Special double integral symbol - unable to find it in a4symbols list

Question

I have been using $\fint$ and $\iint$ for average integral and double integral respectively.

Is there a symbol which combines both, i.e $\iint$ with a horizontal line across as in $\fint$ ? I can't find one in the Comprehensive LaTeX Symbol List.

Edit: After the very helpful answer by Mico, I am trying to add a tilt to the horizontal dash. I do not understand the code by Mico well enough to be able to modify it.

Welcome to TeX.SX! Have a look at this answer showing how to insert a slash into a d, you could try it with \iint instead of d. — TeXnician, May 10 '17 at 04:31
Do you use any particular math font package or specialized symbols package (e.g., esint) for the \fint macro? — Mico, May 10 '17 at 05:03

Mico · Accepted Answer · 2017-05-10T10:36:15.573

(updated the answer to address the OP's follow-up request for a symbol with a tilted crossbar)

Here's a solution that builds on this answer. The names of the user macros are \fiint and \tiltfiint, respectively. In the code shown below, the angle of tilt is set at 15 degrees. Feel free to modify this setting to suit your taste.

If you happen to use a math font symbols package other than (or in addition to) amssymb, the double-integral symbol (\iint) will likely be spaced more tightly than is the case if just amssymb is loaded. If that's the case, simply replace the directive \def\longdash{-\mkern-3.5mu-} in the code below with either \def\longdash{-\mkern-5.5mu-} or -- especially if the esint package is loaded -- \def\longdash{-\mkern-7.5mu-}.

\documentclass{article}
\usepackage{amsmath}  % for \iint macro
\usepackage{graphicx} % for \rotatebox macro
\def\Yint#1{\mathchoice
    {\YYint\displaystyle\textstyle{#1}}%
    {\YYint\textstyle\scriptstyle{#1}}%
    {\YYint\scriptstyle\scriptscriptstyle{#1}}%
    {\YYint\scriptscriptstyle\scriptscriptstyle{#1}}%
      \!\iint}
\def\YYint#1#2#3{{\setbox0=\hbox{$#1{#2#3}{\iint}$}
    \vcenter{\hbox{$#2#3$}}\kern-.51\wd0}}
\def\longdash{{-}\mkern-3.5mu{-}} 
   % consider using "\mkern-7.5mu" if esint package is loaded
\def\tiltlongdash{\rotatebox[origin=c]{15}{$\longdash$}}
\def\fiint{\Yint\longdash}
\def\tiltfiint{\Yint\tiltlongdash}

%\usepackage{esint} %% optional
\begin{document}
$\displaystyle \fiint_u^v f$ 
\quad
$\fiint_u^v f$

\medskip
$\displaystyle \tiltfiint_u^v f$ 
\quad
$\tiltfiint_u^v f$

\end{document}

Thanks for the absolutely fantastic answer. This works exactly as I wanted. — Adi, May 10 '17 at 06:00

Special double integral symbol - unable to find it in a4symbols list

1 Answers1