How can I re-define a math operator / symbol?

Question

I'm new user and really need your help. I want to fix the size and position of a "math symbol". For example, I want to scale and adjust vertical position of symbol "+". According to information on internet, I try this way and it worked.

\documentclass{article}
\usepackage{graphicx}
\usepackage{amsmath}

\def\plus{\raisebox{0.13\height}{\scalebox{0.95}{$\mspace{4mu}+\mspace{4mu}$}}}

\begin{document}
\noindent
$1+2+3\\
1\plus 2\plus 3$
\end{document}

However, I wonder that how I can re-define the symbol "+" directly in the system without using syntax <\plus>.

I try to find more information, it leads me to "catcode". But I cannot apply it because of no knowledge about the syntax and structure.

note that the entire math setting is based on a "math axis" so - a fraction bar, and all operators such as < and > are all aligned on the same vertical position as the horizontal bar of the + so if you move that things will look unaligned. — David Carlisle, Jan 05 '20 at 16:43
See also: macros - How to redefine the "plus" symbol? - TeX - LaTeX Stack Exchange — user202729, Jun 13 '22 at 16:35

score 3 · Accepted Answer · answered Jan 05 '20 at 16:32

3

You could do as follows, making + math active.

\documentclass{article}
\usepackage{graphicx}
\usepackage{amsmath}

\makeatletter
\mathchardef\standardplus=\mathcode`+
\DeclareRobustCommand{\tauyecoplus}{%
  \mathbin{\mathpalette\tauyeco@plus\relax}%
}
\newcommand{\tauyeco@plus}[2]{%
  \raisebox{0.13\height}{\scalebox{0.95}{$\m@th#1\standardplus$}}%
}
\begingroup\lccode`~=`+ \lowercase{\endgroup\let~}\tauyecoplus
\AtBeginDocument{\mathcode`+="8000 }
\makeatother

\begin{document}

$1+2+3_{a+b}$ (modified)

$1\standardplus 2\standardplus 3_{a\standardplus b}$ (original)

\end{document}

answered Jan 05 '20 at 16:32

egreg

1,121,712

Thank you so so much! – Nuec Tah Jan 05 '20 at 17:54
excuse me, but how we can deal with other operator, like \times, etc. I cannot use similar syntax : \mathchardef\standardplus=\mathcode`\times – Nuec Tah Jan 05 '20 at 20:24
1

@Tauyeco You should first think deeply about modifying that way standard symbols: there are several reasons why they're shaped and positioned the way they are. – egreg Jan 05 '20 at 20:36
.@egreg: I know about the standard. But because of changing of math font, sometimes there are some symbols which don't have correct view. I just want to fix some small issues like above without changing so much. It's better if I can understand deeply, but currently I just have a little bit time.
Another question is, how I can know the list of all mathcode of symbol?
– Nuec Tah Jan 05 '20 at 20:52

How can I re-define a math operator / symbol?

1 Answers1

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