the math list has two, not three, mathord atoms: {} and +x. In this simple case it doesn't affect the spacing, but the inner expression is a single atom, so {+x} (and not x) would take any superscripts etc, and as it is an inner list linebreaking is suppressed and any white space is forced to its natural width (again not relevant here); basically in math node {...} is a box command like \hbox{....}.
There are in fact two choices for a unary math sign, a mathord or a mathop, it's easy to get an ad hoc mathord by using {+} but it is probably more consistent to declare the operators explicitly.
1 $a-+b$
2 $a-{+}b$
3 $a-\mathord{+}b$
4 $a-\mathop{+}b$
5 $x+y$
6 $x{+}y$
7 $x\mathord{+}y$
8 $x\mathop{+}y$
As you see from (1) if two binop atoms are adjacent the second one effectively turns into a mathord so you get the spacing as in (2) or (3) although arguably as a prefix operator giving it mathop spacing (with a small gap before its argument) is more consistent.
either way you don't want to be filling you document expressions with weird {} constructs and \mathxx primitives, just define
\unaryplus{{+}}
or whatever version you like and then use
a + \unaryplus b
and it will all work out OK.
In this case using directly \mathchoice seems preferable:
\documentclass{article}
\usepackage{fix-cm} % make font arbitrarily scalable
\usepackage{amsmath}
\newcommand{\malcev}{\mathbin{
\mathchoice
{\mbox{\normalsize\textcircled{\scriptsize M}}}
{\mbox{\normalsize\textcircled{\scriptsize M}}}
{\mbox{\scriptsize\textcircled{\tiny M}}}
{\mbox{\tiny\textcircled{\fontsize{3.5}{3.5}\selectfont M}}}
}
}
\begin{document}
\[
\mathbf{V} \malcev \mathbf{W} \qquad
F_{\mathbf{V} \malcev \mathbf{W}} \qquad
S^{\mathbf{V} \malcev \mathbf{W}^{\malcev}}
\]
\end{document}
Best Answer
With your declaration you get a symbol that is bigger than
\bigotimes...Assuming that you really want a symbol between the sizes of
\otimesand\bigotimesyou can declare it asThe following MWE shows the difference between it and
\bigotimesOutput: